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Forensic Engineering ServicesSlips, Trips and Missteps
Presented to the Society of Public Insurance Administrators of Ontario
September 30, 2011
Richard Nellis - Qualifications• Over 25 years of engineering experience and
service to the insurance and legal professions• Vice President and Manager of Forensic and
Environmental Services• Completed over 400 fall accident
assessments since 2000, including slips, trips, and stair falls, for insurance and legal clients
• Certified XL Tribometrist• CFEI - Fire & Explosion Investigator• Completed over 350 fire investigations and
over 250 environmental site assessments
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Company Profile• Established 1961
– 50 years of Engineering Services• Consulting Engineering Services for:
– Building Owners– Property Managers– Land Developers– Insurers
• Qualified Staff – P.Engs, CETs, CFEIs
• Wide Variety of Specialties:– Building Science– Project Management– Structural Engineering– Mechanical/Electrical Engineering– Environmental Engineering– Forensic Engineering & Litigation Support
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Forensic Engineering and Litigation Support
• Slips, Trips, Missteps• Stair Falls • Fire Investigation• Failure Analysis• Structural Collapse Assessment• Design Review• Construction Review• Expert Witnessing, Plaintiff and Defence• Code & Regulation Compliance• Automotive Accident Reconstruction
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Presentation Objectives
• Services we offer• Kleinfeldt Methodology• Slips, Trips, and Missteps• Stair Falls• Drainage Assessments• Codes, Standards, and Best Practices• Case Studies
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Kleinfeldt Methodology
Scientific Method• Industry recognized
procedure• Defines scope• Focuses the research• Defends the work• Supportable conclusions• NFPA 921
Recognize the need (identify the problem)
Define the problem
Collect data
Analyze the data(inductive reasoning)
Develop an hypothesis
Test the hypothesis(deductive reasoning)
Select final hypothesis
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Kleinfeldt MethodologyOrigin of Failure• Design: Decision based failure• Construction: Workmanship
based failure• Maintenance: Deterioration
based failure• Failure category overlap, e.g.
spalling bricks
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Applying Kleinfeldt Methodology
Goal: To determine a cause that is most consistent with all aspects of reported and gathered information– Slips, Trips, Missteps – Stair Falls– Drainage Failures– Building Code Assessments
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Slips vs. Trips vs. MisstepsTypical Slip Characteristics• Feet slide forward• Falls backward, landing on
back, side• Lubricant/contaminant on
the floor or the shoe• e.g. snow/ice on sidewalk
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Slips vs. Trips vs. MisstepsTypical Trip Characteristics• Foot caught or held back• Falls forward, landing on
hands, knees, face• Trip hazard present• e.g. crack in sidewalk
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Slips vs. Trips vs. MisstepsTypical Misstep Characteristics• Inaccurate foot placement• Fall in direction of momentum• Visual obstruction, unexpected
change in elevation• e.g. lack of demarcation on a
stair edge
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Stair Falls
Stair Fall Characteristics• Slip, trip, or misstep in origin• Many possible fall scenarios• Many possible contributing
factors
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Drainage• Liability claims increasingly more common– Uncontrolled drainage becomes a slip hazard in
the winter– Drainage disputes between neighbours– Flooding caused by improperly graded areas– Surface flooding caused by storm sewer systems
that are under-designed, poorly constructed, or poorly maintained
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Codes, Standards, Best PracticesBuilding Codes• In effect: in place at the time of construction or
renovation
Property Standard By-Laws• Applies to all areas of a property
O.Reg 239/02: Minimum Maintenance Standards for Municipal Highways
• Defines a surface discontinuity on a municipal sidewalk: 2 cm [O. Reg. 23/10, s. 10.]
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Codes, Standards, Best PracticesCAN/CSA-B651-04: Accessible Design for the Built
EnvironmentASTM F-1637: Standard Practice for Safe Walking
Surfaces“The Staircase, Study of Hazards, Falls, and Safer
Designs,” John Templer“The Application of Forensic Biomechanics to the
Resolution of Unwitnessed Falling Accidents,” Journal of Forensic Sciences, Alex Sacher
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Case Study: Slip, Trip, or Misstep?• A woman fell as she was
descending the final stair leading to the newly constructed municipal sidewalk
• She fell forward, with her head landing on the boulevard
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Case Study: Slip, Trip, or Misstep?
