A CRITICAL ANALYSIS OF HARBOUR TOWAGE OPERATIONS … · A CRITICAL ANALYSIS OF HARBOUR TOWAGE...

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Southampton Solent University

Warsash Maritime Academy Maritime and Technology Faculty

MSc in Shipping Operations

A CRITICAL ANALYSIS OF

HARBOUR TOWAGE

OPERATIONS RISKS TO

SAFETY.

Stephen Ford

31st

May 2013

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I. Abstract

Recent fatal harbour towage operational accidents highlight a potential safety concern. Initial investigation revealed a lack of empirical scientific research evidence regarding specific risks encountered during harbour towage operations. This project therefore sought to establish if harbour towage operations face particular risks. Comparison of harbour and non harbour towage operations indicated different risk profiles, with harbour towage accidents more likely to result in a collision involving loss of life. Statistical comparison of harbour towage and non harbour towage risk factors corroborated this. Certain risk factors were only present in harbour towage operations, and risk factor volumes were greater. Statistical testing of the relationship between individual risk factor and consequence significance also revealed a link. A number of risk factors were identified as influential in harbour towage operations; these ranged from safety management systems, tow planning, and interaction, to vessel speed, training and tug type. The research method employed, combining quantitative and qualitative surveying through triangulation, to objectively analyse and compare the data, demonstrated a degree of success; although a longitudinal methodology might better align frequency with likelihood, and better enable measurement of success of any intervention. The findings suggest a number of recommendations including, improved confidential hazardous event reporting, legislative reform to establish equitable regulatory oversight & monitoring, and enhanced training provision for individuals involved in harbour towage operations.

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Contents

Page

I. Abstract iv

Contents v List of tables & graphs vi

List of abbreviations viii

1.0 Literature Review 1 2.0 Methodology 6

2.1 Secondary data 8 2.2 Case Studies 9 2.3 Primary Data: Questionnaire 11 2.4 Grounded Theory 15

3.0 Results 18

3.1 Case Study Account 18 3.2 Questionnaire Account 22 3.3 Expert Interview Account 28 3.4 Comparison of Harbour Towage and Non Harbour Towage data 32 3.5 Hypothesis Testing: Chi Square test 37 3.6 Comparison of quantitative data 38 3.7 Risk Factors 45 3.8 Relationship between Risk Factor and Consequence Severity 48

4.0 Discussion 51

4.1 Suitability of Method 51 4.2 Harbour Towage versus Non Harbour Towage 53 4.3 Case Study versus Questionnaire Data 54 4.4 Risk Factor Quantity 57 4.5 Risk Factor Severity 57 4.6 Individual Risk Factor Account 58

5.0 Conclusions 63

5.1 Suitability of method 63 5.2 Analysis of risks to safety 64

6.0 Recommendations 67

6.1 Harbour towage operations reporting and research 67 6.2 Equitable regulatory oversight and monitoring 67 6.3 Enhanced training provision 68

7.0 References 69

Appendix A. A A-1 Example Harbour Towage Safety Questionnaire A

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List of tables and graphs Page

Table 1: Research Project Programme 7 Table 2: Questionnaire Sections 11 Table 3: Publicity Programme 12 Table 4: Questionnaire Distribution Groups 13 Table 5: Distribution of Case Studies 18 Graph 1: Apportionment of Accident Type 18 Graph 2: Apportionment of Event Consequence 19 Graph 3: Distribution of Tug Type 19 Graph 4: Distribution of Tug Bollard Pull 19 Graph 5: Distribution of Tow Position 20 Graph 6: Towed Vessel Type 20 Graph 7: Bow Form Distribution 20 Graph 8: Distribution of Towed Vessels Size 21 Table 6: Questionnaire Source 22 Graph 9: Safety Occurrence Description 23 Graph 10: Safety Occurrence Potential Result 23 Graph 11: Safety Occurrence Potential Consequence 24 Graph 12: Distribution of Tug Type 24 Graph 13: Distribution of Tug power 24 Table 7: Tug Power Categories 24 Graph 14: Tow Operation Type Distribution 25 Graph 15: Towed Vessel Category Distribution 25 Graph 16: Towed Vessel Bow Form Distribution 26 Graph 17: Towed Vessel Size Category 26 Table 8: Distribution of Towed Vessel Deadweight Categories 26 Graph 18: Prevailing Environmental Conditions 27 Table 9: Evidence Category: Speed, Interaction & Girting 28 Table 10: Evidence Category: Extreme Conditions 28 Table 11: Evidence Category: Legislation 28 Table 12: Evidence Category: Tow Planning & Command 29 Table 13: Evidence Category: Maintenance 29 Table 14: Evidence Category: Design & Complexity 29 Table 15: Evidence Category: Seamanship & Rope Management 29 Table 16: Evidence Category: Crewing 30 Table 17: Evidence Category: Stability 30 Table 18: Evidence Category: Fatigue 30 Table 19: Evidence Category: Training 30 Table 20: Evidence Category: Personal Qualities & Negative Attitudes 31 Table 21: Evidence Category: Time 31 Graph 19: HT to NHT Incident Category Comparison 32 Graph 20: HT to NHT Comparison of Consequences 32 Graph 21: Comparison of HT and NHT Towage Position 33 Graph 22: Comparison of Towed Vessel Type between HT and NHT CS 33 Graph 23: Comparison between HT and NHT Bow Form Distribution 34 Graph 24: Comparison of Towed Vessel Size 34 Graph 25: Case Study Comparison of Risk Factor Frequencies 35 Graph 26: Comparison of HT and NHT Risk Factor Volumes 36 Table 22: Chi Square Test Values 37 Graph 27: Comparison of CS and QU Events 38 Graph 28: Comparison of Consequence Frequency 38 Graph 29: Comparison of Tug Type 39 Graph 30: Comparison of Tug Power 39 Graph 31: Comparison of Tow Position 40 Graph 32: Comparison of Towed Vessel Type 40 Graph 33: Towed Vessel Bow Form Comparison 41 Graph 34: Towed Vessel Size Comparison 41 Graph 35: Comparison of Harbour Towage Risk Factors 42

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Graph 36: Rank Difference Case Study Versus Questionnaire 43 Graph 37: Additional Risk Factors identified in Case Studies 44 Graph 38: Comparison of Weighted and Un-weighted Risk Factors 45 Graph 39: Risk Factor Percentage Increase due to Perceived Importance 46 Graph 40: Risk Factor Rank Change due to Perceived Importance 47 Table 23: Pearson’s r Significant Number Values 48 Graph 41: Risk Factor Rank Movement 49 Graph 43: Risk Factor Frequency Variation 50 Table 24: Key Harbour Towage Risk Factors 65

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List of Abbreviations

ASD Azimuth Stern Drive [tug]

ATSB Australian Transport Safety Board

BTA British Tugowners Association

CS Case Study

DSB Dutch Safety Board

EI Expert Interview

EMSA European Maritime Safety Agency

HT Harbour Towage [operation]

ILO International Labour Organisation

IMO International Maritime Organisation

ITA International Tugmasters Association

KMSB Korean Maritime Safety Board

MAIB Marine Accident Investigation Branch

NHT Non Harbour Towage [operation]

QU Questionnaire

TSBC Transport Safety Board of Canada

UK United Kingdom

US United States of America (USA)

USCG United States Coastguard

VS Voith Schneider [tug]

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Glossary

Case Study Individual maritime safety agency accident report, analysed to extract harbour towage operations risk and safety data.

Expert Interview Qualitative interview (supported by written submission and

observational analysis) of expert witness experience of harbour towage operations safety.

Harbour Towage Movement, berthing or unberthing of a vessel with the assistance of a Operation tug(s) within a harbour, port or equivalent area.

Girting (Also similar: Girding and Tripping). Where a vessel is caused to

potentially capsize, most commonly as a result of external towline and

interaction forces.

Interaction Hydrodynamic forces commonly found immediately adjacent to a

vessel moving through the water.

Non Harbour Any operation or activity other than harbour towage, involving a tug(s) Towage Operation carried out in any sea area.

Questionnaire Survey of current practitioners experience of harbour towage

operations safety, using a Likert style questionnaire (See Appendix A).

Risk Factor An element whose presence or absence has potential to lead to lead

to an unsafe event.

Tow Planning Planning and management of a harbour towage operation, commonly

undertaken by a licensed pilot.

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The Transport Safety Board of Canada (2013) report’s that, tugs & barges along with Bulk

carriers, ‘were involved most often in accidents’1 (thirteen percent). This includes having the

highest number of fatalities and the highest number of accidents aboard ship.

While it might be argued that this is due to a highly developed river tug sector in Canada, the

Australian Transport Safety Board (2011) shipping occurrence statistics showed that eight

percent of collisions, ten percent of contact damage and seventeen percent of capsizing,

involved tugs.

Well publicised, but tragic harbour towage accidents include:

19th July 2012, the Tug Madison was capsized by her tow, the dredge barge

Arthur J., on Lake Huron (USCG, 2012);

12th August 2011, the tug Chieftain capsized with the loss of one life, off Convoys

Wharf on the River Thames, while towing the crane barge Skyline (MAIB, 2012

A);

11th June 2011, the tug Adonis, while engaged in moving the barge Chrysus, in

Gladstone, was capsized with the loss of one life (ATSB, 2013);

11th November 2010, the tug Fairplay 22 capsized with the loss of two lives, in

gale force winds off the Hook of Holland, while making fast to the Stena

Britannica (DSB, 2010).

Henson (2012) points out that, ‘tug operations near the bow of a ship having headway are

very risky; the higher the ship’s speed, the larger the risks’. Dand (1975) reporting on ship

model tests said that, ‘interaction forces varied with the square of the speed; and near the

fore body of a ship the tug may drive itself under the bow’.

A Dutch Safety Board (2010) report into the fatal collision and capsize of the tug Fairplay 22,

concluded that, ‘the tug had sailed close to bulbous bow, and within the hydrodynamic

sphere of influence; here it was unable to maintain a safe distance and collided with vessel’.

1 Excludes Fishing Vessels.

1.0 Literature Review

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The British Tug Association (2010a) described an example of the associated risk of Girting

where, ‘a tug acting as brake while assisting the berthing a barge started an uncontrolled

yaw, leading to her capsize and foundering’.

The New Zealand Transport Accident Investigation Commission (2001) report into the

capsize and sinking of the tug Nautilus III, point out the importance of adequate Tow

Planning in the prevention of harbour towage accidents.

MAIB (2012) reporting on the fatal accident to the Chiefton supported this view, pointing out

that ‘the passage plan centred almost entirely on the bridge transit phases and did not

properly consider the need for river passage planning or its related risks’.

Referring to the same accident, MAIB highlighted the importance of the development of

adequate Safety Management Systems. They concluded that, ‘there was no evidence that

the tug operating company had conducted formal risk assessments of their vessels’

operations; the watertight integrity discipline on board Chiefton was weak; and, the

functionality of Chiefton’s towing hook release system was in doubt’.

