Synthesis of Safety for Traffic Operations - Transports Canada

Synthesis of Safety for Traffic Operations March 2003
TABLE 3.27: Safety Impacts of Signal Upgrades in South Dakota
No.
Crashes
EPDO Crashes*
Improvement AADT
of
Type
Range Before After CMF Before After CMF
Sites
Signal
5085 -
6
272 180 0.66 4673 2635.5 0.56
Upgrading
28200
* EPDO crashes were calculated as (1300*F)+(90*I)+(18*N)+(9.5*P)+PDO
where: F = fatal crash
I = incapacitating injury crash
N = non-incapacitating injury crash
P = possible injury crash
PDO = Property damage only crash
Transport Research Laboratory (2000)
The TRL (2000) of the United Kingdom has collected information on the safety impacts
of signal modifications through the MOLASSES database (see the section on
“Signalization” for more information on MOLASSES). The definition of “signal
modification” is not provided, so the results are generalized and are only adequate to
provide cursory guidance on the magnitude of the potential for safety improvement. The
results are shown in Table 3.28.
TABLE 3.28: Safety Effects of Signal Modifications in the United Kingdom
Number of Number of Crashes
Setting
Locations Before After
CMF
Urban 80 1130 697 0.62
Rural 10 135 66 0.49
Signal Conspicuity
Cottrell (1995)
The use of white strobe lights as a supplement to the red signal indication at six traffic
signals in Virginia was evaluated by Cottrell (1995). The strobe light was a horizontal
bar pattern that was placed concentric with the red lens of the signal lens. Three years of
before, and three years of after crash data were used in a naïve before-after analysis of
crash frequency.
The characteristics of the study intersections are displayed in Table 3.29. The results of
the crash analysis are shown in Table 3.30.
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