Exploring the transferability of crash modification factors: case studies on passing lanes and dual rumble strips on Ontario two-lane highways

The safety effects of design and other highway improvement options are specified through Crash Modification Factors (CMFs). CMFs for two low cost safety treatment measures -- passing lanes and dual application of center line and shoulder rumble strips -- are explored separately in this paper. Using data provided from previous studies conducted in the United States, and generalized linear modeling, the transferability of the US-based knowledge on safety effects of passing lanes and rumble strips for application in Ontario was explored. It was found that the safety effects were consistent for passing lanes in Michigan and Ontario and a Crash Modification Function was developed relating the CMF to length of passing lane for the combined data. The dual rumble strip effects were also reasonably consistent with results from a limited analysis of Ontario data and are recommended for application in the province.