Kunze (2011) talking at the British Tugowners Association’s Safety Seminar, underlined the

importance of Training, highlighting how ship simulators can provide opportunity for tug

masters to, ‘gain competence and confidence’. The 2012 BTA Safety Seminar again

highlighted the importance of Training, ‘delegates citing continued instances of poor

seamanship observed onboard assisted vessels, leading to dangerous occurrences for tugs’.

Stockman (2010) in his report on the near girting and capsize of the tug Stockton II,

underlined that Following Operational Procedures can be critical to safety. He pointed to

video footage of the incident illustrating, ‘as the tug heeled over with its doors pinned open,

had the tow rope not parted, the results of the incident could have been far more serious’.

The USCG (2009) Marine Safety Information Bulletin, dealing with reducing ‘Downstreaming’

safety incidents, underlines the critical importance of adequate Tug Handling.

Lack of manoeuvring space is also a risk to safety during harbour towage operations, as

highlighted by BTA (2010b) in their description of a collision between a tug and a vessel

while operating in a narrow channel.

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The European Harbour Masters committee (2010) identified concern over the issue of ship

size, stating that Pilots and tug captains are ‘increasingly facing operational problems

handling ever growing ship sizes’.

Henson (2011) in Safe Tug Procedures underlines the importance in choice of tug type, to

help ensure safety of operations. He points out, ‘if tugs with propulsion units aft are very

close to the ship’s bow, to get clear by steering away, the tug’s stern will come closer to the

ship, increasing the suction forces and consequently the risk of hitting the bow’.

The Australian Transport Safety Board (2006) identify risks from lack of maintenance in their

report (No. 224) into a collision between a bulk carrier and a tug. They conclude that, ‘a

crack in the tug’s starboard main engine clutch oil discharge pipe, led to the engine’s

shutdown; this caused the tug’s stern to swing sharply to starboard, making heavy contact

with the ship, and puncturing the ship’s shell plating’.

The New Zealand Transport Accident Investigation Commission (2000) underlined the

importance of communications in harbour towage operations safety. In their report into the

man overboard and near capsize on a tug, they identified the safety issue of, ‘poor

communication between bridge team and crew at mooring stations; and insufficient

communication between tug skipper and pilot’ leading to the unsafe situation.

Livingstone (2012) in The International Pilot, points out the risk that environmental conditions

can place on harbour towage safety. In the fatal accident when the tug Flying Phantom was

girted and sank, thick fog may have led to a disorientation of the tug crew.

A joint paper produced by the European Tugowners and the European Pilots Associations’

(2011) demonstrates how advances in vessel design may produce risks to harbour towage

safety. They point to the, ‘operational problems European pilots and tug operators have

increasingly experienced over the last decade relating to the type and strength of deck

equipment on board of ships’; this highlights a contradiction posed by increased tug bollard

pull, versus moderated bollard structural strength.

Legislation with respect to harbour towage operations is complex, tending to cascade from

IMO (2013) International Conventions. Principle treaties include, the International

Convention for the Safety of Life at Sea (SOLAS) 1974; the International Convention on

Standards of Training, Certification and Watchkeeping for Seafarers (STCW) 1978; and the

International Convention on Load Lines 1966.

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The Canada Shipping Act 2001, Load Line Regulations (SOR/2007-99) and the Safety

Management Regulations (SOR/98-348) have been used to ratify conventions at Canadian

state level. In the United Kingdom (UK) the Merchant Shipping Act 1995, the Merchant

Shipping (Load Line) Regulations 1998 and Merchant Shipping Notices 1812 & 1826

(SOLAS) interpret international codes; while in the United States of America (USA) US Title

33 (Navigation and Navigable Waters) and Title 46 (Shipping) are examples of ratifying

legislation.

While this legislative framework can benefit safety of harbour towage operations, tugs can

also fall below Gross Tonnage thresholds for many international conventions. Although

companies investigated by the author voluntarily complied with SOLAS Chapter IX

(Management for the Safe Operation of Ships) there is no legal requirement for vessels

under five hundred Gross Tonnes to operate Safety Management Systems.

Equally, in the three states examined the Load Line Regulations applied to vessels of 150

gross tonnes (GT) or more, and 24 m or more in length; this may create exceptions for

certain vessels engaged on sheltered waters voyages, and exclude particular categories of

tug.

While the Maritime Labour Convention 2006 (ILO, 2013) makes provision for suitable hours

of rest for mariners, in the United Kingdom, ‘MSN 1767 Hours of Work, Safe Manning and

Watchkeeping Regulations, do not apply to ‘seafarers engaged on tugs in categorised

waters’.

Ratification of International legislation at state level, can also create opportunity for variation

in interpretation. The UK Boatmasters’ Regulations [SI 2006 No. 3223] creates a licensing

system for tugmasters of vessels falling outside conventional legislation (under Workboat

Codes). The UK Port Marine Safety Code facilitates ports to develop management systems,

supporting safe tug operations: the port of Heysham (2011) creating the ‘Minimum safety

standards for tug boats operating within the port’s jurisdiction’. However this legislative

programme is not universal, to all states engaged with harbour towage operations.

Positive progress was witnessed in non legislative spheres, with improved understanding of

technical aspects. Henson (2012) points out that proper tow planning can improve safety of

operations; proposing that the use of ‘Tractor tugs, and tugs with propulsion units forward,

are much safer to operate as bow tugs, as they can better compensate for the interactions

forces’.

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In a combined report with Merkelbach and van Wijnen (2013) following a comprehensive

international survey, they highlight the importance of maintaining ‘a safe speed’, with ‘all

parties following correct and safe procedures, when making a towline connection’.

New tug designs such as the EDDY are being developed, with one thruster forward and one

aft in order to improve handling; while new towing systems are in operation, such as the

Rotor, which helps minimise towline friction.

In addition to safe speed and safe procedures Henson, Merkelbach and van Wijnen (2013)

identify the importance of ‘comprehensive training underpinned by experience, for tug

masters, pilots and ship’s captains, ensuring optimum team working between all those

involved in safe harbour towage operations’.

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The object of this research was to identify and quantify independent variables causing a

threat to harbour towage safety, the dependent variable.

The difficulty of sampling a population not involved in safety incidents, in order to establish a

control group, raised investigative problems. Experimental research would be an ideal

methodology; however, it would not be practical or ethical to have accidents under controlled

conditions, in order to determine Risk Factors.

Analytical survey, through exploration of associations between variables, was therefore

considered a more appropriate choice; however, since a population studied may represent a

particular segment, the methodology would need to allow for statistically skewed

distributions.

As an exploratory non experimental project, the research was not able to follow a highly

structured deductive approach and control variables to generate data for analysis. The

project therefore also relied upon a Phenomenological approach, gathering contextual

descriptions of people’s experiences, and as an open ended enquiry using active

experience, it contained Heuristic elements.

The survey, sampling over a discrete 3 month period was cross-sectional; however because

it also relied upon data collected over a period of ten years it incorporated longitudinal

qualities.

The project used an Interpretivist perspective, employing Multiple Methods to triangulate

results, and was divided into six phases (See table 1.) to allow analysis and production of a

report by June 2013.

The three research methods used were:

1. Grounded Theory (Marshall, 1996) qualitative Interview and observational analysis of

expert witness opinion;

2. Quantitative sampling analysis of existing accident Case Study data;

3. Questionnaire survey of practitioners’ professional experience.

2.0 Methodology

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Phase Activity Completion date

One Production of Research Proposal 26/10/2012

Two Planning of the project 16/11/2012

Three Research literature review 28/11/2012

Four Collection of primary and secondary data 28/01/2013

Five Analysis and interpretation of data 30/03/2013

Six Production of research report 31/05/2013

Table 1: Research Project Programme.

The first stage involved interviews of experts. Data was then analysed using Grounded

Theory coded analysis (Calman, 2011) to provide a depth of perspective.

The second stage consisted of an analysis of secondary data (University of Southampton,

2012) followed by statistical testing, to establish any correlation. The use of ninety case

studies (thirty each from three separate states) aimed to reduce sampling error.

The third stage consisted of a questionnaire survey of current practitioners. This used a

Likert style questionnaire (Social Research Methods, 2006) to enable comparison of

independent variables and to cross check results. Its purpose was to provide specific

contemporary figures, to help identify patterns of safety incident type, cause, result,

frequency and criticality.

During the process, safety Risk Factors were identified, critically evaluated and categorised.

Their likelihood and severity were measured, and this information was used to test

hypotheses.

Since each technique was different, some adjustment was necessary to enable comparison

of the three separate samples and allow triangulation (Holtzhausen, 2001) to help validate

conclusions.

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2.1 Secondary data

2.1.1 General

The project employed two stages of secondary data collection. The first stage was a

preliminary exploration of the issues, to ensure a full range of incidents and factors were

investigated. The second stage involved collection of a portfolio of Case Studies from the

databases of three flag states.

2.1.2 Textbooks, journals and articles

A mixture of textbooks, journals and articles were investigated. This included Maritime

Safety Agency, tug company, harbour authority and other organisation safety incident

reports (MAIB, 2012; DSB, 2011). Manuals and professional books provided specialist

technical advice on safety risk factors and best practice guidance (Slesinger, 2010;

Livingstone, 2006). Trade and industry journals afforded additional expert opinion and

contextual information (International tug and OSV Magazine, 2013).

2.1.3 Internet

Internet search-engines, databases, and news agencies were used to access current

information (Intute, 2006). The Internet was also used to investigate university library,

government and company databases (KMSB, 2012; EMSA, 2012).

In addition, the internet provided a means to contact organisations & individuals, and to

dispatch documents (International Tug masters Association, 2012; UK Harbour Masters

Association).

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2.2 Case Studies

2.2.1 General

It was considered impracticable to survey every state in the time scale available; three states

were therefore selected from a shortlist thirty four, using criteria including:

possession of a maritime border and an established port system;

provision of a readily accessible maritime administrative system;

has globally representative characteristics;

translates safety reports in to English.

The final selection, providing representation of harbour towage operations accidents, were:

Canada;

United Kingdom;

United States of America.

2.2.2 Development of the Harbour Towage Safety Risk: Excel

Spreadsheet Proforma

An Excel spreadsheet template was developed to gather data on risks to safety in harbour

towage operations; three example maritime safety agency incident case studies and a

United Kingdom Marine Accident Investigation Bureau accident data sheet, provided a

model of potential factors.

2.2.3 Populating the Excel Spreadsheet

Detailed data on risks to safety were collected from thirty most recent and available accident

case studies, in three separate states. This information was critically analysed, to ensure

data quality and validity:

only Case Studies produced by government safety agencies were accepted;

incident dates and names were cross checked to prevent duplication.

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The following generic data was gathered from each of the Case Studies and entered on to

the Excel Spreadsheet:

General incident and vessel particulars (date, vessel name, Gross Tonnage & length

overall);

Incident type and consequence (collision or grounding; damage or injury);

Prevailing environmental conditions (weather & sea state);

Towage operation particulars (tug type & tow point);

Findings concerning analysis, causes and conclusions (contributing factors, risks &

potential solutions).

