This paper describes the results of a comprehensive before and after study to evaluate the safety impacts associated with the application of shoulder and centerline rumble strips on British Columbia (BC) Highways. Data was collected for three distinct groups of sites, including a treatment group, comparison groups and reference groups. The treatment group included 47sites which belong to two highway classes (an undivided, rural 2-lane arterial RAU2 and a divided, rural 4-lane freeway RFD4). A total of 225 siteswere used to establish comparison groups for the various treatments sites, based on the implementation year for the treatment site and the highway class. The comparison groups were used to correct for the confounding factors of history and maturation. Six different reference groups were used, which correspond to the two highway classes (RAU2 and RFD4) and three time periods (2000-2002, 2001-2003, and 2002-2004). The collision prediction models (CPMs) developed from the reference groups were used to correct for the regression to the mean and to account for the changes in traffic volumes in the before and after period. Overall, the results showed that shoulder and centerline rumble strips can significantly reduce severe collisions and specific collision types. The results show that the installation of rumble strips reduced all injury collisions by a statistically significant18.0%. The results also indicate that shoulder rumble strips reduced off-road right collisions by a statistically significant 22.5%. For centerlinerumble strips (RAU2 sites), the results showed a statistically significant reduction of 29.3% in off-road left and head-on collisions. RAU2 sites that had both centerline and shoulder rumble strips installed showed a statistically significant reduction of 21.4% in off-road right, off-road left and head-on collisions combined.
Abstract