Synthesis of Safety for Traffic Operations - Transports Canada

Pavement Markings
Hall (1987)
Hall (1987) investigated the use of eight-inch wide edgelines on rural, non-Interstate
highways in New Mexico as a means of reducing run-off-the-road crashes. Sites were
selected for treatment because they had a high rate of ROR crashes, as determined by the
rate quality control technique. A comparison group was used in the analysis; this group
was also considered to have a high rate of ROR crashes, and was chosen to account for
regression-to-the-mean effects. A summary of the sites used in the analysis is found in
Table 5.6.
TABLE 5.6: Sites used in the Assessment of Wide Edge Lines
Site Type*
Number Length of road Before Period After Period
of Sites (miles) (months) (months)
Treatment 1 19 101 41 17
Treatment 2 12 76 52 5
Control 38 353 41 to 52** 5 to 17
* Treatment 1 and Treatment 2 sites are different groups of sites with the same treatment applied.
** The analysis periods vary because some of the control sites were converted to Treatment 2 sites part
way through the evaluation.
The ROR crash rates for Treatment Group 1 experienced a 10% decrease while the
control group experienced a 16% decrease. The ROR crash rates for Treatment Group 2
experienced a 17% decrease while the control group experienced a 24% decrease. Hall
performed some additional analysis on night-time, curve-related, and opposite-direction
crashes to attempt to determine if the wide edge lines were more (or less) effective for
certain conditions – there were no significant findings.
Hall recommends against the use of wide edgelines on rural roads in New Mexico based
on no evidence suggesting a safety benefit. In fact, the results suggest that the wide edge
lines actually have a detrimental impact in safety. If regression-to-the-mean is properly
accounted for, and the edge lines truly had no effect on safety performance, then one
would expect the reduction in the crash rate for the treatment groups to be the same as
that experienced by the control group. Both groups experienced a decline in crash rate,
likely due to RTTM effects, however, the treatment groups experienced a smaller decline
and this suggests that the RTTM was offset by an increase in collision rate.
Lee et al (1997)
A study to examine the relationship between night-time crashes and the retro-reflectivity
of longitudinal pavement markings was conducted by Lee et al (1997). The study was
undertaken in Michigan and included 46 test sites that constituted 1875 kms of roadway.
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