Risk Factors were grouped under generic headings developed from maritime safety agency

reports. Where the lack of a particular factor was reported as a cause, then this would be

recorded; for example, if inadequate safety management systems were identified, this would

be recorded as Risk Factor: ‘Safety Management System’.

Any inapplicable cases studies were identified and removed, where they contained

insufficient verifiable facts.

Remaining case studies were categorised non harbour towage if they were engaged in, for

example:

deep sea towing;

not engaged in towing.

The applicable case studies were then statistically analysed, compared and triangulated with

the other surveys.

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2.3 Primary Data: Questionnaire

2.3.1 General

A questionnaire approach was selected to gather primary data because it:

provided a systematic quantitative measure, describing, comparing and explaining

contemporary factors effecting harbour towage operations safety (Sapsford, 1999);

enabled gathering large volumes of information over a short time period, from across

the globe.

The questionnaire process was planned to ensure systematic data collection; efforts were

made to standardise the process and eliminate error, by following set procedures and

keeping robust records.

The questionnaire was divided into five sections (See Table 2.). Most questions were

closed, dealing with factual, measureable information; although there were opportunities to

provide additional alternatives or descriptive facts.

Section five used a unipolar, Likert, forced choice, response scale, to grade degree of

applicability. This was chosen to reduce selection of a middle ‘neutral’ option, and to

motivate greater consideration of all explanations.

Section Content

One Instructions and further information concerning the research project.

Two Factual details concerning the particular harbour towage operation.

Three Environmental factors affecting the operation.

Four Details of the risk or safety issue encountered.

Five Risk Factors considered to be causing the risk or safety issue.

Table 2: Questionnaire Sections.

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2.3.2 Process

A pre-test survey was conducted, by providing the draft questionnaire to two non-

participants, to check for comprehension, construction and clarity. Research ethics for the

whole project, were addressed using the Solent Research Ethics Release (2013) process.

To maximise participation, a publicity plan was produced (See Table 3.). This enabled

identification of potential sources and methods to advertise the project, together with

timetabling of target dates. Any publicity through conventional media, with its long lead-time,

necessitated prompt production of promotional material. The Internet and electronic

communications media were however key to ensuring global participation, in the short time

frame available.

Target group Method of publicising Deadline

Harbour Towage

Organisations

Direct email, provision of electronic questionnaire, and

follow-up correspondence to relevant organisations.

10/11/2012

Professional

Mariners

Contact Maritime Media Companies, with a press

release and follow up correspondence.

10/11/2012

Pilotage

Organisations


follow-up correspondence.

20/11/2012

Harbour Towage

Companies


follow-up correspondence.

20/11/2012

Other Web-site, for provision of research project information

and questionnaires.

30/11/2012

Reactive Contacts Direct provision of questionnaire. 28/02/2013

Table 3: Publicity Programme.

To properly organise administration, with its reliance upon electronic communications,

setting up of a dedicated e-mail facility was required: [email protected]

Creation of a “Tug Safety” research project web-site helped authenticate its provenance and

supplied information to participants: http://mahara.solent.ac.uk/view/view.php?id=66091

http://mahara.solent.ac.uk/view/view.php?id=66091

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2.3.3 Target Participation

In consultation with the Solent University Research Project Co-ordinator, a target of 30

questionnaires was decided, as valid and practicable. To achieve this, the questionnaire

was distributed to a stratified group of one hundred and thirty five interested organisations

and individuals (See table 4.).

Group Total questionnaires distributed

Class surveyors 5

Harbourmasters 20

Maritime Administrators 5

Marine Insurers 5

Maritime legislators 5

Pilots 20

Ship’s crews 20

Towage Company Managers 10

Tug crews 30

Tug interest organisations 10

Tug shipbuilders 5

TOTAL 135

Table 4: Questionnaire Distribution Groups

All participants were volunteers, who were informed of the purpose of the project and no

pressure was applied to participate. To ensure privacy, the researcher was the only person

to contact participants, and submissions were entered on to a single computer, to which only

the author had password access. No copies of submissions were made, no details were

released to third parties, and all submissions are to be destroyed on 30th July 2013.

There were three main means of participation:

participants could receive a questionnaire forwarded from their employer or

professional body;

a questionnaire could be sent electronically from the ‘Tug.Safety’ e-mail account;

a questionnaire could be downloaded from the Tug Safety web-site.

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2.3.4 Quality Control

While without password protection there was less control over respondents, potentially

reducing data validity, this had to be balanced against the practicalities of maintaining a

global response. To mitigate this, contact details of participants were kept for subsequent

validation, should this prove necessary.

Response reliability may have been increased, and socially desirable response bias

reduced, through the anonymity of online surveying. Use of a global population may have

reduced sampling error, diversifying the population and randomly distributing any errors; this

was particularly important as volunteers, rather than a random sample, might increase

potential for skewed distributions.

Questionnaires were self administered, using instructions contained on the questionnaire

and returned directly to the dedicated e-mail account for analysis (See Annex A.). On

receipt of completed questionnaires, an acknowledgement was sent, together with details of

how follow-up information could be obtained.

2.3.5 Analysis

Each Questionnaire was assigned a unique reference number and the data was cleaned

(checking for obvious errors & ineligibility). The data was then collated and coded for

quantitative analysis on an Excel spreadsheet.

Each Likert item was treated as ordinal data and analyzed separately; when using only four

significance levels, it could not be assumed that respondents perceive the difference

between adjacent levels, as equidistant. If treated as ordinal data, Likert responses could be

analyzed using non-parametric testing.

Data from the Questionnaire survey was combined on the Excel spreadsheet, with that from

the Case Studies. The process used the same format as the Case Studies to enable direct

comparison between surveys.

http://www.answers.com/topic/level-of-measurement

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2.4 Grounded Theory

2.4.1 General

A Grounded Theory interview qualitative research process was selected because:

in contrast with the other techniques it was explicitly emergent; it did not test a

hypothesis, but set out to find what theory accounts for a situation (Dick, 2005);

it allowed the study of social interactions & behaviour, measuring attitude & opinion,

as integral factors;

it allowed an in-depth exploration of this relatively new area, where previous research

was limited.

The first stage of the process, involved a literature review. The interview process and

analysis were then planned, to establish systematic sampling and data collection. The

interview process was then pre-tested and all equipment was checked.

A Judgement sample of expert interviewees was targeted: those with over twenty five years

professional experience (a period during which practitioners might reasonably be expected

to have encountered a range of harbour towage operations safety issues). To maximize

variation in experience and avoid subject bias, experts from contrasting operations,

management and regulatory roles were selected, from:

Tug Handlers;

Harbour Pilots;

Harbourmasters;

Maritime Legislators.

All interviewees were volunteers and no pressure was applied to participate. Before

interviews commenced, the process was risk assessed (following Solent University

Guidelines) and interviewees were informed of the purpose of the project.

To ensure confidentiality, only one transcript was produced for each interview, this was

maintained as a controlled document, and no details of interviewees were released to third

parties.

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2.4.2 Process

Initial contact was made with potential expert interviewees; if they agreed to participate, a

date was decided for subsequent interview. On the agreed date the interview was

conducted, following recommended guidelines (Tellis, 1997).

At this stage, it was not possible to specify a particular sample size, since Grounded Theory

requires repetition, until new data no longer provided new information; a point called

theoretical saturation (Glasser & Strauss, 1967).

Interviews with experts were held, either face to face or over the telephone, and lasted about

45 minutes. The interviews were recorded using audio equipment, allowing the interviewer

to focus on the conversation; recordings were subsequently transcribed for analysis. Back-

up notes were also taken to highlight particular points. Following interview, participants were

thanked and provided with an address to obtain further information.

Interviews were semi-structured, with the participant asked to describe and reflect upon

experiences of harbour towage safety, using a series of short, clear prompt questions,

concerning tug operations and potential threats to safety, where necessary. The participant

was active while the interviewer listened actively.

They commenced with ‘Open-ended Questions’ (Charmaz, 2006) concerning the experts

background and views on harbour towage safety. ‘Intermediate Questions’ then probed

deeper into safety issues, and ‘Ending Questions’ elicited any concluding remarks.

Interview process and analysis were simultaneous; the first interview provided an initial

question framework, while subsequent interviews evolved iteratively, allowing enquiry to

focus upon apparent patterns (Hoda, 2011). Emerging codes, concepts, and categories

helped structure and systematically capture information from subsequent interviews (Strauss

and Corbin 1994). Written transcripts provided additional observations, further insight and

validation of themes.

During coding, the transcript data was read through several times to get a general

impression and to identify the major ideas, unusual events and deviant cases. It was then

progressively ‘chunked’ into sentences or phrases, to allow ‘Open Coding’ (Hallberg, 2006).

17

Constant comparison was used to ‘Selectively Code’ material into concepts, and to identify

‘Core Categories’ (central themes, reoccurring most frequently, and related to main

categories). The text was systematically marked with the codes or categories, and this

process was repeated several times, until ‘saturation’ was reached. Finally axial coding of

the transcripts was used to compare, identify and verify connections or relationships

between categories and concepts.

Analysis and coding was completed before other data sets were examined, in order to keep

an open mind and so reduce preconceptions. Once the interviews had been coded and

categorised the resulting Grounded Theory was triangulated with the other research

techniques.

18

3.1 Case Study Account

A total of ninety Case Studies (CS) were selected; thirty each from three states. Five CS

were inadmissible through insufficient validation (See Table 5.). Of the eighty five

admissible CS, fifty eight were classified as Harbour Towage (HT) and the remaining twenty

seven Non Harbour Towage (NHT).

State Inadmissible

Case Studies

Harbour

Towage

Non Harbour

Towage

Total

Canada 1 20 9 30

United Kingdom 0 20 10 30

United States of

America

4 18 8 30

Total 5 58 27 90

Table 5: Distribution of Harbour Towage and Non Harbour Towage Case Studies

Ninety five percent of the CS were classed as Accidents; of the remaining CS one was

classed an Incident, one a Near Miss and two as Other2. Thirty nine of the CS involved

Collision, twenty four Capsize and twenty Grounding (See Graph 1.).

Graph 1: Apportionment of Accident Type (number)

2. Figures may exceed total Case Studies, since one event may lead to several consequences.

39

20

24

3

6 Collision

Grounding

Capize / Founder

Fire

Other

3.0 Results

19

Analysis of incident consequence indicates that seventy two resulted in Damage, thirty three

in Injury and twenty in Loss of Life (See Graph 2.).

Graph 2: Apportionment of Event Consequence (number)

Analysis of the towage operation indicated, fifty four percent concerned Conventional tugs,

while thirty five percent were an undetermined tug type (See Graph 3.).

Graph 3: Distribution of Tug Type (percentage)

Forty eight percent of tugs were Moderately powered (See Table 7) while twenty three

percent were Medium powered or were Unspecified (See Table 4.).

