1 REVIEW OF PERTH’S TRANSPORT MODELS Introduction This brochure, prepared by the Department for Planning and Infrastructure (DPI) on behalf of the Western Australian Planning Commission (WAPC), provides information on Perth’s transport models and presents the findings of a recent independent review of the models. This brochure should be read in conjunction with the DPI/WAPC brochure Transport Modelling – General Principles (April 2005) that provides general information on transport modelling. APRIL 2005 Information Brochure
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REVIEW OF PERTH’STRANSPORT MODELS
IntroductionThis brochure, prepared by the Department for Planning andInfrastructure (DPI) on behalf of the Western Australian PlanningCommission (WAPC), provides information on Perth’s transport modelsand presents the findings of a recent independent review of the models.
This brochure should be read in conjunction with the DPI/WAPCbrochure Transport Modelling – General Principles (April 2005) thatprovides general information on transport modelling.
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Information Brochure
Perth’s transport modelsThere are three main transport models currently in use in Perth;
• DPI’s strategic transport evaluation model (STEM)
• Main Roads Western Australia’s (MRWA) regional operations model (ROM)
• The City of Perth’s detailed city centre operational model (CPM)
STEM is a high level (low resolution) “strategic” multi-modal model for landuse and transport policy assessment.
• It has around 500 zones and a road network consisting of all major roads and some of the more significant local roads. The boundaries of the zones coincide with the boundaries of zones in ROM.
• It is suitable for broad-brush studies of different transport and land use scenarios and transport policy options.
• The outputs of the model are flows of vehicles and travellers at the cordon or screenline level.
• It measures the performance of the metropolitan transport system in terms of economic efficiency, social impact and broad environmental impact.
ROM is a medium level “strategic/operational” road based model forassessing the impacts of road infrastructure projects and area-wide trafficmanagement measures.
• It has over 1,000 zones and a finer road network than STEM consisting of all major roads and many local roads.
• It is suitable for studies of the road traffic impacts of road infrastructure projects.
• It provides traffic volume data for use in the planning and design of elements of the road traffic system, such as interchanges and intersections.
• It may also be used to study regional traffic impacts of land use development projects.
• The model estimates vehicle flows at the network link (ie individual section of road) level.
• It measures the metropolitan road network performance in terms of economic efficiency.
• Its outputs may also be used for studies of social and environmental impact.
CPM is a detailed level (high resolution) “dense operational” road basedmodel for assessing the local traffic impacts of alternative trafficmanagement plans and individual land use developments in the Perthcentral business district (CBD).
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• It has nearly 200 zones representing city blocks and major car parks. Its road network consists of all roads in the city centre and includes detailed intersection layouts.
• It is suitable for studies of traffic management schemes for the CBD, including traffic signal settings and signal coordination plans, turn bans, access restrictions and one-way street systems.
• It can analyse the traffic impacts of the car parking system and of individual land use developments in the CBD.
• The model outputs detailed traffic flows, including turning movement flows, travel times and delays, and traffic system performance measuressuch as degrees of saturation at intersections.
Background to reviewThe main catalyst for the review was criticism of the MRWA model by anumber of individuals and organisations that disagreed with some of theroad planning decisions made based on, or supported by, traffic flow datafrom the model.
The review was undertaken by Professor Mike Taylor from the TransportSystems Centre, University of South Australia. Professor Taylor is arenowned expert in transport modelling and had just completed a similarreview of the Adelaide transport models for the South Australian Departmentof Transport and Urban Planning.
Review processThe review was coordinated by DPI under the direction of a steering groupmade up of officers of MRWA, DPI and City of Perth.
The scope of the review was expanded beyond the initial request for areview of the ROM model to include a review of the STEM and CPM modelsand to provide recommendations on the future direction of transportmodelling in Perth.
The review was undertaken in three stages as follows.
Stage 1 – detailed review of the ROM model
Stage 2 – comparison of ROM with the STEM and CPM models
Stage 3 – recommendations on the future direction of transport modelling in Perth
The review commenced in February 2003 and was completed in April 2004.
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Review objectivesThe main objectives of the review were to:
• establish the transport modelling requirements for the Perth metropolitan area;
• identify the purposes and uses for which the existing models have been developed (and any limitations on their use);
• determine whether the models satisfactorily meet these purposes and uses, and those of their key stakeholders and users;
• provide a comparative assessment of the three models with respect to strengths, uses and limitations;
• assess whether any or all of the criticisms directed at the MRWAmodel were justified and if so, what changes could be made to rectify the deficiencies in the model;
• identify any other areas where the models could be improved; and
• establish a strategy to best satisfy Perth's future transport modelling needs.
Stage 1 – Review of ROM model
Process
The review commenced with consultation with a wide range of stakeholdersincluding key critics of the model, transport and planning officers in MRWA,DPI and City of Perth and transport and planning consultants.
A detailed technical review of the model was then undertaken including theappropriateness and validity of the input data, the calibration of the model,its valid uses and its limitations.
Key criticisms
Listed below are the key criticisms directed at the model.
1. The model did not take into consideration the targets for public transport and cycle usage set by the 1995 Metropolitan Transport Strategy (MTS)
2. The model used inconsistent and/or inaccurate land use and other demographic data.
3. The model was based on 1976 travel survey data that are outdated and unsuitable for predicting future travel patterns.
Key findings
The review found that these criticisms had some validity in the past but thatthe MRWA modelling group had responded positively to them. Significant
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improvements have been made in recent years addressing these and otherearlier limitations of the model.