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Case Study: Slip, Trip, or Misstep?Reported Information•“Slipped” on sand and leaves•Landed with head toward the boulevard and feet near the driveway•Broken ankle
Biomechanics Analysis• Slip: causes a backward fall• Trip: causes a forward fall, broken ankle unlikely• Misstep: generally causes a forward fall, broken ankle
possible
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Driveway
Sand and Leaves
Boulevard
Case Study: Slip, Trip, or Misstep?Plaintiff Expert Report• Slippery conditions caused by
sand on the interlocking pavers• Slip testing conducted off site
on a masonry brick, concluding sand on brick was slippery
Analysis• The slippery condition was not the cause of
the fall– The fall was a misstep, not a slip
• Irrelevant testing of inappropriate materials
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Case Study: Slip, Trip, or Misstep?Plaintiff Expert Report• Distance from riser to
sand/debris area (16”) is typical for a single step in descent
Analysis• The woman reported stepping on the
edge of the sidewalk, which was 24” from the riser– Much longer than a typical step in
descent
• Typically, people step down with the ball of the foot– Unlikely to slip as momentum is
mostly vertical with this foot position
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24”
16”
Case Study: Slip, Trip, or Misstep?
KCL Opinion: Misstep• Slip unlikely due to landing position and injuries • Trip unlikely due to biomechanics and injuries• A misstep is most consistent with the reported information,
final position, injuries, and physical attributes of the landing– “Air step”: where the person thinks they are already at the bottom,
and steps forward – Foot placed on pebble or other object causing her to roll her ankle
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Case Study: Slip on Ice• A man was walking on
his driveway and slipped on ice
• The ice extended across the width of the driveway
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Case Study: Slip on Ice
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Case Study: Slip on IceSlip Assessment• Why did the slip
occur?• Codes and
Standards
Case Study• Ice, due to uncontrolled
drainage, on the driveway– “As Constructed” drawings revealed
that a catch basin was missing after a recent construction
• Municipal Works Design Manual– Best practices– Basic design guidelines and
reference material
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Case Study: Slip on Ice
KCL Opinion: Failure of Construction• The new design required a catch
basin, which was covered during construction
• The ice was caused by uncontrolled drainage
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Case Study: Fall at a Threshold• A woman did not see
the step at the threshold of the building and fell as she was exiting
• It was night and the woman reported she could not see
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Case Study: Fall at a Threshold
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Case Study: Fall at a ThresholdPlaintiff Expert Report• Measured illumination
level• Step at threshold was a
“misstepping hazard”• No demarcation
Analysis• Illumination readings irrelevant
– Different time of year, atmospheric conditions, moon phases
• Reported lighting information was conflicting• Steps at exterior thresholds are somewhat
expected and the subject step could be seen through the glass door
• A metal threshold at the leading edge of the stair demarcated the step
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Case Study: Fall at a Threshold
Building Code and Building Permit Review• Code compliant• The step was identified in the drawings submitted for
building permit application• Approved by the municipality as being code compliant• Constructed in accordance with approved drawings• Owners were reasonable in their actions
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Case Study: Fall at a Threshold
KCL Opinion: User Behaviour • Appropriately designed• Code compliant• Light sources available• Step at threshold is expected and could be seen
through the glass door• Stairs were safe for persons taking due care for their
own safety
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Case Study: Stair Fall• A woman tripped at the
upper landing of the exterior concrete stairs leading to her basement apartment
• Catastrophic injuries, including paralysis
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Case Study: Stair Fall
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Case Study: Stair Fall
Stair Fall Assessment• Why did the fall
occur?• Codes and
Standards
Case Study• Trip hazard: raised lip at top
landing• Ontario Building Code• Property Standard By-law
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Case Study: Stair Fall
KCL Opinion: Construction Defect• The lip at the top of the stair was a trip hazard and
should not have been there• Not code compliant• Building Permit Search revealed “open” building
permit
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Other Areas of Service
• Risk Assessment• Construction Defects• Fire Investigations• Environmental Site Assessments
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