Graph 4: Distribution of Tug Bollard Pull (percentage)

20

33

9

72

Loss of Life

Injury

Pollution

Damage

54.1

4.7

5.9

35.3

Conventional

ASD

VS

Unknown

48.2

23.6

4.7

23.5

Moderate (<30t)

Medium (31-65t)

High (>65t)

Unspecified

20

Forty four percent of events involved Towing from Forward, twenty percent Pushing, while

twenty two percent were unspecified (See Graph 5.).

Graph 5: Distribution of Tow Position (percentage)

The majority of events (forty six) concerned barges (See Graph 6.).

Graph 6: Towed Vessel Type (number)

The majority of towed vessels (sixty seven percent) had broad bow forms (See Graph 7.).

Graph 7: Bow Form Distribution

44.7

8.2

20

22.4

4.7 Tow fwd

To aft

Push

Other / unknown

Amidships

12

9

46

18

Tanker, Bulk Carrier etc.

Container, RoRo, General Cargo, etc.

Barge

Unspecified

10.6

67.1

22.3

Fine to Moderate

Broad

Unspecified

21

The majority of towed vessels (fifty percent) were classed Small (under 10,000 tonnes

deadweight) while eleven percent were Handy (See Table 8) or were Large (MAN, 2007).

There were no Very Large vessels (over 160,000 tonnes deadweight) while twenty five

percent were of unspecified size (See Graph 8.).

Graph 8: Distribution of Towed Vessels Size (Deadweight Category: percentage)

50.6

11.8

11.8

0

25.8

<10K t

10-50K t

51-160K t

>160K t

Unspecified

22

3.2 Questionnaire Account

Thirty two questionnaires were received by email; nineteen of these were submitted by Tug

Masters, nine by Pilots and four by Ship’s Masters. Submissions were received from

fourteen countries (See Table 6.) and all were considered valid.

Table 6: Questionnaire source

Analysis of the Mean, Median, Mode and Standard Deviation indicated that the data was not

Normally Distributed, with a sample Risk Factor frequency histogram plot indicating a

positive skew.

State Number of

questionnaires

Australia 3

Belgium 1

Chile 1

Finland 1

Ireland 1

Italy 4

Latvia 1

Netherlands 2

New Zealand 2

Poland 1

Portugal 1

Singapore 1

United Kingdom 7

United States 1

Unknown 5

TOTAL 32

23

Sixteen of the Questionnaires concerned Near Misses, there were seven Incidents, five

Challenging operations, three Accidents and one questionnaire was categorised Other (See

Graph 9.).

Graph 9: Safety Occurrence Description (number)

Questionnaire potential for Collision was eighty seven percent, Grounding thirty seven

percent and Capsize or Foundering thirty four percent3.

Graph 10: Safety Occurrence Potential Result (percentage)

3. Figures total over one hundred percent, since a single safety occurrence can lead to multiple results.

5

16

7

3 1

Challenging

Near Miss

Incident

Accident

Other

87.5

37.5 34.8

0 3.1

0 20 40 60 80

100

Pe

rce

nta

ge P

ote

nti

al

Event

24

A breakdown of consequences from a safety occurrence includes ninety three percent

potential for Damage and sixty eight percent potential for Injury. There was fifty percent

potential for Loss of Life, with sixty five percent potential for Pollution (See Graph 11.).

Graph 11: Safety Occurrence Potential Consequence (Average Likelihood)

Eighteen of the Tugs described were Azimuth Stern Drive (ASD) eight were Conventional,

five had Voith Schneider propulsion systems and one was Unspecified (See Graph 12.).

Graph 12: Distribution of Tug Type (number)

Twenty eight percent of tugs were Moderate (See Table 7.) fifty nine percent Medium and

nine percent were High powered (See Graph 13). All of the Conventional tugs were

Moderate powered, while all except two of the ASD tugs were Medium powered.

Graph 13: Distribution of Tug Power Table 7: Tug Power Categories (percentage)

50

68.8 65.6

93.8

0 20 40 60 80

100

Loss of Life

Injury Pollution Damage

Po

ten

tial

(p

erc

en

tage

)

Consequence

8

18

5

1 Conventional

ASD

VS

Unspecified

28.1

59.4

9.4 3.1

Moderate (<30t)

Medium (31-65t)

High (>65t)

Unspecified

Tug Power Bollard

Pull (BP):

tonnes

Moderate < 30

Medium 31 - 65

High >65

25

Ninety four percent of safety occurrences involved use of a line (either Push/Pull or Towing

on a Line); ninety one percent of cases were using the Tug’s Line (See Graph 14.).

Graph 14: Tow Operation Type Distribution

Thirty seven percent of vessels were categorised Container, RoRo or General Cargo, twenty

five percent were Tankers, Gas or Bulk Carriers, three percent were Barges and the

remainder were Unspecified (See Graph 15.).

Graph 15: Towed Vessel Category Distribution

56.2 37.5

6.3

0 20 40 60

Pe

rce

nta

ge

Tow Type

34.4

3.1

25

37.5

0

5

10

15

20

25

30

35

40

Fre

qu

en

cy (

pe

rce

nta

ge)

Vessel Type

26

Thirty four percent of vessels had fine formed bows, twenty one percent moderate and

twenty eight percent were broad bowed (See Graph 16.).

Graph 16: Towed Vessel Bow Form Distribution

Twelve percent of Towed Vessels were Small (under ten thousand tonnes Deadweight) and

Very Large (See Table 8) thirty one percent were Large, twenty eight percent Handy, and

sixteen percent were of Unspecified size (See Graph 17 and Table 8.).

Graph 17: Towed Vessel size Category Table 8: Distribution of Towed

Vessel Deadweight Categories

(MAN, 2007)

15.6

34.4

21.9

28.1

0

5

10

15

20

25

30

35

40

Fre

qu

en

cy (

pe

rce

nta

ge)

Bow Form

15.6 12.5

28.1

31.3

12.5

0

5

10

15

20

25

30

35

Fre

qu

en

cy (

pe

rce

nta

ge)

Vessel Size (thousand tonnes Deadweight)

Towed

Vessel

Size

Category

Deadweight

(tonnes)

Small <10,000

Handy 10,001 – 50,000

Large 50,001 –

160,000

Very Large > 160,000

27

Environmental conditions varied; Modal wind states were Moderate (between Beaufort Wind

Force four and six). Modal swell conditions were Calm (under 0.2m swell height); although

they were categorised Rough (1 to 1.5m) on six percent of occasions and Heavy (over 1.5m)

on nine percent of occasions. Modal current conditions were Low (less than 1 knot) with

Moderate current on nineteen percent and Strong current on nine percent of occasions. Fog

was present on nine percent of occasions (See Graph 18.).

Graph 18: Prevailing Environmental Conditions

0

1

2

3

4

5

6

7

8

9

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Me

asu

rem

en

t

Questionnaire No.

Wind Strength (Beaufort Force) Swell Height (metres) Current Strength (Knots)

28

3.3 Expert Interview Account

Five Experts were interviewed. Interviewees had between twenty seven and fifty two years

employment experience in maritime operations; roles performed included as Tug Master,

Ship Master, Harbour Master, Pilot, Superintendent, Regulatory Surveyor, Class Surveyor

and Marine Consultant.

Speed, Interaction and Girting: Experts identified vessel speed as a critical risk factor,

(and associated with this, the effect of interaction); the faster the vessels, the less safe the

operation, and the increased potential for interaction or girting.

Code Sample statement

Speed &

Interaction

“speed is a big factor, due to interaction, it is a major cause…”

Girting “[girting] still cont. to happen, even though there are ways of reducing the

probability, it continues to occur…”

Table 9: Evidence Category: Speed, Interaction & Girting

Extreme Conditions: Experts identified extreme environmental conditions as a

critical risk factor; in particular physical limitations posed by proximity to vessels & structures,

and the effects of swell, wind, current & fog.


Swell “every towline breaking with me , it’s been swell conditions, snatching …”

Proximity “thrusters are a problem [making] it difficult to maintain position & stop

yourself from being washed away…”

Wind /

current

“… it was not long before I realized that the four tugs could not hold the

vessel, and that we were being blown to ….”

Table 10: Evidence Category: Extreme Conditions

Legislation: Lack of regulatory oversight was identified as a particular risk to

safety; with potential for unclassified vessel’s to go unmonitored.


Legislative

equitability

“risk assessment, safety management, planned maintenance; all these

things have been brought in for big ships, but maybe the small ones have

slipped through under the wire …”

Monitoring “anything less than 12 pass and anything less than 24m [gets ignored]…”

Table 11: Evidence Category: Legislation

29

Tow Planning & Command: A lack of planning and the command of towage

operations were identified as risks to safety.


Planning “they’d planned the job up until [buoy x], but not for the rest of the pilotage

…”

Command “there were really two people in charge of the operation…”

Table 12: Evidence Category: Tow Planning & Command

Maintenance: A lack of maintenance (in particular of critical / safety equipment) was

identified.


Maintenance

Failures

“you’ve got the classic tow hook, not being maintained, it has been the

cause of many accidents …”

Table 13: Evidence Category: Maintenance

Design & Complexity: Advances in vessel design and increasing complexity were

seen as risk factors.


Design “assisted vessels, become ever bigger, faster, heavier, deeper, [with

operations] all at more speed …”

Complexity “… they’ve got so sophisticated nowadays, and it’s the engine that does you;

it stops, because some silly alarm goes off …”

Table 14: Evidence Category: Design & Complexity

Seamanship & Rope Management: Seamanship & Rope Management were

identified as risks factors.


Rope

Management

“… a man gets hand trapped in towing hawser …”

Table 15: Evidence Category: Seamanship & Rope Management

30

Crewing: Lack of sufficient crew of adequate professional training were

identified as risk factors.


3 Man

Crewing

“In big port entrances the lookout is left very much to other vessels ….”

Table 16: Evidence Category: Crewing

Communications: Poor communications were only explicitly raised by one expert,

although associated ‘communications’ factors were cited.

Stability: Lack of stability was identified as a high severity risk to safety; in

particular this concerned loss of watertight integrity resulting from insecure openings.


Watertight

Integrity

“tugs have got such bloody good stability that you can yank them right over

and they will bounce back. But they won’t bounce back if you’ve got a door

open ...”

“it’s always someone leaving the door open …”

Table 17: Evidence Category: Stability

Human Factors: Human Factors were cited as a risk to safety; but there were

contradicting statements advocating that the situation had improved.


Fatigue #1 “the crew were all seasick, and the master couldn’t physically do anymore

…”; versus:

Fatigue #2 “in the old days there was less control, you had to keep working …”

Table 18: Evidence Category: Fatigue

Training: The need for improved Training was cited as a risk factor. This

element related to other Risk Factors including: Following Operational Procedures, Tow

Planning, Tug Handling and Communications; additional linked codings’ included personal

qualities, and the importance of team working & judgement.

Code Sample statements

Training “a Voith Schneider captain is not an ASD tug captain and vice-versa …”

“lack of thought by [the assisted] vessel’s bridge team was a problem…”

Table 19: Evidence Category: Training

31

Personal Qualities & Negative Attitudes: Related to Training, the importance of Personal

Qualities & Judgement, were identified as safety factors.


