Synthesis of Safety for Traffic Operations - Transports Canada

Synthesis of Safety for Traffic Operations March 2003
condition) is the traditional red, yellow, green signal arranged vertically, with 300mm,
200mm, and 200mm lenses, respectively. The standard installation also included a
yellow backboard. The treatment was to increase the size of the yellow and green lenses
to 300mm each, and to place a 50mm reflective border on the backboard.
The intersections under study were four-leg intersections with left-turn channelization,
and three or four lanes on each approach. Primary signal heads were mast-arm mounted,
while the secondary heads were post-mounted. The visibility was considered adequate
for the posted speed limit, and the setting was an urban, commercial/retail area.
The study methodology was a before-after study with a control group, using Empirical
Bayes techniques to account for regression-to-the-mean. Crash frequency and severity
were the measures of effectiveness, with one year of before, and two years of after data
being available. The results are shown in Table 3.31.
TABLE 3.31: Safety Impacts of Alternative Signal Head Design in BC
Site
CMF
All Crashes Injury+Fatal
1 0.57 0.74
2 0.55 0.68
3 0.66 0.89
4 0.90 0.88
5 0.59 0.54
6 1.10 1.29
7 1.29 1.77
8 0.58 0.90
9 1.05 0.89
10 0.62 0.46
Average 0.79 0.91
Transportation Association of Canada (2001)
Phase 2 of this study (TAC, 2001) included an investigation of the safety impacts of
diamond-grade TM yellow reflective tape on the signal head backboard. The tape was
placed on the outside edge of the backboard and was 75 mm wide. Six intersections in
British Columbia were outfitted with the new heads and studied for a one-year before,
and a three-year after period. The safety analysis examined only night-time crashes.
Results are as shown in Table 3.32.
TM Diamond-grade is a trademark of 3M Company.
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