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:
  Benefit Cost Analysis Highway Safety Improvements Paved Shoulders Road Shoulders Rural Highways Two Lane Highways Width
• 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.
  
  
• Format:
  PDF
• Funding:
  C1892
• Collection(s):
  University Transportation Centers US Transportation Collection
• Main Document Checksum:
  urn:sha256:4e5786fe4f9d3edbd771463a33f928259d8f3dcd2e74ae79d2ab2c73b98911eb
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/25822/dot_25822_DS1.pdf
• File Type:
  [PDF - 1.50 MB ]