Development of Crash Modification Factors and Functions for Widening Shoulder Width on Rural Two-Lane Roadways

This study assesses the safety effectiveness of widening shoulder width in reducing crashes on roadway segments. Generally, a crash modification factor (CMF) represents the overall safety performance of specific treatment in a single value. Although many researchers have estimated CMFs for various treatments (or countermeasures), there is a lack of prior studies that explored the variation of CMFs with different roadway characteristics among treated sites. Therefore, the study develops crash modification functions (CMFunctions) to determine the relationship between safety effects and different roadway characteristics among treated sites. This study first evaluates the CMFs for widening shoulder width using the observational before-after with empirical Bayes (EB) method to check overall safety effects. Secondly, the CMFs were calculated for each treated site based on different roadway characteristics such as original shoulder width of treated sites in before period and actual widened width. Lastly, the variation of CMFs was determined through developing CMFunctions. Crash and roadway characteristic data was collected for rural two-lane roadways in Florida, and the Florida-specific full SPFs for different crash types and severity levels were developed and used for the observational before-after with EB estimation.


  • English

Media Info

  • Media Type: Digital/other
  • Features: References; Tables;
  • Pagination: 15p
  • Monograph Title: Proceedings of the 25th World Road Congress - Seoul 2015: Roads and Mobility - Creating New Value from Transport

Subject/Index Terms

Filing Info

  • Accession Number: 01676789
  • Record Type: Publication
  • ISBN: 9782840604235
  • Report/Paper Numbers: 0216
  • Files: TRIS
  • Created Date: Jul 10 2018 2:40PM