Evaluation of safety effectiveness of composite shoulders, wide unpaved shoulders, and wide paved shoulders in Kansas.

Details

• Creators:
  Zeng, Huanghui ; Schrock, Steven D. ; Mulinazzi, Thomas E.
• Corporate Creators:
  University of Kansas. Dept. of Civil, Environmental and Architectural Engineering
• Corporate Contributors:
  Kansas State University. Transportation Center ; United States. Dept. of Transportation. Research and Innovative Technology Administration
• Subject/TRT Terms:
  • Paved shoulders
  • Road shoulders
  • Width
  • Highway safety
  • Improvements
  • Benefit cost analysis
  • Rural highways
  • Two lane highways
• Publication/ Report Number:
  K-TRAN: KU-11-1
• Resource Type:
  Tech Report
• Geographical Coverage:
  Kansas
• Corporate Publisher:
  Kansas. Dept. of Transportation. Bureau of Materials & Research
• NTL Classification:
  NTL-HIGHWAY/ROAD TRANSPORTATION-Design ; NTL-HIGHWAY/ROAD TRANSPORTATION-Construction and Maintenance
• Abstract:
  Incremental increases in paved shoulder widths have been studied and are shown in the Highway Safety Manual. 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. Determining ; the benefits of various shoulder improvement approaches fits within the Kansas Department of Transportation’s (KDOT) ; “Practical Improvements” approach to maximize benefits relative to the construction and maintenance costs required. ; Among the 8,300 miles of rural two-lane highways in Kansas, approximately 25 percent of them are equipped with ; composite shoulders consisting of three feet of pavement with the remainder aggregate or turf. Their safety effectiveness was ; studied using the Empirical Bayes (EB) approach and the cross-sectional approach. Three developed Safety Performance ; Functions (SPFs) were used to create Kansas-specific Crash Modification Factors (CMFs) for composite shoulders compared with ; segments with no or unpaved shoulders. It was found that upgrading narrow unpaved shoulders to composite shoulders can reduce ; shoulder related crashes by up to 61 percent and fatal and injury crashes by 31 percent. It was also found that wide paved shoulders ; can provide more safety benefit than composite shoulders, and wide unpaved shoulders can provide slightly less safety benefit than ; composite shoulders. Based on these results, 20-year projections were developed projecting the safety effectiveness that can be ; achieved through implementing these safety improvements.
  More +
• Format:
  PDF
• Funding:
  C1892
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/25822/dot_25822_DS1.pdf
• File Type:
  [PDF - 1.50 MB]
• Collection(s):
  University Transportation Centers ; US Transportation Collection
• Main Document Checksum:
  urn:sha-512:7e7c81b64e37950490f96dfb0bfd1a47a0bff7c62a310e56bb3482d0d66dad3d3ade69e893c441bee5f6a62a9b0bf0b97db5d35a72b463a81bc0a6d6e4902a12