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Case-control and cross-sectional methods for estimating crash modification factors: comparisons from roadway lighting
1Vanasse Hangen Brustlin, Inc. 333 Fayetteville St, Suite 1450, Raleigh, NC 27601, USA. fgross@vhb.com
Problem:
While observational before-after studies are considered the industry standard for developing crash modification factors (CMFs), there are practical limitations that may preclude their use in highway safety analysis. There is a need to explore alternative methods for estimating CMFs.
Method:
This paper employs case-control and cross-sectional analyses to estimate CMFs for fixed roadway lighting and the allocation of lane and shoulder widths.
Results:
Based on the case-control method, the CMF for intersection lighting is 0.886, while the cross-sectional study indicates a CMF of 0.881. The CMFs developed for lane and shoulder widths are also similar when comparing the two methods.
Conclusions:
This paper suggests that case-control and cross-sectional studies produce consistent results if care is taken in the study design and model development.
Impact On Industry:
Case-control and cross-sectional studies may provide a viable alternative to estimate CMFs when a before-after study is impractical due to data restrictions.
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