Synthesis of Safety for Traffic Operations - Transports Canada

Other Safety Issues
collisions per intersection is a relatively small number and to determine the cause (i.e.,
changed travel patterns, driver unfamiliarity, etc.) would require further analysis.
TABLE 11.2: Crash Migration
Treated Untreated
No. of Intersections 61 277
Crashes recorded before 219 445
Crashes expected after 168 493
Crashes Recorded after 72 575
Change 96 -82
Novelty Effect
A change in traffic control is often associated with a period of driver uncertainty and
adjustment. This is particularly valid on commuter routes where frequent motorists are
not as attentive to traffic control, as the controls are known, or thought to be known from
past driving experience. New controls are potential violations on a priori driver
expectancies and may lead to erratic manoeuvres and crashes.
To examine the decline in safety that is thought to accommodate a change in traffic
control, Persaud (1986) examined the effectiveness of all-direction stop control using
“after” data collected immediately following conversion, compared to “after” data
collected no sooner than six months after conversion. By omitting the first six months of
“after” data in the second dataset, the novelty effect may be determined. The results of
the analysis are shown in Table 11.3, and indicate that there is little or no novelty effect,
or that the overall gain in safety more than compensates for the short-term confusion
caused by the introduction of a new device.
TABLE 11.3: Novelty Effect Associated with Conversion to All-Way Stop Control
Crash Type
CMF
0 months 6 months
Difference
Right-angle 0.21 0.24 0.03
Rear-end 0.83 0.86 0.03
Fixed Object 1.31 1.40 0.09
Pedestrian 0.61 0.54 0.07
Injury 0.27 0.35 0.08
Total 0.55 0.57 0.02
Page 138