Synthesis of Safety for Traffic Operations - Transports Canada

Kermit and Hein (1962) looked into the safety effects of transverse rumble strips at four
locations in Contra Costa, California. All of the test locations were rural approaches to
intersections; two “T” intersections, one “Y” intersection, and one cross intersection.
The rumble strip patterns varied slightly between applications, but were substantially
similar. The study used a naïve before-after methodology with crash rate as the metric.
The results are shown in Table 10.11.
TABLE 10.11: Safety Effects of Transverse Rumble Strips in California
Proportion Fatal +
Crash Rate
Site
CMF Injury (%) Change
Before After
Before After
1 2.5 0.4 0.16 67 0 -67
2 4.9 2.0 0.41 86 0 -86
3 4.2 1.0 0.24 75 100 +25
4 1.7 0.0 0.00 50 -- --
Average 3.32 0.85 0.26 69 33 -42
Before crash rates were based on 20 to 32 months of data; after crash rates used 10 to 31
months of data. The study did not use a control group to account for confounding factors.
However, the author notes that crashes on County roads have been increasing.
Owens (1967)
An evaluation of the safety impacts of transverse rumble strips at six rural, stopcontrolled
intersections in Minnesota was carried out by Owens (1967). The study used a
naïve before-after methodology with crash frequency as the metric. The sites were highspeed
intersections, with at least 1000 feet of unobstructed visibility on all approaches.
Traffic control devices conformed to the then current MUTCD, in addition to all
approaches having “STOP AHEAD” pavement markings.
The treatment consists of rumble strips placed in the following pattern:
• Four strips 25 ft long spaced 100 ft apart;
• Six strips 25 ft long spaced 50 ft apart; and
• One 50 ft long strip at the intersection.
Only two of the intersections had been installed such that at least one year of “after” data
was available (the remainder of the intersections were studied for approach speed, stop
sign compliance, etc.). The results of the crash analysis is shown in Table 10.12.
TABLE 10.12: Safety Impacts of Transverse Rumble Strips in Minnesota
Approach
Crashes/year CMF
Approach Intersection