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Patrick HassonFederal Highway Administration
Midwestern Resource Center
Engineering Safer Intersections
Crash Cause by Factor
Vehicle
12%
RoadwayRoadway
34%34%
DriverDriver
93%93%3 %3 % 57 %57 %
2 %
27%27%
6 %6 %1 %1 %3 %3 %
Program History
Created by FHWA in 1995 as community based safety program – 31 communities.
Expanded in 1998 with DaimlerChrysler and American Trauma Society.
MISSION
To continually reduce the incidence of red light running in order to prevent related crashes, trauma center admissions
and fatalities.
Background – The Numbers
Fatality rate dropped 12% from 1992 to 1998.
10% decrease in fatality numbers from 1996 to 1999 – our most aggressive years. 60,000
70,000
80,000
90,000
100,000
1992
1993
1994
1995
1996
1997
1998
1999
crashes
injuries
1000
1100
900
91,000 Crashes 90,000 Injuries
956 FatalitiesEstimated $7 Billion a year in costs
Background - Products
Step by Step Guide Synthesis and Evaluation of
RLR Automated Enforcement Programs
Association of Selected Intersection Factors with Red Light Running Crashes
Web Pagewww.fhwa.dot.gov
Various Articles
Dichotomized Driver
Population
RLR Driver Type
Possible Scenario
Countermeasure Class
Engineering Enforcement
“Intentional” Congested, Cycle overflow
Less MostEffective
“Unintentional” Incapable (grade, Y)Inattentive
MostEffective
Less
0
P(stop)
0
1
Travel Time, s4 8
IntentionalUnintentional
Courtesy TTI
Theoretical analysis
Intersection entry categorieslegal safe intentional typical time after red
Ayes yes yes green/yellow
Bno yes yes 0 to ~1
Cno no yes ~1 to 3+
Dno no no 3- to green entry types B and C most amenable to cameras entry types C and D can cause RLR crashes
… focus on type C intersection entries
Courtesy NC State
Engineering Solutions?
Insufficient information on full range of possible improvements.
Evidence that engineering can be effective –UK, Michigan, HSIS, Others.
Challenge: Criteria to guide jurisdictions in reviewing the safety of their intersections could aid better decision making.
FHWA/ITE Project
“Practitioners Guide” Stand-alone to make an
intersection safer. Describes engineering
features that should be examined prior to applying automated enforcement.
PLAY IT SAFESTOP FOR RED LIGHTS!
PHOTO ENFORCEDCity of Baltimore
Spring 2002
Related Information
Ongoing/Completed Research Projects– North Carolina (NC State)
www.itre.ncsu.edu/rlr
– Texas(Texas Transportation Institute) Identify factors affecting RLR frequency Develop model of the RLR process Identify candidate countermeasures
Municipalities using cameras do engineering review prior to camera installation.– Reviews are inconsistent in coverage/approach
Engineering SolutionsCan Make a Difference
1. Signal timing, type, lens size, and placementi. Clearance intervals (all red phase)ii. Length of yellow phase
2. Sight distance3. Unwarranted or non-standard signal removal4. Geometrics -vertical curvature and mainline road width5. Speed and volume/capacity6. Intersection Advance Warning Flashers7. Pavement Treatments (skid resistance and markings)8. Left turn lanes and phases9. Pedestrian Signals
Theory:RLR Exposure Events
1. Flow rate on the subject approach
2. Number of signal cycles
3. Probability of max-out
4. Yellow interval duration 0
P(rlr)
0
1
Volume
0
P(rlr)
0
1
Cycle Length 0
P(rlr)
0
1
P(max-out)0
P(rlr)
0
1
Yellow Int.Courtesy TTI
Theory:Driver Behavior
Factors
1. Travel time
2. Speed
3. Actuated control
4. Coordination
5. Headway
6. Approach grade
7. Yellow interval
8. Expected delay
9. Signal visibility0.0 1.0 2.0 3.0 4.0 5.0 6.0
Travel Time to Stop Line, s
0.0
0.2
0.4
0.6
0.8
1.0Probability of Stopping
35 mph
55 mph
Courtesy TTI
Measures of Effectiveness?
1. Number of vehicles running red
2. Number of vehicles in or entering
intersection when conflicting phase is green
3. Number of vehicle-vehicle conflicts
Intent of yellow interval: provide time to reach the stop/go bar if no room to stop– one safe move (stop or go) usually provided
assumptions: 1.0 sec reaction, 10 ft/sec2 decel. rate “standard” driver still must choose correctly
– not all drivers can meet standard assumptions older drivers: 1.5 sec reaction time distracted time: 1.25 sec is typical
DILEMMA ZONE AND YELLOW TIME
Courtesy NC State
for speed limit 40 MPH (NCDOT standard Y = 4.0 sec)
reaction decel dilemma dilemma time, (t) rate, (a) distance time
sec ft/sec2 ft sec
1.0 10 -4 -0.11.0 9 15 0.31.5 10 25 0.41.5 11 10 0.2
DILEMMA ZONE AND YELLOW TIME
Courtesy NC State
for speed limit 55 MPH (NCDOT standard Y = 5.1 sec)
reaction decel dilemma dilemma time, (t) rate, (a) distance time
sec ft/sec2 ft sec
1.0 10 -6 -0.11.0 9 31 0.41.5 10 35 0.4
DILEMMA ZONE AND
YELLOW TIME
Courtesy NC State
ENGINEERING COUNTERMEASURES
Increase yellow duration
Courtesy TTI
VERTICAL CURVATUREAND MAINLINE WIDTH
All Red Clearance Interval
Michigan Study
Left turn Lanes and Phases
ENGINEERING COUNTERMEASURES
Provide advance warning of yellow interval
Courtesy TTI
Sometimes alternatives such as roundabouts can provide significant safety and operational benefits.
ENGINEERING COUNTERMEASURES
ENGINEERING COUNTERMEASURES
Alternative intersection designs can reduce major conflict points.
52
44
Concepts for Intersection Collision Avoidance
Infrastructure-based systems can:– Warn “violating” driver to obey traffic signal,
stop sign, or railroad crossing signal
– Warn other drivers of potential conflict with violating driver
– Advise drivers when safe to turn at traffic signal or to move away from stop sign
– Warn drivers of potential conflict with pedestrian or pedalcyclist
Traffic Signal Violation Warning
Prototype Strobe
Roadside Flashing Warning Sign
Intelligent Rumble Strips
Warning Sign for Other Drivers
Keys to Successful Red Light Camera Programs
Traffic safety focus Public acceptance
– Education– Explain where the money goes; – Fairness: Infrastructure or behavior?
Legislative, Judicial and Enforcement support Learn from the experience of others High level of “customer service” (answer
violator calls)