Personal

Qualities &

Judgement,

“you need to be experienced enough to say yes I can do it, or no it’s too

risky - it’s a fine line…”

“it needs a certain personality able enough to cope with the wildness [power]

of this tug, in fact it must be an anti macho figure…”

Negative

attitudes

“one [problem] is complacency; old skippers saying, I’ve always done it this

way…”

“there is no reason for this to occur other than negligence …”

Table 20: Evidence Category: Personal Qualities & Negative Attitudes

Time: Lack of Time was identified as a threat to safety of operations; both internal

(e.g. as a human quality of rushing) and external (e.g. commercial pressure).

Code Sample statements

Internal “people, to gain time for whatever reason, end up in all sorts of risks…”

External “to be able to learn to drive safely, skippers need to be given time …”

Table 21: Evidence Category: Time

32

3.4 Comparison of Harbour Towage and Non Harbour

Towage Data

Harbour Towage (HT) operations had eighteen percent more Collisions, while Non Harbour

Towage (NHT) operations had thirty six percent more Groundings (See Graph 19).

Graph 19: HT to NHT Incident Category Comparison (relative frequency)

Harbour towage had at least twice the frequency in all Consequence categories (See Graph

20).

Graph 20: HT to NHT Comparison of Consequences

33.3

48.1

25.9

11.1 7.4

51.7

12.1

29.3

0

6.9

0

10

20

30

40

50

60

Collision Grounding Capize / Founder

Fire Other

Re

lati

ve F

req

ue

ncy

Event

Non Harbour Towage Harbour Towage

5

8 3

20

15

25

6

52

0

10

20

30

40

50

60

Loss of Life Injury Pollution Damage

Fre

qu

en

cy

Consequnce


33

Forty percent of NHT operations involved towing from Forward, compared to forty six

percent of HT (See Graph 21).

Graph 21: Comparison of HT and NHT Towage Position (relative frequency)

Comparison between HT and NHT incidents, indicated similar proportions of barges (fifty five

to fifty three percent); however there was noticeable variation in all other categories (See

Graph 22).

Graph 22: Comparison of Towed Vessel Type between HT and NHT Case Studies

40.7

0

7.4

40.8

11.1

46.5

12.1

25.9

13.8

1.7

0

5

10

15

20

25

30

35

40

45

50

Tow fwd To aft Push Other / unknown

Amidships

Re

lati

ve F

req

ue

rncy

Towing position


0 0

55.6

44.4

20.7 15.5

53.5

10.3

0

10

20

30

40

50

60

Tanker, Bulk Carrier etc.

Container, RoRo, General

Cargo, etc.

Barge Other

Pe

rce

nta

ge

Vessel Type Non Harbour Towage Harbour Towage

34

Fifty one percent of NHT Towed Vessels were Broad Bowed, compared to seventy four

percent of HT.

Graph 23: Comparison between HT and NHT Bow Form Distribution

Comparison between HT and NHT incidents, indicated similar proportions of Small Towed

Vessels (under ten thousand tonnes Deadweight): fifty and fifty one percent respectively;

however there was noticeable variation amongst all other categories (See Graph 24).

Graph 24: Comparison of Towed Vessel Size

0

51.9 48.2

15.5

74.1

10.4

0

20

40

60

80

Fine to Moderate

Broad Unspecified

Pe

rce

nta

ge

Bow Form Non Harbour Towage Harbour Towage

48.1 51.9

0 0 0

15.6

50

17.2 17.2

0

0

10

20

30

40

50

60

Unknown <10K t 10-50K t 51-160K t >160K t

Pe

rce

nta

ge

Vessel Deadweight Category Non Harbour Towage Harbour Towage

35

Graph 25: Case Study Comparison of HT and NHT Risk Factor Frequencies

Risk Factor comparison between harbour and non harbour towage produced several

findings (See Graph 25). Eleven Risk Factors were present only in harbour towage

operations (in rank frequency):

Tug Handling (fifty three percent);

Rope Management & Seamanship (thirty four percent);

Interaction (thirty two percent);

Girting (twenty five percent);

Current (twenty four percent);

Ship Securing Arrangements (seventeen percent);

Ship Size [towed] (seventeen percent);

Personal Protective Equipment (PPE) (thirteen percent);

Tug Type (thirteen percent);

Communications Equipment (eight percent);

General Purpose Manning (six percent).

0

0

11

.1

66

.7

0

0

0

3.7

0

0

0

7.4

11

.1

0

11

.1 7.4

0

29

.6

0

25

.9

74

.1

51

.9

77

.8

11

.1

11

.1

74

.1

51

.9

0

18

.5

32

.8 25

.9

75

.9

44

.8

53

.5

34

.5

6.9

27

.6

17

.2

0

13

.8

63

.8

5.2

24

.1

8.6

10

.4

17

.2

25

.9

8.6

43

.1

82

.8

56

.9

87

.9

10

.4

17

.2

41

.4

48

.3

13

.8

27

.6

0

10

20

30

40

50

60

70

80

90

100

Inte

ract

ion

Gir

tin

g

Tow

Pla

nn

ing

Pas

sage

Pla

nn

ing

Tug

Han

dlin

g

Ro

pe

/ Se

aman

ship

Gen

eral

Pu

rpo

se …

Spee

d

Ship

Siz

e

Ship

Po

wer

Tug

Typ

e

Man

ou

evri

ng

Spac

e

Swel

l

Cu

rren

t

Win

d

Vis

ibili

ty

Ship

Sec

uri

ng …

Tug

Equ

ipm

ent

Co

mm

un

icat

ion

…

Co

mm

un

icat

ion

s

Hu

man

Fac

tors

Trai

nin

g

Man

agem

ent

Syst

ems

Cre

w N

um

ber

s

Bri

dge

/ E

qu

ipm

ent …

Wat

chke

epin

g

Follo

win

g O

per

atio

nal

…

PP

E

Oth

er

Fre

qu

en

cy (

pe

rce

nta

ge)

Risk Factor


36

Three Risk Factors were noticeably more frequent in Harbour Towage Operations:

Tow Planning (seventy five percent);

Manoeuvring Space (sixty three percent);

Speed (twenty seven percent).

Six Risk Factors had prominent frequencies in HT (and NHT) operations (in rank average

frequency):

Management Systems (eighty two percent);

Human Factors (seventy eight percent);

Watchkeeping (fifty seven percent);

Passage Planning (fifty five percent);

Training (fifty four percent);

Following Operational Procedures (fifty percent);

In addition, the average total number of risk factors was greater for HT (nine) than for NHT

operations (five).

Graph 26: Comparison of HT and NHT Risk Factor Volumes

0

2

4

6

8

10

12

14

16

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

Nu

mb

er

of

app

licab

le R

isk

Fact

ors

(to

tal)

Case Study (averaged)

Harbour Towage Occurences Non Harbour Towage Occurences

37

3.5 Hypothesis Testing: Was there a measureable

difference between Harbour Towage and Non Harbour

Towage Operations (Chi Square test)

A Chi Square test comparing Harbour Towage (HT) and Non Harbour Towage (NHT) Risk

Factors rejected the Null Hypothesis in ten out of ten cases. (The test could not be

performed on other Risk Factors whose Estimated Values were below ten).

Risk Factor Alpha

value

(0.05)

X2

value

Is there a relationship between Risk Factor

and Harbour Towage Operation?

Tow Planning 3.84 38.397 Yes

Passage Planning 3.84 14.356 Yes

Tug Handling 3.84 31 Yes

Rope Management &

Seamanship

3.84 21.861 Yes

Manoeuvring Space 3.84 31.758 Yes

Tug Equipment

Maintenance

3.84 11.420 Yes

Communications 3.84 13.313 Yes

Training 3.84 11.470 Yes

Lookout / Watchkeeping 3.84 18.144 Yes

Following Operational

Procedures

3.84 11.387 Yes

Table 22: Chi Square Test values

The Chi Square test of Risk Factors indicates a detectable difference between harbour

towage and non harbour towage operations (See Table 22.).

38

3.6 Comparison of Quantitative Data

3.6.1 Comparison of Secondary with Primary Harbour Towage

Quantitative Data

The most frequent Event in both Case Studies (fifty eight percent) and Questionnaires

(eighty seven percent) was Collision.

Graph 27: Comparison of CS and QU Events

The most frequent Consequence in both CS (eighty nine percent) and QU (ninety three

percent) was Damage. Both surveys also had a noticeable Loss of Life frequency (thirty

seven percent).

Graph 28: Comparison of Consequence Frequency

58

.6

12

.1

29

.3

0

6.8

87

.5

37

.5

34

.8

0

3.1

73

.05

24

.8

32

.05

0

4.9

5

0

10

20

30

40

50

60

70

80

90

100

Collision Grounding Capize / Founder

Fire Other

Fre

qu

en

cy (

pe

rce

nta

ge)

Event

Case Study Questionnaire Average

25

.9

43

.1

10

.4

89

.7

50

68

.8

65

.6

93

.8

37

.95

55

.95

38

91

.75

0

10

20

30

40

50

60

70

80

90

100

Loss of Life Injury Pollution Damage

Fre

qu

en

cy (

pe

rce

nta

ge)

Consequence Case Study Questionnaire Average

39

Conventional Tugs were most frequent in CS (fifty one percent) whereas ASD Tugs were

most frequent in QU (fifty six percent).

Graph 29: Comparison of Tug Type

Moderately powered Tugs were most frequent in CS (forty six percent) whereas Medium

powered tugs were most frequent in QU (fifty nine percent).

Graph 30: Comparison of Tug Power

51

.7

6.9

6.9

34

.5

25

56

.3

15

.6

3.1

38

.35

31

.6

11

.25

18

.8

0

10

20

30

40

50

60

Conventional ASD VS Unspecified

Fre

qu

en

cy (

pe

rce

nta

ge)

Tug Type


46

.6

25

.9

34

.5 2

4.1

28

.1

59

.4

9.4

3.1

37

.35

42

.65

21

.95

13

.6

0

10

20

30

40

50

60

70

Moderate (<30t) Medium (31-65t) High (>65t) Unspecified

Fre

qu

en

cy (

pe

rce

nta

ge)

Tug Power


40

A Forward tow position was most frequent in CS, whereas an Aft tow position was most

common in QU (both forty six percent).

Graph 31: Comparison of Tow Position

Barges were the majority of towed vessels in the CS (fifty three percent) whereas they were

the least frequent Category in the QU (three percent).

Graph 32: Comparison of Towed Vessel Type

46

.6

12

.1

25

.9

0

15

.5

25

46

.9

0

3.1

25

35

.8 29

.5

12

.95

1.5

5

20

.25

0

5

10

15

20

25

30

35

40

45

50

Tow fwd To aft Push Amidships Other / unspecified

Fre

qu

en

cy (

pe

rce

nta

ge)

Tow position


20

.7

15

.5

53

.5

10

.4

25

37

.5

3.1

34

.4 22

.85

26

.5

28

.3

22

.4

0

10

20

30

40

50

60

Tanker / Bulk carrier

Container / RoRo / General

Cargo

Barge Other / unspecified

Fre

qu

en

cy (

pe

rce

nta

ge)

Towed Vessel Type


41

The most frequent Bow form in CS was Broad (seventy four percent) whereas a Fine bow

form was most common in QU (thirty four percent).

