Evaluation of Recent Traffic and Safety Initiatives, Volume II: Developing a Procedure for Evaluating the Need for Raised Medians

Raised medians are a safety measure often used on highways to improve safety, maintain good traffic flow, and beautify the area. In this study, an extensive literature review was conducted to determine the advantages and disadvantages of raised medians. Raised medians were also compared to other median alternatives, such as two-way left-turn lanes (TWLTL) and undivided highways. Raised medians were found to provide better safety benefits than the other median types. A TWLTL tends to be a compromise between the raised median and the undivided highway because of the improvement in traffic flow and full property access. A survey was conducted on a principle arterial that recently installed a raised median. It was found that although raised medians may be perceived as an inconvenience, they do not keep customers from visiting adjacent businesses. Many also realized the safety benefits of raised medians. A crash analysis was also conducted on four highways in the greater Salt Lake City area. Raised medians were found to reduce severe crashes and right angle crashes in mid-blocks, while rear-end crashes increased in mid-blocks. Crashes did not necessarily shift to intersections. Right angle crashes at intersections either decreased or stayed the same, and rear-end crashes either increased or stayed the same. Using the information from the literature review, survey and crash analysis, a procedure for determining when to install a raised median was formulated. The procedure considers crash history, pedestrians, traffic volume, delays, number of driveways per mile, midblock openings, and number of lanes. The procedure was applied to St. George Boulevard in St. George, Utah.