Synthesis of Safety for Traffic Operations - Transports Canada

Intersection Control
It is noted that 11 of the 38 sites had multiple interventions and therefore any safety
impact cannot be attributed to the signal lens alone. The results of the Polanis study,
minus the sites with multiple interventions, are presented in Table 3.38.
TABLE 3.38: Safety Impacts of 12 inch Signal Lenses
Site
Target Crashes
Total Crashes
Before After Change* Before After Change*
1 4 0 -100 11 7 -35
2 14 1 -93 31 13 -58
3 20 2 -92 43 25 -53
4 8 1 -87 48 35 -22
5 12 2 -83 33 20 -39
6 10 2 -80 24 9 -63
7 15 3 -80 43 38 -12
8 8 2 -75 24 20 -17
9 17 4 -74 30 21 -21
10 4 1 -71 14 21 +71
11 11 4 -58 28 12 -51
12 12 5 -58 12 6 -50
13 9 3 -57 35 23 -15
14 15 7 -53 49 38 -22
15 15 8 -47 29 38 +31
16 14 8 -45 40 33 -21
17 16 9 -44 26 23 -12
18 12 7 -42 26 13 -50
19 17 12 -31 28 25 -13
20 11 8 -27 15 17 +13
21 8 6 -25 20 13 -35
22 10 8 -20 19 18 -5
23 9 8 -11 23 23 0
24 25 23 -8 41 52 +27
25 14 13 -7 22 22 0
26 8 9 +13 13 14 +8
27 8 13 +63 23 27 +17
* Change is based on crashes/month due to unequal before and after periods.
The average reduction in target (angle) crashes is 48% or a CMF of 0.52; the average
reduction in all crashes is 16% or a CMF of 0.84. Exposure was not accounted for in the
analysis. Assuming that traffic volumes either remained constant or increased (as tends
to be the case) the CMFs are conservative. However, it cannot be determined if the site
selection process introduced any bias into the study results.
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