Graph 33: Towed Vessel Bow Form Comparison

The most frequent Towed Vessel category in the CS was Small (fifty percent) (See Table 8)

whereas the most frequent category in QU was Large (thirty one percent).

Graph 34: Towed Vessel Size Comparison

0

15

.5

74

.1

10

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34

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Fine Moderate Broad Unspecified

Fre

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Bow Form Case Study Questionnaire Average

50

17

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15

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<10K t 10-50K t 51-160K t >160K t Unspecified

Fre

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Towed Vessel Deadweight (tonnes)


42

The most frequent Risk Factors in both the Case Study and Questionnaire were (average):

Human Factors (seventy five percent);

Tow Planning (seventy three percent);

Manoeuvring Space (sixty nine percent);

Training (sixty two percent);

Tug Handling (fifty six percent).

Graph 35: Comparison of Questionnaire & Case Study Harbour Towage Risk Factors

Other notable Risk Factors in both surveys were (average):

Communications (forty one percent);

Interaction (thirty nine percent);

Tug Equipment / Maintenance (thirty six percent);

Girting (thirty three percent).

Ship Speed and to a lesser extent Size also had notable frequencies (See Graph 36);

however there was clear variation between the CS and QU data:

Ship Speed (average forty eight percent, with forty one percent variation);

Ship Size (average thirty two percent, with twenty seven percent variation).

32

.8 25

.9

75

.9

53

.4

27

.6

17

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.8

63

.8

5.2

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.1

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43

.1

82

.8

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.9 4

6.9

40

.6

71

.9

59

.4

68

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46

.9

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.9

31

.3

75

40

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28

.1

37

.5

9.4

40

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18

.8

40

.6

68

.8

68

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39

.85

33

.25

73

.9

56

.4 4

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.05

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69

.4

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26

.1

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9.8

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0

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80

90

Fre

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Risk Factor

Case Study Harbour Towage Data Questionnaire Harbour Towage Data Average Harbour Towage Data

43

With the exception of Visibility, the remaining Risk Factors were presents on average, in

over ten percent of events.

Graph 36: Rank Difference Case Study Versus Questionnaire

The largest rank movement resulting from the different frequencies between the two surveys

was Ship Power (eleven places); Current, Swell, Communications, Girting and Visibility also

experienced rank movements of between four and six places (See Graph 37.).

-8

-6

-4

-2

0

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6

8

10

12

Viz

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un

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44

3.6.2 Additional Risk Factors

Eight Risk Factors were identified in the Case Studies (CS) and the Expert Interviews (EI)

but were not included in the Questionnaire (QU); four of these had frequencies of over forty

percent (See Graph 38):

Safety Management Systems (eighty seven percent);

Following Operational Procedures (forty eight percent);

Passage Planning (forty four percent);

Watchkeeping (forty one percent).

Graph 37: Additional Risk Factors identified in Case Studies

Stability, Time, and Crew Qualities & Attitudes were identified in the Expert Interviews, but

were not explicitly identified in the Case Studies or Questionnaires.

44

.8 34

.5

6.9

87

.9

10

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17

.2

41

.4

48

.3

0 10 20 30 40 50 60 70 80 90

100

Fre

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Risk Factor

45

3.7 Risk Factors

3.7.1 Questionnaire Risk Factor Frequency

According to the Questionnaires (QU) the most frequently occurring risk factors, present in

over half of events (in rank order were):

Manoeuvring Space;

Tow Planning;

Speed;

Human Factors;

Training;

Tug Handling;

Graph 38: Comparison of Weighted and Un-weighted Questionnaire Risk Factors

15

13

23

19

22

15

15

10

24

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Safe

ty F

acto

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ncy

SafetyFactor

Unweighted Weighted (by perceived importance)

46

3.7.2 Questionnaire Risk Factor Weighting

Questionnaire Risk Factor significance weighted by perceived importance, reflected and

amplified Risk Factor frequency (See Graph 40.); the most notable amplification being for:

Speed (one hundred and thirty one percent);

Ship Power [towed] (one hundred and thirteen percent);

Communications Equipment (one hundred percent);

Interaction (ninety three percent);

Tug Handling (ninety four percent);

Graph 39: Risk Factor Percentage increase due to perceived importance

93

.3

53

.9

82

.6

94

.7

13

1.8

46

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11

3.3

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pe

rce

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ase

Risk Factor

47

3.7.3 Questionnaire Risk Factor alteration in ranking

This altered the Risk Factor ranking in ten cases; the most notable movement being for

Speed (increase of four positions) and Ship Size (decrease of three positions) (See Graph

41).

Graph 40: Risk Factor rank change due to perceived importance

3.7.4 Questionnaire Overall Risk Factor Ranking

According to the QU, the six highest ranked Risk Factors (weighted or un-weighted) were:

Speed;

Manoeuvring Space;

Tow Planning;

Training;

Tug Handling.

-4

-3

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-1

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1

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3

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Ran

k C

han

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Risk Factor

48

3.8 Relationship between Risk Factor and Consequence

Severity

3.8.1 Pearson’s r Significant Number Test

A Pearson’s r significant number test, of the relationship between individual Risk Factor and

Consequence Significance, identified a Medium relationship (r value greater of 0.3) for three

factors:

Speed;

Tug Type;

Tow Planning

The test showed a Small relationship(r value greater than 0.1) for a further ten Risk Factors,

with no relationship found in six cases (See Table 23).

Risk Factor Pearson’s Number Correlation

Interaction 0.175452 SMALL

Girting 0.06754 NONE

Tow Planning 0.30077 MEDIUM

Tug Handling 0.28599 SMALL

Speed 0.37426 MEDIUM

Ship Size 0.1764 SMALL

Ship Power 0.21717 SMALL

Tug Type 0.32135 MEDIUM

Manoeuvring Space 0.16393 SMALL

Swell -0.0125 NONE

Current -0.1247 SMALL

Wind 0.06615 NONE

Visibility -0.0281 NONE

Ship Securing Arrangements 0.12329 SMALL

Equipment / Maintenance 0.03599 NONE

Communication Equipment 0.09308 NONE

Communications 0.15399 SMALL

Human Factors 0.15536 SMALL

Training 0.17561 SMALL

Total Number of Risk Factors 0.27939 SMALL

Table 23: Pearson’s r Significant Number Values

49

3.8.2 Risk Factor frequency compared to event significance

The largest positive rank movement (fourteen positions) resulting from the Pearson’s r test

was for Tug Type, while the largest negative movements were for Equipment / Maintenance

(nine positions) and Manoeuvring Space (eight positions).

Tow Planning, Speed, and Tug Handling remained top four Risk Factors; while Manoeuvring

Space, Human Factors and Training, fell in importance (See Graph 42).

Graph 41: Risk Factor Rank Movement: Questionnaire Frequency Versus Pearson’s r

Number

-2

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ove

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Risk Factor

50

3.8.3 Relationship between Risk Factor Total Frequency and

Consequence Significance

A plot of consequence significance against Risk Factor total frequency indicated a small

correlation between the two qualities (See Graph 43.).

Graph 42: Risk Factor Frequency variation with Consequence Significance

A Pearson’s r test of correlation between Consequence Significance and Risk Factor total

frequency produced a value of 0.279, also indicating a Small relationship (value 0.1 to 0.3).

0

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1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

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Sign

ific

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(n

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be

r)

Questionnaires (Rank Ordered by Consequence)

Consequence Significance

Risk Factor Frequency

51

4.1 Suitability of Method

While the Case Study (CS) sample was limited to three states, the Questionnaire (QU)

provided a wider sample. In addition, although the Expert Interviews (EI) were limited to five,

convergence was observed, indicating a degree of saturation.

Use of a Judgement (rather than Random) sample of experts, with a total of one hundred

and ninety seven years relevant experience, helped extend understanding of issues;

additional written depositions and task observation, provided further validation.

Interpretative subjectivity concerns were managed by carefully following an objective

process; preconceptions were avoided by completing analysis of the interview data before

commencing other surveying.

As a qualitative analysis process, difficulties quantifying Grounded Theory data were

reduced by:

attaining saturation;

cataloguing code volume;

logging interviewee emphasis;

using follow-up to check specific points.

While the Questionnaire enabled collection of specific contemporary primary data, the issue

of authentication was managed by follow-up confirmation. Self-selection and normal

distribution problems, were reduced by use of non parametric tests.

The Qualitative and Quantitative processes had complementary aspects. The interviews

developed emergent theory and provided depth & granularity, but posed difficulties for

quantification; the surveys, using predetermined indicators enabled quantification, but risked

omitting symptoms (as demonstrated by the Questionnaire not including eight Risk Factors).

4.0 Discussion

52

Although interviews and surveys did not use identical codes, loss of comparative accuracy

was reduced by preserving generic categories so far as possible; use of three methods with

different data sources, also increased diversity. Triangulation, combining quantitative with

qualitative surveying, validated and deepened understanding of relationships between

variables.

This methodology helped identify and quantify Risk Factors in harbour towage operations,

enabling production of a baseline to help develop further analysis. A longitudinal

methodology might however improve evaluation of Risk Factor frequency against likelihood,

and help gauge success of any interventions.

53

4.2 Harbour Towage versus Non Harbour Towage

More frequent Collisions in harbour towage (HT) operations, compared with more frequent

Groundings in non harbour towage (NHT) operations, suggest the presence of differing

underlying Risk Factors; for example, Collisions might indicate Manoeuvring Space, while

Groundings might point towards Watchkeeping Risk Factors.

While harbour and non harbour towage had similar frequencies of towed Barges, harbour

towage also included a range of vessel categories. This difference may have been because

tugs involved in non harbour towage, had accidents where no other vessel was involved.

This non harbour towage characteristic was repeated, in high proportions of Unspecified

Bow Forms and Unknown Deadweights; and it compares with a broader cross section of

categories for harbour towage accidents. In this respect, harbour towage operations

accidents are more likely to involve another vessel.

With respect to Risk Factor variation, eleven factors were present in HT, but absent from

NHT operations; these Risk Factors may therefore be considered specific to HT operations.

A further five showed a more than twenty percent deviation; these Risk Factors may be more

common in HT operations.

Certain Risk Factors were present in over fifty percent of HT operations; their presence and

high frequency might be specific to these operations. By contrast other Risk Factors had

comparable or high frequencies in both groups, and might therefore be typical of all types of

operations. Others were comparatively more frequent in NHT, and may therefore not be

features of HT operations.

Only nine out of twenty eight Risk Factors had less than ten percent variation between NHT

and HT operations; they may therefore be present in similar frequencies in both types of

operation.

Comparatively higher total frequencies of Risk Factors in HT (See Graph 26) might indicate

volume of Risk Factors is a feature.

