pedestrian safety at intersections assessment of the walking security index - wsi safety and traffic...

Pedestrian Safety At Intersections

Assessment of the Walking Security Index - WSI

Safety and Traffic Services – 5 February 2003

5 Feb 2003 Safety & Traffic Services

Presentation Overview

• Background• Purposes of WSI• WSI Formulations• WSI Report – July 1998• WSI Refinements• Staff Concerns• Technical Review• Vulnerable Road Users


Background

• Spawned by public concern for pedestrian safety at right-turn cut-off ramps at signalized intersections• At most of these intersections few, if any, collisions involving pedestrians had been reported; nonetheless, complaints persisted in response to “close calls”• Resulted in “A Survey of Pedestrian Concerns and Attitudes at Right-turn Cut-offs” at Laurier/Nicholas by Professor Barry Wellar and his students as a class project in 1994-95• Results were inconclusive


Background

• WSI concept was formulated by Professor Wellar and evolved as a “spin off” project from the Laurier / Nicholas “cut-off ramp” Study

• WSI purpose set out in a 1995 TEAP Project was: “To define an index to objectively measure pedestrian security at intersections including comfort and convenience as well as safety components”


What are the purposes of WSI?

• To provide a means of better describing the walking security experience of pedestrians at signalized intersections;

• To provide a means of better explaining why pedestrians’ experiences differ from their expectations in regard to security;

Source: Walking Security Index Report (p 32) – Wellar, July 1998


Purposes of WSI

• To provide a means of better evaluating the consequences for pedestrians’ security that are likely to arise from proposed modifications to signalized intersections, infrastructures, and/or to the behaviors of intersection users.

• To provide a means of better predicting the consequences for pedestrians’ security that are likely to occur as a result of intersection infrastructure modifications and/or changes in the behaviors of users; and,



WSI Formulations:

1. Vehicle-Pedestrian Interaction Potential (V-PIP) Index

V-PIP = # of vehicles/hr x # pedestrians/hr …(1)

Source: Walking Security Index Report – Wellar, July 1998


WSI Formulations:

1. Vehicle-Pedestrian Interaction Potential (V-PIP) Index V-PIP = # of vehicles/hr x # pedestrians/hr …(1)

Source: Walking Security Index Report – Wellar, July 1998

2. Weighted Vehicle-Pedestrian Interaction Potential (WV-PIP) Index

WV-PIP = # of vehicles²/hr x # of pedestrians/hr …(2)


WSI Formulations

3. Weighted Passenger Car Equivalent-Pedestrian Interaction Potential (WPCE-PIP) Index

Source: Walking Security Index Report (p 41 - 47) – Wellar, July 1998

WPCE-PIP = # of passenger car equivalents²/hr x # of pedestrians/hr …(3)

Where: automobile = 1.0 passenger car equivalent;heavy vehicle = 1.7 passenger car equivalent; and, bus = 1.7 passenger car equivalent.


WSI Formulations

4. Quality of Infrastructure Condition (QIC) Index

18 variables pertaining to intersection construction or maintenance features …(4)

Source: Walking Security Index Report (p 47, 48) – Wellar, July 1998

• It’s purpose is to provide an assessment of whether intersection features involving infrastructure construction and maintenance meet pedestrians’ security expectations.


QICI Field Form


WSI Formulations


5. Intersection Pedestrian Challenge-Features (IPC-F) Index

IPC-F = NLR x NTLTR x IGR x ISR x DTFR x NCR …(5)

Where:NLR = number of lanes rating NTLTR = number of lanes by type rating IGR = intersection geometry rating ISR = intersection slope rating DTFR = direction(s) of traffic flow rating NCR = number of channels adjacent to intersection rating


WSI Formulations


6. Basic Walking Security (BWS) IndexBWS = (WPCE–PIP) x (IPC-F) …(6)

Where:BWS = a composite index score that ranks signalized intersections according to the likelihood that pedestrians’ security expectations are matched by experiences.WPCE–PIP = an index score that represents the quality of potentialinteractions between pedestrians or vehicles (expressed as passenger car units) at signalized intersections.IPC-F = an index score that represents the magnitude of challenge to pedestrians’ security caused by intersections’ features.


