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TECHBRIEF
This techbrief is an archived publication and may contain dated technical, contact, and link information
Publication Number:  FHWA-HRT-17-067    Date:  November 2017
Publication Number: FHWA-HRT-17-067
Date: November 2017

 

Safety Evaluation of Horizontal Curve Realignment on Rural Two-Lane Roads

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FHWA Publication No.: FHWA-HRT-17-067
FHWA Contact: Roya Amjadi, HRDS-20, (202) 493-3383, roya.amjadi@dot.gov

This document is a technical summary of the Federal Highway Administration report Safety Evaluation of Horizontal Curve Realignment on Rural Two-Lane Roads (HRT-17-066).

Objective

The Federal Highway Administration (FHWA) established the Development of Crash Modification Factors (DCMF) Program in 2012 to address highway safety research needs for evaluating new and innovative safety strategies (improvements) by developing reliable quantitative estimates of their effectiveness in reducing crashes. The ultimate goal of the DCMF Program is to save lives by identifying new safety strategies that effectively reduce crashes and promote those strategies for nationwide implementation by providing measures of their safety effectiveness and benefit. This study evaluated realignment of horizontal curves on rural two-lane roads based on a before–after evaluation. This realignment strategy is intended to reduce lane departure crashes, especially run-off-road crashes. This evaluation developed crash modification factors (CMFs) for this strategy using state-of-the-art before–after empirical Bayes (EB) methods and then compared the results with previously developed CMFs from cross-sectional studies. The data included 39 realigned locations from California, North Carolina, and Ohio, and 56 untreated reference curves.

Typically, researchers have based studies on the effect of horizontal curve radius on a cross-sectional analysis, where they compare the safety performance of curves of differing radii. This methodology typically allows for a large potential sample of curves because there is no need to know a conversion/installation date as in a before–after study. However, a before–after methodology is generally preferable to cross-sectional for evaluating the safety effect of an infrastructure modification.(1)

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