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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