Synthesis of Safety for Traffic Operations - Transports Canada

Intersection Control
Signal Clearance Timing
Lalani (1991)
The City of San Buenaventura, California as part of a Comprehensive Safety Program
improved the clearance timing at three signalized intersections (Lalani, 1991). Sites were
selected because they were considered high crash locations. The analysis was a naïve
before-after analysis using crash frequency and one-year before and after periods. Details
of the treatment are not reported (i.e., what was the original clearance timing? And what
was the exact countermeasure?). Nonetheless, the safety impacts of the improved signal
timing are shown in Table 3.41.
TABLE 3.41: Safety Impacts of Improved Clearance Timing in California
Location
Crashes
Before After
CMF
A 17 7 0.41
B 7 4 0.57
C 10 6 0.60
Totals 34 17 0.50
Lalani does not account for exposure in the safety analysis but reports that traffic
volumes in the city increase at an average rate of 6% per annum.
Signal Coordination
Lalani (1999)
The City of San Buenaventura, California as part of a Comprehensive Safety Program
introduced coordination to at least three areas of the city (Lalani, 1991). Sites were
selected because they were considered high crash locations. The analysis was a naïve
before-after analysis using crash frequency and one-year before and after periods. Details
of the treatment are not reported. Nonetheless, the safety impacts of the improved signal
coordination are shown in Table 3.42.
TABLE 3.42: Safety Impacts of Signal Coordination in California
Location
Crashes
Before After
CMF
A 179 129 0.72
B 16 12 0.75
C 129 103 0.80
Totals 324 244 0.75
Page 48