Study Details

Study Title: Developing Crash Modification Factors for Guardrails, Utility Poles, and Side-Slope Improvements

Authors: Avelar et al.

Publication Date:AUG, 2021

Abstract: Through this project, researchers evaluated the safety effects of guardrails, utility poles, and side slopes using safety data from Indiana and Pennsylvania. Safety evaluations in this project focused on total, fatal-and-injury, and roadway-departure crash risk. Crash modification factors (CMFs) and benefit–cost (B/C) ratios were developed for the safety improvements (guardrails, utility poles, and side slopes) of interest. The CMFs for protecting utility poles with guardrails were not statistically significant for total and roadway-departure crashes (CMF values were 0.89 and 1.52, depending on how close the utility poles were to the roadway). The CMFs for fatal-and-injury crashes were statistically significant (CMFs of 0.524 and 0.433, depending on pole proximity to the roadway). Results for CMFs developed for pole removal in terms of fatal-and-injury crashes indicated a statistically significant CMF of 0.656. For pole relocation, this evaluation found a statistically significant CMF of 0.866 on total crashes. Finally, estimated CMFs for side-slope flattening indicated reductions in total and roadway-departure crashes. The statistically significant CMFs varied between 0.923 and 0.936 for total crashes and between 0.784 and 0.951 for roadway-departure crashes, depending on the initial and final flattened-slope values. The economic evaluation of guardrails indicated that guardrail implementations are economically viable when protecting roadside utility poles (a B/C ratio of 1.28 or 1.48). The economic evaluation of pole removal or relocation indicated that this strategy is economically viable when not considering the acquisition of new right-of-way (a B/C ratio of 6.73).

Study Citation: Avelar, R., K. Dixon, S. Ashraf, and AS. Jhamb. "Developing Crash Modification Factors for Guardrails, Utility Poles, and Side-Slope Improvements." Report No. FHWA-HRT-21-075. Federal Highway Administration. McLean, Virginia. (August 2021).

Related Citations: Tech Brief. "Developing Crash Modification Factors for Guardrails, Utility Poles, and Side-Slope Improvements." Report No. FHWA-HRT-21-076. Federal Highway Administration. McLean, Virginia.


CMFs Associated With This Study

Category: Roadside

Countermeasure: Flatten side slopes

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.869913.013 StarsOtherAllAllRural
0.92237.773 StarsAllAllAllRural
0.688631.143 StarsAllK,A,B,CAllRural
0.784421.563 StarsOtherAllAllRural
0.9366.43 StarsAllAllAllRural
0.721627.843 StarsAllK,A,B,CAllRural
0.82217.83 StarsOtherAllAllRural
1.0153-1.533 StarsAllAllAllRural
0.743225.683 StarsAllK,A,B,CAllRural
0.95094.913 StarsOtherAllAllRural
0.97882.123 StarsAllAllAllRural
0.744325.573 StarsAllK,A,B,CAllRural

Countermeasure: Protect Side Slopes with Guardrails

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
1.044-4.43 StarsOtherAllAllRural
0.9752.53 StarsAllAllAllRural
0.52447.63 StarsAllK,A,B,CAllRural
1.046-4.63 StarsOtherAllAllRural
1.044-4.43 StarsAllAllAllRural
0.64835.23 StarsAllK,A,B,CAllRural
0.9336.73 StarsOtherAllAllRural
0.9643 StarsAllAllAllRural
0.60739.33 StarsAllK,A,B,CAllRural

Countermeasure: Protect Utility Poles with Guardrails

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
1.38-383 StarsOtherAllAllRural
0.89210.83 StarsAllAllAllRural
0.523947.613 StarsAllK,A,B,CAllRural
0.817218.283 StarsOtherAllAllRural
1.52-523 StarsAllAllAllRural
0.43356.73 StarsAllAllAllRural

Countermeasure: Remove/Relocate Utility Poles

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
1.3375-33.753 StarsOtherAllAllRural
0.865613.443 StarsAllAllAllRural
0.98921.083 StarsAllK,A,B,CAllRural
0.90079.933 StarsOtherAllAllRural
0.865613.443 StarsAllAllAllRural
0.655534.453 StarsAllK,A,B,CAllRural