A Chi Square test of Risk Factor correlation between NHT and HT rejected the Null

Hypothesis in one hundred percent of cases; supporting the possibility that these two types

of operation can be differentiated.

54

4.3 Case Study versus Questionnaire Data

In both surveys, likelihood of Collision was twice the size of other categories (even with a

difference of twenty eight percent between them); by contrast there was a small difference in

likelihood of Damage.

There is a fifty five percent difference in the likelihood for Pollution between the surveys;

apart from this, categories retain similar proportions. A possible cause of this disparity is the

difference in type of Safety Event: Questionnaires comprised fifty five percent Near Misses

(where concern for pollution was perhaps higher than real risk, due to protective measures in

ship design).

Variation between survey data may also suggest two separate populations were studied;

over fifty percent of the QU concerned Medium powered ASD tugs, towing a range of vessel

types and Deadweights, involved in Near Misses. By contrast over fifty percent of CS

concerned Accidents to Moderately powered Conventional tugs, towing Barges of under ten

thousand tonnes deadweight. Weighting for Flag tug fleet size might however, allow a more

accurate evaluation.

While two different harbour towage populations may have been studied in the QU and CS,

similar Risk Factor profiles were observed. Although likelihood of Collision varied between

data sets, as a proportion of its cohort this difference was limited to eleven percent. Equally,

the largest difference was consequence of Pollution; however, as a proportion of their

respective cohorts, this amounted to a difference of seventeen percent.

The surveys identified thirty seven percent average frequency for Loss of Life, compared

with a fifty five percent average Injury frequency. There may be a number of reasons for this

including survey data sources only capturing substantial accidents.

Another potential source for the observed differences are disparities in the incident

categories. Ninety five percent of CS concerned Accidents, compared with nine percent of

QU: it is possible that this event seriousness may therefore have had an impact.

55

Differences in Vessel Type and Tow Position between data sets also require further

exploration. One possibility for observed variation is sample disparity; QU data was

collected from fourteen states, whereas two thirds of the CS were from North America,

where there is a well developed inland towage industry. Another potential explanation is

sample size; there were almost twice as many CS as QU.

Although, for eight Risk Factors, there was a difference of more than fifteen percent between

HT data sets, the majority more closely correlated; including the five most frequent Risk

Factors:

Tow planning;

Manoeuvring space;

Training;

Tug Handling;

Human factors.

Differences in frequency between the two HT surveys (& excluding NHT) led to an average

Risk Factor rank position movement of three places. The most profound Risk Factor

movement (Ship Power) was because it wasn’t included in the Case Study Data; however

the four most frequent Risk Factors remained the same in both surveys:

Human Factors;

Tow Planning;

Manoeuvring Space;

Training.

High frequency Risk Factors, identified in CS and EI, but not the QU, included:

Management Systems (eighty seven percent);

Following Operational Procedures (forty eight percent);

Passage Planning (forty four percent);

Watchkeeping (forty one percent);

The QU enabled a weighting to be added to individual Risk Factors to illustrate their effect in

an individual incident. While this amplified Risk Factor significance by different amounts

(and caused an average rank movement of one position) the six most significant Risk

Factors remained the same.

56

The largest rank change amplification and rank movement (four places) was for Speed. This

reflects the importance placed on Speed as a Risk Factor, by participants both in QU and EI.

This conclusion is supported by results from the Pearson’s r significant number test, which

produced the highest correlation (value 0.37426) between Risk Factor and Consequence

Significance, for Speed.

This test also supported the importance of Tow Planning and Tug Handling, and inflated the

significance of Tug Type; it however lowered the ranking of Manoeuvring Space, Human

Factors and Training. This may have been because these factors are more frequent and

therefore less important, to an individual accident.

A plot of Risk Factor volume against significance of incident, also indicated a relationship;

the higher the volume, the greater the accident significance. A Pearson’s r test value of

0.279 supported this (signifying a Small relationship between the two variables). This

feature should however be treated with caution, since individual Case Studies demonstrate

that one or two Risk Factors can be involved in some of the most catastrophic incidents;

while several Risk Factors can be implicated in lesser incidents:

Case study One: a tug pushing barges veered off course, ramming a pier and

collapsing a bridge, leading to multiple fatalities. The investigating safety agency

determined that the six risk factors were involved.

Case Study Two: a tug towing barges veered off course striking a dock and small

moored vessels. The investigating safety agency identified double the number of risk

factors, in an accident with fewer consequences.

57

4.4 Risk Factor Quantity

Since the data was not normally distributed, to test whether Safety Factor quantity had any

influence, a simple plot of accident severity against Safety Factor frequency showed some

increase, however there were:

significant fluctuations;

notable maximum Risk Factor frequencies in mid ranked incidents;

reductions in Risk Factor frequency for the most severe incidents.

A Pearson’s r test correlating Safety Factor total frequency with incident severity, produced a

value of 0.27939, signifying a Small relationship.

4.5 Risk Factor Severity

While analysis for presence of specific Risk Factors produced results in Graph 36, these

indicate volume of occurrence; they do not show the magnitude of their effect. For example,

while Safety Management Systems failure was observed in 87% of accidents, this Risk

Factor may have only played a small part as a cause; by contrast girting was only present in

17% of accidents investigated, but may have formed a more fundamental cause.

Therefore while Risk Factor frequency could provide an indication of its prevalence, this

does not indicate its significance in a particular event. The Pearson’s r test correlating Risk

Factor with perceived significance provided some indication of quality. For fifteen Risk

Factors this test and the frequency table, provided corresponding results; this may suggest

Risk Factor frequency also provides some indication of quality. There were two notable

exceptions, Manoeuvring Space was relegated to a ‘Small’ effect, while Tug Size was

increased to a ‘Medium’ effect.

58

4.6 Individual Risk Factor Explanation

Tow planning:

Was the next most frequent Risk Factor (seventy three percent). Although risks from

a lack of Tow Planning were not restricted to harbour towage, they were seven times

more frequent in these operations.

Manoeuvring Space:

One of five most frequent Risk Factors in the studies (sixty nine percent) it was not

specific to harbour towage, but eight times more frequent in these operations. The

Pearson’s r test correlation with consequence significance, gave it one of the largest

negative rankings.

Speed:

Although one of most frequently occurring risk factors, indentified in all three

surveys, and present in over half of events, it showed clear data variation. It was not

specific to harbour towage, but had a noticeably higher frequency during these

operations. Of all the Risk Factors, Pearson’s r test gave Speed the highest

correlation to consequence significance.

Human Factors:

Although one of the five most frequent Risk Factors in the studies, it was not specific

to harbour towage operations. While cited on seventy five percent of occasions,

there were mitigating statements indicating positive change. Human Factors may

have an elevated presence due to a particular need for tug crews to remain alert and

focussed. The Pearson’s r test showed a Small correlation with consequence

significance.

Safety Management Systems & Legislative Oversight:

Had the most significant frequency (eighty seven percent) but were not specific to

harbour towage operations. Expert Interviews coded this topic as one of the most

pressing in order to improve safety.

59

Training:

Also one of the most frequent Risk Factors in the studies, it was not specific to

harbour towage operations. The Pearson’s r test showed a correlation with

consequence significance. Training was cited on an average of sixty two percent of

occasions and had links with other Risk Factors such as Tug Handling, Crew Qualities

and Tow Planning and Communication.

Tug Handling:

One of the most frequent Risk Factors (fifty six percent) for harbour towage; the

Questionnaire weighting increased its importance by ninety four percent, while the

Pearson’s r test identified a correlation with consequence significance.

Following Operational Procedures:

Had a notable frequency (forty eight percent) but it was not specific to harbour

towage operations. Expert Interviews, reported that, “tugs have got such good

stability, but they won’t bounce back if you’ve got a door open”.

Rope Management & Seamanship:

Coded a signature Risk Factor for harbour towage operations (thirty four percent)

due to the frequency of working with ropes and the critical effects for safety of any

rope failure.

Interaction:

A Risk Factor for harbour towage operations (thirty nine percent) received a ninety

three percent weighting importance in Questionnaires; the Pearson’s r test signifying

a correlation with consequence significance.

Girting:

A signature Risk Factor for harbour towage operations (thirty three percent

frequency). The Pearson’s r test gave no indication of a correlation with

consequence significance; however Expert Interviews pointed out that it still

regularly occurs.

60

Tug Type:

Was a signature Risk Factor for harbour towage Operations (twenty two percent).

The Pearson’s r test identified Tug Type as one of three factors possessing a Medium

correlation with consequence significance.

Communications:

A notable Risk Factor in all three surveys (forty one percent) but not specific to

harbour towage; the Pearson’s r test showed a correlation with consequence

significance.

Tug Equipment / Maintenance:

Identified as a Risk Factor (thirty six percent) but not specific to harbour towage.

Linked with the significance of Safety Management Systems, Expert Interviews

emphasised that as a last line of defence, “tow hook Emergency Quick Release

mechanisms, not being maintained, have been the cause of many accidents”.

Communications Equipment:

Identified in thirteen percent of Harbour Towage operations, received a one hundred

percent ‘importance’ weighting increase in questionnaires.

Ship Securing Arrangements:

Specific to harbour towage operations (twenty eight percent); the Pearson’s r test

showed a Small correlation with consequence significance.

Ship Size:

A signature Risk Factor for harbour towage operations (thirty two percent); the

Pearson’s r test provided a Small correlation with consequence significance, however

there was clear variation within the data.

61

Ship Power:

Since it was not identified in the Case Studies this Risk Factor had a lower average

frequency (twenty three percent) giving a rank decrease of eleven places. It had a

Questionnaire ‘importance’ weighting increase of one hundred and thirteen percent

and the Pearson’s r test indicated a correlation with consequence significance.

Swell:

At twenty two percent this Risk Factor was not specific to harbour towage. The

Pearson’s r test gave no indication of a correlation with consequence significance,

although the Expert Interviews gave it increased weighting.

Current:

At twenty six percent, and as a signature Risk Factor to harbour towage operations,

the Pearson’s r test indicated a Small correlation with consequence significance.

Wind:

While not specific to harbour towage (twenty three percent frequency) Expert

Interviews increased its categorization.

Visibility:

Although at under ten percent frequency and not specific to harbour towage, Case

Studies did reveal a proportion of accidents occurred at night.

Crew Numbers:

Not specific to harbour towage operations (ten percent frequency) a number of crew

related risk factors concerning general purpose manning and appropriate

qualifications were identified by Expert Interviews.

62

Watchkeeping:

Had a frequency of forty one percent, but was not specific to harbour towage.

Passage Planning:

Had an average frequency of forty four percent, but was twenty two percent greater

in non harbour towage operations.

Bridge / Equipment Design:

It was not identified as specific to harbour towage (seventeen percent); Expert

Interviews however commented that new vessels can have dead slow speeds in

excess of ten knots, posing problems for securing tugs.

PPE:

Had a frequency of thirteen percent in harbour towage operations.

