Synthesis of Safety for Traffic Operations - Transports Canada

Intersection Control
TABLE 3.54: CMFs for Adding Left-Turn Phasing (Thomas and Smith)
Crash Type Mean # Sites
90% Confidence Intervals
Lower Upper
Fatal N/A 0 N/A N/A
Major 0.78 3 2.58
Severity Minor 0.50 4 1.01 0.00
Possible 0.63 4 1.35
PDO 0.71 4 1.19 0.24
Right-angle 0.70 3 1.24 0.15
Impact Type
Rear-end 1.00 4 1.80 0.20
Left-turn 0.49 4 1.05
Other 1.60 4 2.75 0.45
Total 0.64 4 0.77 0.52
In the same study, Thomas and Smith investigated the effects of adding turn phasing in
conjunction with adding an exclusive left-turn lane(s). The study methodology was
similar, a total of seven sites were investigated. The results are as shown in Table 3.55.
TABLE 3.55: CMFs for Adding Left-Turn Phasing and Turn Lanes (Thomas and
Smith)
Crash Type Mean # Sites
90% Confidence Intervals
Lower Upper
Fatal 0.00 2 N/A N/A
Major 0.15 5 0.34
Severity Minor 0.25 6 0.34 0.17
Possible 0.49 7 0.66 0.32
PDO 0.43 7 0.58 0.28
Right-angle 0.48 7 0.72 0.23
Impact Type
Rear-end 0.63 7 0.97 0.28
Left-turn 0.27 7 0.38 0.16
Other 0.55 7 0.74 0.37
Total 0.42 7 0.54 0.30
The results indicate that the addition of left-turn phasing in conjunction with exclusive
turn lanes yields safety benefits in all categories, except for fatal crashes where no
statistically significant findings are available.
Chin and Quddus (2001)
Chin and Quddus (2001) developed crash prediction models for four-legged, signalized
intersections using eight years of crash data from 52 intersections in Singapore. The
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