Synthesis of Safety for Traffic Operations - Transports Canada

Intersection Control
TABLE 3.23: CMFs for Conversion to All-way Stop
Crash Type SF Philly Michigan Toronto Combined
No. Sites 49 222 10 79 360
Right-angle 0.16 0.22 0.36 0.52 0.28
Rear-end 3.05 0.80 0.81 0.78 0.87
Left-turn 0.67 --- 1.07 0.75 0.80
Pedestrian 0.34 0.60 --- 0.58 0.61
Fixed object --- 1.30 --- --- ---
Injury 0.26 0.26 0.38 0.37 0.29
Total 0.38 0.53 0.41 0.63 0.53
Laplante and Kropidlowski (1992)
Laplante and Kropidlowski (1992) studied the safety impacts of all-direction stop control
on arterial roads in Chicago. Thirty intersections were studied; 16 of these locations met
the warrants for all-direction stop control, the remainder were unwarranted. Traffic
volumes on the arterial streets ranged from 3,000 to 23,000 vehicles per day. The side
streets were local streets with daily volumes of less than 3,000 vehicles.
The study methodology is a before-after analysis of crash frequency using three years of
before, and three years of after data. In addition, the researchers gathered an additional
three years of data from 10 years after the initial installation to determine if the safety
impacts varied over time. The results are shown in Table 3.24.
TABLE 3.24: CMFs for All-direction Stop Control in Chicago
Crash Frequency
All-way Number Crash (crashes/year)
CMF
STOP Type of Sites Type
10 years
10
Before After
Immediate
After
year
Warranted 16
All 11.0 4.6 3.2 0.42 0.29
Angle 6.8 1.5 1.4 0.22 0.21
Unwarranted 14
All 3.4 4.2 2.2 1.24 0.65
Angle 1.4 0.8 0.8 0.57 0.57
Unwarranted
All 3.2 1.4 0.8 0.44 0.25
ADT < 3
12,000
Angle 1.0 0.5 0.3 0.50 0.30
Unwarranted
All 4.1 10.8 7.0 2.63 1.71
ADT > 3
12,000
Angle 1.7 2.2 2.2 1.29 1.29
The Laplante and Kropidlowski study results indicate that warranted all-direction stop
control are effective at reducing angle and total crashes. The unwarranted all-direction
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