Other Risk Factors:

A range of other factors were reported including, working while intoxicated, and

poor tow marking.

63

5.1 Suitability of method

The methodology employed demonstrated a degree of success identifying and quantifying

Risk Factors in harbour towage operations. Triangulation, combining quantitative with

qualitative surveying, and contrasting emergent with established concepts, helped validate

and extend understanding of underlying relationships between the different variables.

The research enabled production of a baseline for further analysis; however greater use of

longitudinal sampling might improve identification of any relationship between Risk Factor

frequency and event likelihood, and help to measure success of any intervention.

5.0 Conclusions

64

5.2 Analysis of Risks to Safety

The results indicated that the Risk Factors involved in harbour towage operations could be

distinguished from those existing in other maritime sectors; however they also revealed that

the relationship between variables was complex, and that development of any solutions may

require considerable thought.

The Chi Square Test comparing harbour with non harbour towage operations rejected the

null hypothesis, indicating that the two sectors could be differentiated.

Analysis of the two sectors recognised the existence of different Risk Factors, and in

different proportions. Eleven Risk Factors were present only in harbour towage operations,

with a further three noticeably more frequent. Additionally, the average number of risk

factors was greater for harbour towage (nine) that for non harbour towage operations (five).

Particular Risk Factors specific to or with elevated frequencies during, harbour towage

operations, included:

Tow Planning (seventy five percent);

Manoeuvring Space (sixty three percent);

Tug Handling (fifty three percent);

Rope Management & Seamanship (thirty four percent);

Interaction (thirty two percent);

Speed (twenty seven percent).

Girting (twenty five percent);

Current (twenty four percent);

Risk Factors with significant frequencies (but not specific to harbour towage) included:

Management Systems (eighty two percent);

Human Factors (seventy eight percent);

Watchkeeping (fifty seven percent);

Passage Planning (fifty five percent);

Training (fifty four percent);

Following Operational Procedures (fifty percent).

Weighting of Risk Factor with significance of effect altered rank position, however the most

frequent Risk Factors remained the same.

65

A Pearson’s r test correlating Risk Factor with consequence significance, also altered rank

position, elevating relative importance of Tug Type, Ship Size & Power and Interaction.

A plot of Risk Factor frequency against consequence significance, indicated a potential

relationship, and a correlation test endorsed this.

Key Harbour Towage operations Risk Factors, identified by frequency or significance

1 Safety Management Systems (eighty two percent);

2 Tow Planning (seventy five percent);

3 Manoeuvring Space (sixty three percent);

4 Speed (twenty seven percent).

5 Human Factors (seventy eight percent);

6 Training (fifty four percent);

7 Tug Handling (fifty three percent);

8 Following Operational Procedures (fifty percent).

9 Rope Management & Seamanship (thirty four percent);

10 Interaction (thirty two percent);

11 Girting (twenty five percent);

12 Tug Type (twenty two percent);

13 Communications (forty one percent);

14 Tug Equipment & Maintenance (thirty six percent).

Table 24: Key Harbour Towage Risk Factors

Evidence of a correlation between Risk Factor frequency and consequence significance

should be balanced with the complexity of relationships between variables (and evidence

that a small number of Risk Factors can underlie the most catastrophic of accidents).

The most likely harbour towage operations safety event is Collision (seventy three percent)

followed by Capsize / Foundering (thirty two percent) and Grounding (twenty four percent).

The most likely consequence is Damage (ninety one percent) followed by Injury (sixty five

percent) and Pollution (thirty eight percent). There is also evidence of a prominent risk of

Loss of Life (thirty seven percent).

Variation between Case Study and Questionnaire data suggest two separate populations

may have been sampled (although no weighting for Flag State tug fleet size was used).

66

Over fifty percent of the Questionnaires concerned Medium powered ASD tugs, towing a

range of Vessel Types and Deadweights, involved in Near Misses. By contrast over fifty

percent of Case Studies concerned Accidents to Moderately powered Conventional tugs,

towing Barges of under ten thousand tonnes Deadweight.

Areas identified by the surveys that might benefit from further analysis include, provision of

an equitable system of regulatory oversight for the benefit of all tugs. A disproportionately

high number of smaller uninspected tugs, involved in accidents, provided limited anecdotal

evidence to support this. More substantial Risk Factor evidence includes the relative high

frequency of inadequate Safety Management Systems and Human Factors (legislated for in

International Maritime Conventions).

Changes to vessel design and increased complexity were identified as factors. Expert

Interviews reported that modern engine management systems can provide dead slow

speeds of ten knots; equally tug power has increased to an extent where bollard strength

can be insufficient.

The importance of an adequate number of appropriately qualified and experienced crew

were also recognised. A traditional method of training tug crews from deck boy to skipper, is

sometimes being replaced by migration from other maritime sectors; these new entrants may

not be similarly aware of Risk Factors specific to harbour towage operations.

Training issues underlay several Risk Factors: Tow Planning highlighted the importance of

the provision of sufficient information and experience to those managing harbour towage

operations; Following Operation Procedures underlined the importance of effective tug crew

drill programmes; and Tug Handling emphasised the importance of adequately preparing tug

masters.

Expert interviewees indicated that Training matters might also extended to personal qualities

and attitudes; pointing out the importance of teamwork and effective communication in safe

harbour towage operations. One particular code, Judgement (the ability to make a decision

concerning whether an action was safe) was highlighted; whether this was with respect to

handling a new generation of tugs (with reported exceptional tug size to power ratios) or the

ability to decide if a vessel’s speed was safe to close on her bow to make a tow.

67

6.1 Harbour towage operations reporting and research

This may help to monitor risks to safety and assist in developing solutions.

6.2 Equitable Regulatory Oversight and Monitoring

This may help provide an equitable system of regulatory oversight and monitoring, allowing

relevant International Conventions to benefit more tugs, while ensuring adequate Safety

Management Systems are in place.

A: Tug Masters and Crew: participate in confidential hazardous event

reporting.

B: Maritime Academic Institutions: undertake a comprehensive

detailed study of harbour towage operations safety risk.

A: Regulators: Review the current five hundred Gross Tonne threshold

in relevant International Conventions.

6.0 Recommendations

68

6.3 Enhanced Training Provision

Enhanced training provision may enable better planning and management of harbour tow

operations; common tug handling standards may help to build best practice; and, enhanced

harbour towage operation emergency drills may help to improve safety, for all those involved

in this crucial maritime sector.

A: Harbour Masters and Maritime Pilots Associations’: Consider

opportunities for improving harbour towage operations planning and

management.

B: Regulators and tug organisations: Consider development of common

standards of training in Tug Handling.

C: Regulators and tug organisations: Consider delivery of standard tug

harbour towage operations emergency drills.

69

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A

Appendix A.

A-1 Example Tug Towage Safety Questionnaire

This questionnaire has been produced by Stephen Ford, a serving tugmaster, as

part of a research project into Tug Safety, with Solent University. The purpose of

this questionnaire is to identify the specific risks involved in harbour towage

operations.

It is addressed to all tug masters and asks them to describe one tug towage job

which raised a safety issue. This might have been a near miss or an incident, but it

includes challenging jobs; for example where you did things differently the next

time.

All information provided will remain strictly confidential to myself, the researcher.

Anything that attributes information to a particular person, vessel or company will

be removed: any information provided is purely for statistical analysis. All

responses will be destroyed upon completion of the research project in June 2013.

To fill in the form, tug masters are asked to put a cross (X) in the most applicable

box. If a question is not applicable, you are unsure about the answer, or you do

not wish to answer a question, please leave it blank.

Please email your completed questionnaire by 10/04/2013 to:

[email protected]

For more information about the project and for the results of the research

(available June 2013) please go to:


Alternatively I can be contacted at the above email address.

Thank you for your help with this research.


B

Details of the tug towage job which raised a safety issue

The Tug 1. Type of tug Conventional

(propeller/ rudder)

ASD Tractor Not known / other

………

2. Tug Bollard Pull approximate (tonnes)

Moderate <30t

Medium 31t - 65t

High > 66t

Not known / other

The Assisted Vessel 3. Assisted vessel type (Container, barge, etc.)

(Please state) … …………………………………………………..

4. Approximate size (deadweight, tonnes)

Barge or Coaster (<10,000t)

Handy (10,000-50,000t)

Large (51,000-160,000)

Very Large (>160,000)

Not known / other

5. Bow form Fine Moderate Broad Unsure / other (Please state)

……

Tug Assistance Provided 6. Tug Help Push &/or pull Tow on a

line Not known / other

(Please state)

………

7. Tug Position

Tug Forward Amidships Tug Aft Not known / other (Please state)

………

8. Whose line

Tug’s Ship’s Unsure / Not Appropriate

External factors

Conditions / Weather 9. Wind (Beaufort Scale)

Low <F3

Moderate F4-F6

Gale F7-F83

Storm >F9

Unsure

10. Swell height (m)

Calm <0.2

Moderate 0.3 – 0.9

Rough 1.0-1.5

Storm >1.5

Unsure

11. Current (knots)

Low <1

Moderate 2-3

Strong >3

Unsure

12. Other external condition (please state)

……………………………

C

The Safety Issue

The risk 13. How likely were the following outcomes in this case

Not likely / Not applicable

Possible Likely Highly likely Inevitable

a. Collision

b. Grounding

c. Foundering

d. Major damage

e. Minor damage

f. Loss of life

g. Major Injury

h. Minor injury

i. Pollution

The event 14. How would you best describe the event:

Challenging / Instructive

Near miss Incident Accident Other

Brief description 15. Please use this space to briefly describe any other factors not already covered elsewhere.

D

Thank you for completing this questionnaire; please email it to: [email protected]

Extent to which different factors were involved

Factors involved 16. Indicate the extent to which the following factors influenced the safety issue.

Factor No effect / Not Applicable

Some effect Important effect

Fundamental effect

Interaction between tug & tow (e.g. tug enters bow pressure wave)

Girting, Girding or Tripping (e.g. gobbing down gear absent or inadequate)

Insufficient detailed planning of tow (e.g. insufficient tug bollard pull ordered)

Ship speed too fast (e.g. tug unable to maintain required position)

Ship size too large for tug/s (e.g. windage too great for tug bollard pull)

Ship too powerful for tug/s (e.g. main engines overpowering tug pull)

Wrong tug type used for job (e.g. conventional tug used in vulnerable position)

Lack of manoeuvring space (e.g. restricted by shallow water, buoys or piers)

Excessive swell (i.e. snatching or parting tow line)

Excessive current (e.g. difficult to control tow)

Excessive wind effect (e.g. too great for tug power)

Practical difficulties (e.g. need to remain in ‘critical area’ to pass tow line)

Poor ship securing arrangements (e.g. poor fairleads or bollards)

Tug equipment (e.g. failure of emergency quick release)

Inadequate communication equipment (e.g. poor VHF)

Language difficulties (e.g. lack of spoken English)

Human factors (e.g. poor concentration, fatigue, etc.)

Training insufficient (e.g. not enough time on new tug type)

Other (please state) ………………………..

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