Evaluation of safety effectiveness of composite shoulders, wide unpaved shoulders, and wide paved shoulders in Kansas : [technical summary].

PDFTech ReportK-TRAN: KU-11-1Paved shouldersRoad shouldersWidthHighway safetyImprovementsBenefit cost analysisRural highwaysTwo lane highwaysKansasKansas. Dept. of Transportation. Bureau of Materials & ResearchZeng, HuanghuiSchrock, Steven D.Mulinazzi, Thomas E.University of Kansas. Dept. of Civil, Environmental and Architectural EngineeringNTL-HIGHWAY/ROAD TRANSPORTATION-DesignNTL-HIGHWAY/ROAD TRANSPORTATION-Construction and MaintenanceUS Transportation CollectionIncremental increases in paved shoulder widths have been studied and are shown in the Highway Safety Manual (HSM). While each incremental increase in shoulder width is beneficial, there is evidence that suggests the relationship between safety improvements and incremental increases in shoulder width may not be linear. It is possible that the net safety gains for wider shoulder increments are not as high as incremental benefits of the initial increments of shoulder width. Thus, a highway agency may have opportunities for greater system-wide safety benefits from paving longer roadway segments with a narrower shoulder rather than paving shorter roadway segments with a wider shoulder. This approach is tempered by consideration of long term degradation in shoulder width and slope over the life of a facility due to normal pavement maintenance activities. Practitioners must balance long-term sustainability, cost, expected operations and safety benefits of proposed improvements. For new and reconstruction projects, the cost of additional shoulder width is minimal compared to retrofitting an existing facility