pedestrian collision warning demonstration … · pedestrian collision warning demonstration...
TRANSCRIPT
PEDESTRIAN COLLISION
WARNING DEMONSTRATION
PROJECT
Approach and Findings
Presented by
Harry Saporta
Kelley Klaver Pecheux, PhD
2015 APTA Bus and Paratransit Conference May 5, 2015
Study team
Study objectives
Technologies assessed/tested
Test approach
Evaluation approach
Findings
Overview of Presentation
Study Team
Study was funded through an FTA Cooperative Agreement
Study was conducted by
TriMet
Applied Engineering Management Corporation (AEM)
Portland State University (PSU)
Study Objectives
Demonstrate the ability of various commercially-available turn warning
systems to provide timely warning to pedestrians/cyclists that a bus is
turning or pulling into/away from a bus stop.
Determine the effectiveness of the turn warning systems at intersections and
bus stops.
Determine the benefit-cost ratios associated with the turn warning systems.
Define the environmental parameters under which advance warning should
be provided to pedestrians/cyclists at intersections and at bus stops.
Assess the effectiveness of an innovative warning sign at one intersection.
Technologies Assessed/Tested
Three commercially-available turn warning systems:
Turn warning system 1
Spoken warning activated by rotation of steering wheel
Included two LED strobe lights on either side of the bus
Turn warning system 2
Spoken warning activated by rotation of steering wheel
Turn warning system 3
Beeping warning activated through use of the turn signal
Included directional LED headlights
“BUS” blank-out sign
Activated by a bus waiting to turn at an intersection (signal actuation)
Concept for the sign was developed by AEM
Test signs were designed and built by TriMet
Signs were installed by the City of Portland
A fourth commercially-available turn warning system was assessed but not tested
Spoken warning activated through use of the turn signal
Test Approach
45 buses equipped with systems (15 buses with each of the 3 turn warning
systems).
All test buses call came out of one maintenance facility.
Each day, test buses were placed on 5 pre-selected test routes:
Pre-determined number of each system on each route (ranged from 2-4,
generally 3, depending on the total number of buses on each route)
One test route was replaced halfway through the test due to public complaints.
“BUS” blank-out sign placed at both ends of one crosswalk at a busy
intersection in downtown Portland.
Test ran 7 months (March-September 2014).
Evaluation Approach
Bus operator surveys
Daily surveys conducted 3 times per week for 13
weeks
436 completed surveys
Comprehensive bus operator survey
208 completed surveys
Pedestrian surveys
Field intercept surveys administered at 5
intersections
454 completed surveys
Evaluation Approach (cont’d)
Bus operator focus groups
4 focus groups with 27 operators
Pedestrian focus groups
3 focus groups with 27 pedestrians
Analysis of pedestrian behaviors
80 hours of video data collected at 4 intersections
Interviews with TriMet staff
Cost-benefit analysis
Overview of Findings
There were a number of common themes that emerged
throughout the study.
There was a (somewhat wide) range of feedback
regarding perceptions, acceptance, and
recommendations for improving the technologies
representing mixed findings.
Benefit-cost analysis
Warning volume – finding an appropriate volume
level for the warnings
Sensitivity of warning activation – finding the right
sensitivity setting for warning activation
Warning - selecting the right warning type/content
Application of the warnings – determining when
and where the warnings should activate
Common Themes
Warning Volume
Getting the volume of the warnings right was an issue throughout the
demonstration test.
Early complaints from operators and residents led to volume adjustments.
Noise complaints declined, but a growing number of operators reported in the
daily surveys that the volumes had become too low to be effective.
Overall lack of consensus in feedback:
Operator responses showed that the “too loud” margin was significantly greater for systems with
the spoken warning than for the system with the beeping sound.
A majority of pedestrians surveyed did not find the warnings to be intrusive to the environment.
Of those that did, more found the spoken warnings to be intrusive than the beeping warning.
Participants in the pedestrian focus reported that the volumes of the spoken messages were
acceptable once they were adjusted, but that the beeping warning was still too loud.
Repetition and/or frequency of warnings may also play a role.
