Evaluating the Safety Effectiveness of Regulatory Headlight Signs in Wyoming PDF Download

Author: Md. Hamidur Rahman
Publisher:
ISBN: 9781369761856
Category : Roads
Languages : en
Pages : 176

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Book Description
To achieve better traffic management, transportation agencies implement a variety of traffic safety countermeasures in their roadway system. Regulatory headlight sign is a countermeasure which can be implemented on roadway sections with challenging geometrical characteristics to require drivers to turn on their headlights manually. Several studies showed that Daytime Running Lights (DRL) technology reduces certain types of multi-vehicle daytime crashes. Elvik (1996) conducted a meta-analysis using previous 17 studies that estimated safety effectiveness of DRL and concluded that DRL technology reduces certain types of daytime multi-vehicle crashes (head-on and opposite sideswipe crashes) by 10- to-15%. It is recognized that the overall safety effectiveness of DRL for different road users is still up for debate. Assuming that instructions given on a headlight sign will be observed and obeyed by motor vehicle drivers, these signs may help in increasing vehicle conspicuity and detectability. Headlights may help drivers maintaining appropriate lane position and proper gap with ambient traffic and hence improve safety. This study evaluated the safety efficacy of regulatory headlight signs by calibrating Crash Modification Factors (CMFs) on rural two-way two-lane mountainous roadway sections in Wyoming using various case-control, and observational before-after studies. Research related to the Crash Modification Factor estimation of regulatory headlight signs is hard to come by. The Federal Highway Administration (FHWA) launched an online site named “Crash Modification Factor Clearing House” in a bid to compile CMFs reported by various researchers in the transportation field. The Highway Safety Manual (HSM 2010) also provides CMF values for a number of countermeasures. The HSM also provides detailed steps on how to calibrate quality CMFs. The CMF for regulatory headlight 6zsign does not exist in the FHWA CMF Clearinghouse and the Highway Safety Manual suggesting scarcity of research on this countermeasure. This study will augment the understanding of the role of regulatory headlight signs on two-way two-lane mountainous roadway sections. There are seven regulatory headlight sign sections in Wyoming’s two-way two-lane roadway system. Daytime Running Light can be enforced in two forms; as a mandatory technological feature equipped in vehicles that turn on headlights with the start of the ignition, or as a behavioral measure that requires drivers to turn on headlights of their vehicles manually wherever they enter such regulatory headlight sign sections on a roadway. The main focus of this study was the manual headlight operation with taking into consideration the market penetration of the automatic DRL technology as well as drivers’ compliance with the headlight sign countermeasure. Three methods were attempted to achieve the goal of this research. In the case-control method, simple odds and odds ratios were utilized to quantify how strongly the presence of DRL is associated with the existence of headlight signs for crashes in two-way two-lane highways. Cross-sectional data for crash frequency and factors affecting crash frequency of a segment from both headlights sign sections and reference sections were also used in a cross-sectional design. In the before-after with EB study, only three sections; WY220 MP 88-102, WY59 MP 76-101, and WY28 MP 24.408-68.219 were used in a 3-year before and 2-year after study due to data limitation. Wyoming-specific simple Safety Performance Functions (SPFs) and full SPFs were used to estimate safety effectiveness of regulatory headlight signs for different crash types. Odds ratio determined from case-control analysis for total crash type indicates no significant effect of the presence of DRL equipped vehicles on the roadway sections with or without regulatory headlight signs. Similar conclusion was obtained for target crashes, i.e., head- on and opposite sideswipe crashes. It should be noted that both findings were not statistically significant. Results from the cross-sectional study show that Crash Modification Factor of regulatory headlight sign is less than 1 in all crash types considered except target crash type indicating safety benefit with the maximum value of 1.20 observed in target crash type and the minimum value of 0.5233 observed in fatal plus injury crash type, respectively. None of the results are statistically significant at 95% confidence level. Results from the before-after with EB study using both simple SPF and full SPF show that installing regulatory headlight sign on rural two-way two-lane mountainous roadway sections results in unreasonable safety effectiveness for total, target, and fatal plus injury crash types. Both results are over-estimating the safety effects of headlight signs and cannot be accepted from an engineering perspective. There might be several reasons behind this high safety estimate including some other unobserved treatments that were not considered in the analysis. Moreover, the limited number of treated sites could be another reason; only three sites were utilized in the study.