Safety Study

The safety aspect of wider lines will be addressed using a dual approach. The major approach will consist of a crash surrogate study. The crash surrogate study will focus on the operational aspects (e.g., change in deceleration profiles approaching and negotiating the curve, change in mean speed, change in speed variability, mean lateral placement, and lateral placement variability) of vehicles when negotiating horizontal curves on two-lane highways that are marked with 4-inch and 6-inch pavement marking edgelines.

The second approach is aimed at supplementing the operational study; it will include a multi-State retrospective crash study focusing on 4-inch lines versus 6-inch lines. This will include a national survey of wider marking practices to identify States that know where and when they have installed wider markings. Crash data from those States will be pooled to conduct a robust statistical analysis of the safety impacts of wider markings.

The dual safety approach is expected to provide a robust analysis that will yield conclusive findings related to the effectiveness of wider lines. In other words, the dual approach, while tougher to implement, was selected because it maximizes the likelihood of conclusive results.

The original intent was to conduct identical crash surrogate studies in both Alaska and Tennessee. While the advantage of having study sites in two different regions is appealing, there are significant disadvantages to weigh against the potential gains. A major issue is whether sufficient and accurate data could be collected in Alaska. Both daytime and nighttime study hours of data collection will be needed. However, during the summer time in Alaska, when the edgelines are not covered by snow, the number of nighttime hours to collect data is severely reduced. Additionally, Alaska has a limited roadway inventory to locate study sections, and therefore, the costs of travel, not only to Alaska but between study sites, is high compared to Tennessee. By focusing the attention of the crash surrogate study to Tennessee, the research team would able to strengthen the data collection plan by adding comparison study sites and increasing the amount of data collected at each site. The crash surrogate study will be revised in early 2007 to gather data in both Alaska and Tennessee; however, the revised plan may not include identical crash surrogate studies. For instance, two possible options would be to: (1) reduce the effort in Tennessee and add a similar study approach in Alaska, except focus on daytime, or (2) add an instrumented vehicle study approach.

National Wider Marking Survey
Results of Original Survey
Follow-up Results

Update on Crash Surrogate Study

Update on Multi-State Retrospective Crash Study

Durability Study

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