01587601

Component

Generally, a crash modification factor (CMF) represents the overall safety performance of a specific treatment. Although many researchers have estimated the safety effects (i.e. 1 – CMF or crash reduction factor (CRF)) of specific treatments (or countermeasures) in reducing crashes, there is a lack of prior studies that explored the variation of CMFs. Thus, the main objectives of this study are 1) to estimate CMFs for the installation of different types of roadside barriers, and 2) to determine the changes of safety effects for different crash types and severities based on different vehicle, driver, weather and time of day information. Two observational before-after analyses (i.e. empirical Bayes (EB) and Full Bayes (FB) approaches) were utilized in this study to estimate CMFs. To consider the variation of safety effects based on different vehicle, driver, weather, and time of day information, the crashes were categorized based on vehicle size (passenger and heavy), driver age (young, middle, and old), weather condition (normal and rain), and time difference (day time and night time). The results show that the addition of roadside barriers is safety effective in reducing severe crashes for all types and run-off roadway (ROR) crashes. On the other hand, it was found that roadside barriers tend to increase all types of crashes for all severities. The results indicate that the treatment might increase the total number of crashes but it might be helpful in reducing injury and severe crashes. In this study, the variation of CMFs was determined for ROR crashes based on the different vehicle, driver, weather, and time information. The results show that guardrails is more safety effective in reducing injury and severe ROR crashes for middle and old age drivers than young age drivers. It was found that the CMFs for injury and severe ROR crashes were lower for heavy vehicles than passenger cars. It was also found that the safety effects of the treatment were higher for injury and severe ROR crashes in night time than day time. Lastly, the CMFs were lower for severe ROR crashes in rain condition than normal weather condition. Based on the findings from this study, it can be recommended to identify the safety effects of specific treatments for different crash types and severity levels with consideration of the different vehicle, driver, weather, and time of day. Also, the results show that there are no big differences between the estimated CMFs from the EB and FB methods.

This paper was sponsored by TRB committee AFB20 Standing Committee on Roadside Safety Design.

01584066

16-0678

English

21p

2016

Transportation Research Board 95th Annual Meeting

Web

Figures; Photos; References (46) ; Tables

Crash characteristics; Crash severity; Drivers; Guardrails; Highway safety; Roadside; Weather conditions

Highways; Safety and Human Factors; I83: Accidents and the Human Factor; I85: Safety Devices used in Transport Infrastructure

Transportation Research Board Annual Meeting 2016 Paper #16-0678

TRIS, TRB, ATRI

Jan 12 2016 4:26PM