Sensitivity of Warning Activation
Specific to the systems activated by rotating the steering wheel.
Activation angles for both systems were initially set to provide early warnings.
Initial turn angles produced false activations of the warnings in certain situations.
Mitigated somewhat via system adjustments to one of the systems, which was evidenced by a downward trend in the reporting of false activations in the daily operator survey.
A majority of operators still indicated in the comprehensive survey that the systems activated too early and/or in roadway curves.
Operator focus groups confirmed that the problems were mitigated somewhat via system adjustments but continued in some cases.
Speed threshold may also play a role.
Warning Type/Content
Operators were most divided over the beeping warning:
Some preferred it over the spoken warnings because it is “universal” and/or more effective at getting people’s attention.
Others did not like it because it was too loud, harsh, irritating, and potentially distracting.
Strong consensus that “caution” is better than “pedestrians.”
In addition to warnings used in the demonstration test, a variety of auditory warnings were presented to and discussed with focus group participants:
Shorter, concise warnings were generally preferred over longer, more detailed warnings.
“Caution, bus is turning” was rated above all others and was favored by most.
A recommendation from both operators and pedestrians:
Easily-recognized and unique to TriMet buses, as well as “friendly.”
Warning that incorporates both a spoken warning and a sound/tone.
Application of the Warnings
Overwhelming agreement by operators that the turn warnings are important, if not more
important, at bus stops than at intersections (pedestrians tended to agree).
Generally (slightly) more necessary during right turns (as opposed to left turns) and when pulling
into a stop (as opposed to pulling away from a stop).
Two recurring issues suggest that it may be prudent to consider selective versus ubiquitous
application of the turn warnings:
Early complaints - giving more thought to where the warnings should activate (and at what times of the day) could
help to avoid these types of complaints.
Long-term efficacy - bus operators and pedestrians believed that the warnings would eventually blend into the
background noise and/or be tuned out.
Both operators and pedestrians strongly recommended that the volumes vary by location and/or
time of day or that the volumes adjust automatically relative to the environment.
Alternatively (or additionally), participants recommended that warnings activate only on
“trouble” routes/locations and/or at locations with history of conflicts.
Flip side – issue of liability if a pedestrian is struck at a location or time of the day when the
warnings are inactive.
Important to involve the community when selecting locations.
Wide Range/Mixed Feedback Regarding:
Perceptions of technology effectiveness
Acceptance of the technologies
Recommendations for improving the
technologies
Perceptions of Technology Effectiveness
Overall, bus operators were generally less favorably impressed with the effectiveness of
the turn warning systems than the general public:
As is, the turn warning systems are only somewhat effective at improving safety (system and
pedestrian related).
Improvements, programming/customization, and some added operator control features could
make the systems more effective.
Systems not the “be-all-end-all” to reducing pedestrian-bus collisions (operator and pedestrian
accountability).
The warnings are as or more effective at service stops than at intersections, with pulling into a
stop being the more critical movement.
The turn warning systems are less effective with cyclists than with pedestrians.
LED cornering headlights highly effective at improving visibility in the direction of the
turn.
A fair majority of pedestrian respondents felt that the systems were effective at both
alerting pedestrians and improving pedestrian safety.
Just over half of pedestrian respondents found the BUS blank-out sign to be effective at
alerting pedestrians that a bus is turning and at improving pedestrian safety.
Acceptance of Technologies
Operators:
Nearly half of operators surveyed agreed that the potential safety benefits outweighed the drawbacks of the warning systems.
However, overall, only about one third agreed with the prospect of wider deployment, while nearly half disagreed.
General sentiment from focus groups regarding further deployment could be described as ranging from apathetic to skeptical – most seemed to have adapted to the presence of the warnings, but did not strongly support nor completely reject the idea of their continued or expanded use.
Pedestrians:
A majority of pedestrians surveyed did not find the warnings to be intrusive to the environment.
Further, a majority agreed that more systems should be installed.
A small group agreed that the potential benefits outweighed the associated drawbacks, but disagreed with the idea of further deployment. Could be associated with costs – money better spent elsewhere.
