This study evaluated 63 rolled-in continuous shoulder rumble strips (CSRS) in Illinois and 28 CSRS in California. Using the Illinois data, a before-and-after evaluation with yoked comparison sites was performed first. The average safety effect of CSRS was estimated to be an 18.4 percent reduction in the number of single-vehicle run-off-road crashes, with a standard deviation of 6.8 percent. Next, the Illinois data were used in a before-and-after evaluation with a comparison group. The average safety effect of CSRS on rural freeways was estimated to be a reduction of single-vehicle run-off-road crashes by 21.1 percent, with a standard deviation of 10.2 percent. A before-and-after evaluation with a comparison group was used for California. The average safety effect of CSRS was estimated to be a 7.3 percent reduction in the number of single-vehicle run-off-road crashes, with a standard deviation of 13.4 percent. Although sophisticated cost-benefit analyses were not conducted, it was estimated that one single-vehicle run-off-road crash (at an average cost of $62,200) could be prevented every three years for an investment of $217 to install one km of CSRS.