This study evaluated the feasibility of adding rumble strips to the left side of rural freeways in New Brunswick. A review of 940 collisions that occurred on Route 2 and Route 95 was supplemented with an analysis of 547 incidents that occurred on the Brun-Way owned and operated sections of Route 2 and Route 95. The study revealed that despite significantly more traffic travelling in the right lane, a larger number of ROR crashes occurred to the left side. Four Crash Modification Factors (CMF’s) ranging from 0.87 to 0.96 were developed in order to estimate the potential benefit of left side rumble strip installation. A left side specific CMF of 0.95 was developed for all crashes and a CMF of 0.93 was developed for Fatal and Injury (FI) crashes. A benefit-cost analysis revealed that the B/C ratio of the installation of left side rumble strips ranged from 7.9 to 9.4.