Study Details

Study Title: Evaluation of the Safety Effectiveness of Installing Roadside Barriers with Different Driver, Vehicle, Weather, and Time of Day Conditions

Authors: Park et. al.

Publication Date: JAN, 2016

Abstract: 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 difference between the estimated CMFs from the EB and FB methods.

Study Citation: Park, J., M. Abdel-Aty, and J. Lee. "Evaluation of the Safety Effectiveness of Installing Roadside Barriers with Different Driver, Vehicle, Weather, and Time of Day Conditions". Presented at the 95th Annual Meeting of the Transportation Research Board, Paper No. 16-0678, Washington, D.C., (2016).

Related Citations: Park, J., M. Abdel-Aty, and J. Lee. "Use of empirical and full Bayes before-after approaches to estimate the safety effects of roadside barriers with different crash conditions". Journal of Safety Research, Vol. 58, (2016) pp. 31-40.


CMFs Associated With This Study

Category: Roadside

Countermeasure: Install w-beam guardrail

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
1.06 -6 4 Stars All All Principal Arterial Other Freeways and Expressways Not specified
0.99 1 4 Stars All Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.84 16 4 Stars All Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
1.01 -1 4 Stars Run off road All Principal Arterial Other Freeways and Expressways Not specified
0.89 11 4 Stars Run off road Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.74 26 3 Stars Run off road Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
1.15 -15 4 Stars Run off road,Other All Principal Arterial Other Freeways and Expressways Not specified
0.98 2 4 Stars Run off road,Other Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.81 19 3 Stars Run off road,Other Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
0.93 7 3 Stars Run off road,Other All Principal Arterial Other Freeways and Expressways Not specified
0.75 25 3 Stars Run off road,Other Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.65 35 3 Stars Run off road,Other Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
1.12 -12 3 Stars Run off road,Other All Principal Arterial Other Freeways and Expressways Not specified
1.11 -11 3 Stars Run off road,Other Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.95 5 3 Stars Run off road,Other Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
1.05 -5 3 Stars Run off road,Other All Principal Arterial Other Freeways and Expressways Not specified
0.85 15 3 Stars Run off road,Other Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.7 30 3 Stars Run off road,Other Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
0.93 7 3 Stars Run off road,Other All Principal Arterial Other Freeways and Expressways Not specified
0.8 20 3 Stars Run off road,Other Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.58 42 3 Stars Run off road,Other Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
0.95 5 4 Stars Dry weather,Run off road All Principal Arterial Other Freeways and Expressways Not specified
0.87 13 3 Stars Dry weather,Run off road Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.79 21 3 Stars Dry weather,Run off road Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
1.12 -12 3 Stars Run off road,Wet road All Principal Arterial Other Freeways and Expressways Not specified
0.96 4 3 Stars Run off road,Wet road Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.75 25 3 Stars Run off road,Wet road Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
1.05 -5 4 Stars Day time,Run off road All Principal Arterial Other Freeways and Expressways Not specified
1.01 -1 3 Stars Day time,Run off road Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.89 11 3 Stars Day time,Run off road Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
0.98 2 3 Stars Nighttime,Run off road All Principal Arterial Other Freeways and Expressways Not specified
0.73 27 3 Stars Nighttime,Run off road Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.53 47 3 Stars Nighttime,Run off road Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified

Countermeasure: Install w-beam guardrail and concrete barrier

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
1.01 -1 4 Stars All All Principal Arterial Other Freeways and Expressways Not specified
0.94 6 4 Stars All Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.82 18 4 Stars All Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
0.93 7 4 Stars Run off road All Principal Arterial Other Freeways and Expressways Not specified
0.84 16 4 Stars Run off road Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.73 27 4 Stars Run off road Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
1.03 -3 4 Stars Run off road,Other All Principal Arterial Other Freeways and Expressways Not specified
0.92 8 4 Stars Run off road,Other Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.81 19 4 Stars Run off road,Other Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
0.9 10 4 Stars Run off road,Other All Principal Arterial Other Freeways and Expressways Not specified
0.72 28 4 Stars Run off road,Other Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.66 34 3 Stars Run off road,Other Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
1.06 -6 3 Stars Run off road,Other All Principal Arterial Other Freeways and Expressways Not specified
1.06 -6 3 Stars Run off road,Other Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.91 9 3 Stars Run off road,Other Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
0.93 7 4 Stars Run off road,Other All Principal Arterial Other Freeways and Expressways Not specified
0.79 21 4 Stars Run off road,Other Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.69 31 4 Stars Run off road,Other Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
0.91 9 3 Stars Run off road,Other All Principal Arterial Other Freeways and Expressways Not specified
0.8 20 3 Stars Run off road,Other Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.62 38 3 Stars Run off road,Other Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
0.92 8 4 Stars Dry weather,Run off road All Principal Arterial Other Freeways and Expressways Not specified
0.82 18 4 Stars Dry weather,Run off road Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.76 24 4 Stars Dry weather,Run off road Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
0.92 8 4 Stars Run off road,Wet road All Principal Arterial Other Freeways and Expressways Not specified
0.9 10 4 Stars Run off road,Wet road Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.75 25 3 Stars Run off road,Wet road Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
0.96 4 4 Stars Day time,Run off road All Principal Arterial Other Freeways and Expressways Not specified
0.94 6 4 Stars Day time,Run off road Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.84 16 4 Stars Day time,Run off road Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified
0.92 8 4 Stars Nighttime,Run off road All Principal Arterial Other Freeways and Expressways Not specified
0.71 29 4 Stars Nighttime,Run off road Fatal,Serious injury,Minor injury Principal Arterial Other Freeways and Expressways Not specified
0.6 40 3 Stars Nighttime,Run off road Fatal,Serious injury Principal Arterial Other Freeways and Expressways Not specified

The information contained in the Crash Modification Factors (CMF) Clearinghouse is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in the CMF Clearinghouse. The information contained in the CMF Clearinghouse does not constitute a standard, specification, or regulation, nor is it a substitute for sound engineering judgment.