In particular the review findings were:
1. ROM now employs the modal split percentages generated by STEM. Thus the demand for road-based transport modelled by ROM explicitlyuses the most recent modal split estimates, which include enhanced bus services and the new southern suburbs railway line;
2. ROM now takes the ‘business as usual’ land use scenario defined by STEM as its base. Population forecasts and other demographic projections used as input to ROM are those supplied by DPI; and
3. ROM still uses travel behaviour parameters derived from the 1976 travel survey, and then verified in the 1986 survey. This situation will change as soon as data from the current Perth and Regions Travel Survey (PARTS) are available and new parameters can be determined.
The overall conclusion was that:
While there is always room for improvement, especially as newdata become available, the model can be regarded as providinga valid representation of metropolitan road travel.
Professor Taylor also concluded that there is a general lack of understandingof transport modelling both within the relevant professions and thecommunity in general. This can lead to a misinterpretation or misuse ofmodel output and should be addressed.
This is occurring through the WAPC brochure on transport modelling anduniversity courses being introduced by the universities through the Planningand Transport Research Centre ( www.patrec.murdoch.edu.au). A modellingliasion group has also been set up to improve expertise within the profession.
Areas for further improvements
The review identified the following areas for development of the model in thefuture.
1. Development of a new traffic assignment module as a replacement for the existing module to include:
• time of day modelling (eg peak hours versus off–peak hours);
• improved route choice modelling;
• improved commercial vehicle modelling;
• improved public transport modelling; and
• bicycle modelling.
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2. Provision for modelling elastic travel demands, (ie modelling changes to the total number of trips on the network in response to changing traffic conditions on the network or transport policy) including:
• the spreading of the peak period due to congestion;
• induced traffic (eg widening a road can encourage more vehicles to use it);
• suppressed traffic ( drivers who would like to travel but don’t because of congestion); and
• the impact of congestion charging or increasing fuel prices.
3. Improved transparency and understanding of the model within the professional and general community including:
• what data have been input;
• what assumptions have been made;
• how it does what it does; and
• how to interpret the output.
Stage 2 – Comparison of ROM with the STEM model andthe CPM model
Process
Stage 2 involved a comparative assessment of the ROM model with theDPI’s STEM model and the City of Perth’s model. The assessmentconsidered the uses, strengths and limitations of each model and the levelof compatibility and interaction between the models.
Key findings
The key findings included:
• each model is an important tool for transport/land use planning and analysis;
• each has a unique area of application whilst being complementary (see the section on Perth’s transport models for details); and
• the three models currently provide a valuable combined analytical capability.
Areas for further improvements
The review identified the following areas for development of the modelsin the future.
• Recalibration of both ROM and STEM should be undertaken when the results of the Perth and Regions Travel Survey (PARTS) become
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available (This is scheduled in both the ROM and STEM development programs).
• There are opportunities for further data/output sharing between the models and these should be investigated.
• Enhanced and expanded freight and commercial vehicle modelling capabilities are required for both ROM and STEM.
Stage 3 – Recommendations on future direction oftransport modelling
Process
This stage initially involved consultation with key stakeholders, end usersand clients of the models to determine their short, medium and longer termmodelling requirements. The current modelling process was then assessedto determine whether it would satisfy these requirements and a futuretransport modelling strategy developed.
Key recommendations
• The ROM & STEM models perform differing and complementary functions and each has an important role in the planning and design of an integrated land use/transport system.
• Development of and support for both the ROM and STEM models should continue.
• ROM should continue to be based in MRWA, with adequate resources (eg 4 or 5 staff) provided by the agency for the support and developmentof this model.
• Relocation of STEM to the strategic infrastructure section of DPI should be considered (as this is closest to its growing user base), with adequate resources (eg 4 staff) provided to ensure the ongoing viability of the model and its enhanced uses within DPI/WAPC.
• A formal modelling liaison group should be established, including representatives of the modelling groups in MRWA, DPI, PATREC and City of Perth, and possibly other stakeholders, to promote model compatibility and coordinate information dissemination and future model developments.
• A freight transport modelling capability should be developed for metropolitan Perth, supported by data surveys to collect high-quality information about freight flows and commercial vehicle movements in the metropolitan area. This modelling capability should be available for use in both ROM and STEM.
• PATREC’s role in transport modelling in Perth should focus on research and model development and the development of an ongoing expertise inmodel theory and applications that will be available to the portfolio.
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• All production modelling work using STEM, ROM and other models in the portfolio should continue to be done within DPI and MRWA as appropriate, to best meet the needs of the users of model outputs.
• Areas for further development include traffic micro-simulation modelling and the use of the models to evaluate environmental impacts such as airpollution and noise.
Overall conclusionsThe overall conclusion of the review was that the three models are valuabletools for transport/land use planning, performing complementary rather thanoverlapping functions. They require continued and further development andneed to be adequately resourced to ensure that this occurs. There are alsoopportunities for greater consistency and interaction between the modelsand these should be pursued.
A second conclusion was that there is a lack of understanding of transportmodelling in general and of the Perth transport models within both therelevant professions and the general public and that this needs to beaddressed.
Review reportsThe reports from Professor Mike Taylor’s review are available on the WAPCwebsite under Publications at www.wapc.wa.gov.au.
UpdateBased on the review recommendations, an in-house transport modellingteam has been set up within the new Spatial Information and Researchprogram area of DPI, as part of the 2004/05 restructure.
The key function of the modelling team is to manage the STEM model onbehalf of the Department and the portfolio. Further information on STEMand the Department’s modelling capabilities can be obtained from DPI(phone 9264 7777) or from:
Erwin Swasbrook [email protected] Program leaderSpatial Information and Research