Recommendations for Improving
Technologies
“Tweak” the systems and “get the bugs out.”
Tie the system to the turn signal (as opposed to the steering wheel).
Select a lower speed threshold for warning activation.
Integrate systems with GPS/AVL system to be more programmable.
Operator control
Most operators agreed that total operator control over the system was not a good
idea.
Some operators advocated for some level of control (e.g., volume and when
warning could be sounded).
Others strongly recommended that operators be given no control over the system.
If more programmable, would reduce/eliminate need for any operator control.
Imputed Benefits Framework
Bus-pedestrian collisions resulting in injuries or fatalities are rare events.
2010 National Transit Database – 27 fatalities and 283 injuries requiring transport in association with 1.6 billion
miles of revenue service.
This translates to about 1.7 fatalities and 17.7 injuries per 100 million revenue service miles.
TriMet’s entire bus system logs approximately 20 million revenue service miles per year.
A research design predicated on documenting changes in fatalities and injuries on six routes over a 7-month
period would likely find no “treatment effect” attributable to the turn warning systems.
Drew on safety pyramid concept – Bus-pedestrian close-calls more common than actual
collisions. Given a defined hierarchy of safety risks and outcomes, it is possible to
impute the expected incidence of pedestrian fatalities and injuries in relation to the
frequency of close-calls.
Employed relative frequency data specific to close-calls
and collisions involving buses and pedestrians (national and
transit property data) to operationalize the safety
pyramid for this study.
Imputed Benefits
National data – 2010 NTD
Fatalities and injuries requiring transport
Transit property data – TriMet
Safety information system (Dec ’10-Oct ‘14)
Bus-pedestrian collisions, injuries (requiring transport minor,
none)
Close-calls
Pedestrian close-call button (since 2013) – not well
documented (under reported) by operators
Data from 2012 survey of risk perceptions – frequency of
total close calls
Evasive action/hard stop events due to pedestrians
Daily operator surveys – reported reduction in close calls
due to turn warning systems
1.0
10.5
30.0
37,723
Incident Types Close-Calls per
Incident
Annual Avoided
Incidents
Years to
Realize
Fatality 37,723 0.037 27
Injury (transport) 3,593 0.393 2.5
Minor or No Injury 1,257 1.124 11 months
Cost-Benefit Framework
Guidance from
OMB Circular A-94
Information on discounting
Treatment of uncertainty
Treatment of the Economic Value of a Statistical Life in
Departmental Analysis, U.S. DOT
Monetary valuation information
12-year cost-benefit analysis timeframe
7% discount rate
Cost Analysis
Accounts for uncertainty by employing a range of values for each key parameter:
Avoided incidents
Valuation of fatalities and injuries
Installation and maintenance costs
Three scenarios
Baseline - employs the baseline cost and benefit component values
Maximum scenario – employs the combination of cost and benefit values that yield the largest achievable net benefit outcome
Minimum scenario – employs component values that produce the smallest net benefit
Results
Cost-Benefit Components Baseline Maximum Minimum
A. Present Value Total Benefits $3,047,131 $7,055,243 $693,591
B. Present Value Total Costs $108,669 $66,205 $151,134
C. Net Present Value (A-B) $2,938,462 $6,989,038 $561,807
D. Ratio of Benefits to Costs (A/B) 28.0:1 106.6:1 4.6:1
E. Internal Rate of Return 34.5% 51.4% 16.5%
Results are for the 45 test buses on the 6 test routes.
Potential elevated relative risk exposure:
While representative of TriMet’s overall network, the test routes are somewhat longer, have
more turns, and serve more passengers than average.
Systems were installed on new buses assigned to base service runs.
Monetary benefits from avoided fatalities/injuries due to the turn warning systems
include social monetary benefits as well as avoided financial liabilities realized by
a transit agency.
Questions?
TriMet Harry Saporta
Safety and Security Executive
(503) 962-4909
AEM Corporation
Kelley Klaver Pecheux
Associate Director of Transportation
(703) 464-7030 ext 8117
Federal Transit Administration
Roy Wei-Shun Chen
Transportation Engineer
(202) 366-0462