Synthesis of Safety for Traffic Operations - Transports Canada

Turn Lanes
CMF = 1 – 0.7 P lt/d
0.0047D + 0.0024D 2
1.199 + 0.0047D + 0.0024D 2 [9.3]
where:
P lt/d = proportion of driveway-related crashes that are left-turn
crashes susceptible to relief by a 2WLTL expressed as a decimal
D = Driveway density (driveways/mile)
In the absence of information on the proportion of left-turn crashes that are susceptible to
relief by a 2WLTL, it may be assumed that it is 50% of the total driveway-related
crashes.
Right-turn lanes
Vogt and Bared (1999)
Vogt and Bared (1999) found that the presence of a right turn lane on the main road of a
stop-controlled “T” intersections in rural Minnesota was associated with a CMF of 0.79.
This finding was statistically significant, although the same result was not found for rural,
stop-controlled cross intersections.
Bauer and Harwood (2000)
In a comprehensive crash modelling exercise conducted by Bauer and Harwood (2000) a
right turn lane on the main road at 4-leg, rural, stop-controlled intersections was
associated with a CMF of 0.85. CMFs for other intersection and lane configurations are
shown in Table 9.15.
TABLE 9.15: CMFs for Turn Lanes at Different Intersection Types
Intersection Lane type CMF
Rural, 4-leg, stop
controlled
Right turn on main road 0.85
Rural, 3-leg, stop
Painted left turn on main road 0.81
controlled Curbed left turn on main road 0.91
Urban, 4-leg, signalcontrolled
Right-turn Channelization on major road 1.12
Urban, 4-leg, stopcontrolled
Right-turn Channelization on cross road 1.47
Urban, 3-leg, stopcontrolled
Right-turn Channelization on cross road 1.75
Painted left turn on main road 0.98
Curbed left turn on main road 1.21
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