Synthesis of Safety for Traffic Operations - Transports Canada

Synthesis of Safety for Traffic Operations March 2003
TABLE 3.48: Safety Effects of Changing Left-turn Phasing In Arizona
Treatment No. Sites Left-turn Crash Rate
CMF
Before After
Two Opposing Lanes
P # Lead E/P 17 4.77 3.49 0.73
P # Lag E/P 9 5.44 4.16 0.76
Lead E/P # P 14 2.07 2.66 1.29
Lead E/P # 35 3.10 2.25 0.73
Lag E/P
Lead E # Lead 3 0.93 3.11 3.34
E/P
Lead E # Lag 6 0.38 1.57 4.13
E/P
Lead E # Lag 10 1.46 1.91 1.31
E
Three Opposing Lanes
P # Lead E/P 3 4.64 5.55 1.20
P # Lag E/P 8 8.75 1.37 0.16
P # Lead E 3 18.96 0.36 0.02
Lead E/P # P 3 2.25 5.85 2.60
Lead E/P # 38 4.54 2.74 0.60
Lag E/P
Lead E/P # 2 7.08 0.75 0.11
Lead E
Lead E # Lead 22 1.40 4.72 3.37
E/P
Lead E # Lag 9 2.13 1.03 0.48
E/P
Lead E # Lag
E
12 0.35 0.35 1.00
The CMFs from the Arizona study are largely consistent with intuition:
• Changing from a permissive movement to a more restrictive movement (either
exclusive-permissive or exclusive) is associated with a safety benefit;
• Changing from an exclusive-permissive movement to an exclusive movement is
generally beneficial from a safety perspective; and
• Changing from a restrictive movement to a more permissive movement is
associated with degradation in safety.
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