Roadway departure crashes account for half of all fatalities every year, more than 18,000, with more than 5,000 fatalities resulting from head-on crashes. These crashes occur primarily on undivided, high-speed, rural roads with vehicles traveling in opposite directions, often separated only by a center line pavement marking and possibly a rumble strip. NCHRP Project 17-66 research was published in NCHRP Research Report 995: Guidelines for Treatments to Mitigate Opposite Direction Crashes, which provided guidance for selecting appropriate countermeasures for opposite-direction crashes. One countermeasure, center line buffer areas, was found to significantly reduce fatalities and is being used in locations around the country. NCHRP Project 17-66 developed crash modification factors (CMFs) for center line buffer areas (2 ft, 4 ft, and 6 ft in width). However, challenges arise with the implementation of center line buffer areas when determining where the extra pavement area will come from. In cases where the roadway cannot be widened to accommodate the center line buffer area, a practitioner or designer must decide between narrowing lanes or shoulders. Guidance is needed to inform designers on whether it will be a safety benefit or detriment to narrow lanes or shoulders to accommodate a center line buffer area. Which safety benefit, center line buffer areas, wider lanes, or wider shoulders, will be the governing factor and drive the decision on where to allocate the additional pavement area?

The objective of this research project is to develop recommendations on where additional pavement areas for center line buffer areas will come from. The research project shall determine the tipping point on whether the safety benefit of center line buffer areas is greater than the safety benefit of wider lanes or shoulders.