WSI Formulations


Aggressive Driving Indexes: (AD_)

(ADR) Index: Red = # of vehicles through on red/hr total # of vehicles/hr …(7)

(ADA) Index: Amber = # of vehicles through on amber/hr total # of vehicles/hr …(8)

(ADRA) Index: Red + Amber = # of vehicles through (red+amber)/hr total # of vehicles/hr

…(9)


WSI Formulations


(ADFY) Index = # of vehicles that fail to yield to pedestrians/hr total # of vehicles/hr …(10)

Aggressive Driving Fail-to-Yield (ADFY) Index

The fail to yield index applies in all those crosswalk and channel situations where vehicle operators engage in behaviors thatthreaten pedestrians’ security:


Report on WSI - July 1998

• Study resulted in 17 Recommendations

• Staff supported 11 – current policy or were technically supportable• Staff could not support the remaining recommendations - some were contrary to Highway Traffic Act


Report on WSI – July 1998

• Following consideration of the WSI Report, the researcher presented a proposal to Transportation Committee, asking that the Study be extended

• Committee and Council approved the proposal for a pilot study that would provide a more robust sample of field data to refine indexes and variables in WSI• Field testing was intended to confirm operationality, not utility• Resulted in 6 Technical Reports and Final Pilot Study Report received in May 2002 (Annex 2)

• Staff were not consulted beforehand


WSI Refinements

6. Basic Walking Security (BWS) IndexBWS = (WPCE–PIP) X (IPC-F) …(6)

Where:V1 = number of passenger car equivalents/hourV2 = number of pedestrians/hourV3 = number of lanes rating V4 = number of lanes by type rating V5 = intersection geometry rating V5 = intersection slope rating V7 = direction(s) of traffic flow rating V8 = number of channels adjacent to intersection rating

Revised to: Intersection Volume and Design (IVDI) Index IVDI = V1 x V2 x V3 x V4 x V5 x V6 x V7 x V8


WSI Refinements

DBI = ALI + RLI + FTYI P P P …(11)

Where:ALI = amber-light incidents per phase, P RLI = red-light incidents per phase, PFTYI = fail-to-yield incidents per phase, P

Aggressive Driving Indexes: Formulas …(7), (8), (9), (10)were combined to become: Driver Behaviour Index (DBI)


WSI …What is it?

• WSI is a composite index– Intersection Volume and Design Index (IVDI)– Quality of Infrastructure Condition Index (QICI)– Driver Behaviour Index (DBI)

• Examines 39 variables in four quadrants of each intersection being reviewed

• 33 intersections were examined in the Pilot Study since 1998, resulting in over 200 tables


WSI …What does it do?

• Purports to describe the walking security experience of pedestrians at signalized intersections …but does it?• Purports to provide a score ranking of pedestrians’ experiences in relation to their expectations … but does it?

• Example of Ranking …


WSI …Staff concerns

• We are committed to improving safety for all road users, especially vulnerable road users (pedestrians, cyclists, seniors, disabled) – WSI does not consider pedestrian types or cyclists • WSI does not consider collision experience• WSI does not consider pedestrian disregard for traffic signals• WSI data collection requirements are far too onerous and costly to perform by City staff• WSI cannot be used to prioritize safety improvements through any form of cost/benefit analysis


WSI …Staff concerns

• WSI does not appear to be technically sound or legally defensible

• Use of the WSI to rank priorities for roadway infrastructure modifications for the limited funds available, could needlessly expose the City to liability/litigation


Why was a Transportation Engineering Consultant retained to conduct a Technical Review of the WSI Project?

• To provide an objective, independent, expert assessment of the WSI with respect to:

• Technical validity

• Mathematical soundness - through examination of:Indexes on which it is based and

Weighting assigned to index variables

• Data collection and input requirements

• Defensibility in court should liability issues arise as a result of WSI


Why was a Transportation Engineering Consultant retained to conduct a Technical Review of the WSI Project?

• To asses the results it produces against outcomes derived from the application of existing Traffic Engineering techniques, approved by that profession as being both cost-effective and sound engineering practice


What are we doing to improve safety for Vulnerable Road Users?

• Extracting information from over 13,000 Motor Vehicle Accident Reports annually to maintain an up-to-date collision database• Implementing remedial measures at “high collision locations” and other sites of concern through our Safety Improvement Program• Responding to over 7,000 citizen concerns and service requests for traffic and street lighting services per year • Conducting over 800 traffic surveys per year to address the need for new all-way stop controls, traffic control signals, pedestrian signals, Adult Crossing Guards



• Providing “Rules of the Road” awareness to children through our Elementary School Outreach Program• Providing new sidewalks and recreational pathways each year• Providing new cycling lanes as part of all road construction and intersection modification projects• Installing audible features at new traffic control signals installation • Participating in the Red Light Camera Pilot Project



• Learning from experience where right-turn cut-off ramps should not be constructed, or even considered, in view of pedestrian activity

• Installing over 20 new traffic control and pedestrian signals in 2003

• Working in partnership with Police Services and the Health Department to develop and deliver the Integrated Road Safety Program, that focuses on the needs of Vulnerable Road Users


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Dr. John Robinson

pedestrian safety at intersections assessment of the walking security index - wsi safety and traffic...

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