A Review of Crash Modification Factor (CMF) Estimation



Mohammad Nour Al-Marafi1, *, Kathirgamalingam Somasundaraswaran 2
1 School of Civil Engineering, Tafila Technical University, Tafila, Jordan
2 School of Civil Engineering and Surveying, University of Southern Queensland, Queensland, Australia

Abstract

Background

Road authorities and road safety experts are involved with estimating the expected outcomes originating from road safety treatments. Information derived from proposed treatments enables planners to make comparisons between the expected savings from crash reductions and associated treatment costs.

Aim

The purpose of this review is to provide direction to agencies and practitioners interested in estimating safety effectiveness.

Methods

Specifically, this study discusses the main methods for developing CMFs, including an overview of each method, data considerations, and their strengths and weaknesses. It also discusses the techniques of estimating combined CMFs resulting from multiple safety treatments.

Results

The review showed that observational Before–After (BA) studies with the Empirical Bayes (EB) and Full Bayes (FB) approaches provides enhanced consistency and precision for the estimated safety effectiveness. Alternatively, the cross-sectional method can be adopted in cases where observational BA studies are not practical due to data restrictions. Five additional techniques for estimating combined CMFs are also reviewed.

Conclusion

The study notes that while there has been substantial research in the broad area, very few studies have reported comparative methods of combined CMF estimation. Future research directions and research gaps are also highlighted in this review.

Keywords: Safety, Safety effectiveness, Evaluation, Crash modification factors, Countermeasures, Highway Safety Manual.


Abstract Information


Identifiers and Pagination:

Year: 2023
Volume: 17
DOI: 10.2174/18744478-v17-e230120-2022-38

Article History:

Electronic publication date: 20/1/2023
Collection year: 2023

© 2023 Al-Marafi and Somasundaraswaran.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


* Address correspondence to this author at the School of Civil Engineering, Tafila Technical University, Tafila, Jordan; E-mail: moh.marafi89@gmail.com