Date of this Version
Roadside concrete barriers have been widely used to protect errant motorists from hitting roadside hazards or obstacles. Two concrete barrier profiles, vertical and safety-shape, have been used for this purpose. The safety-shape profile has been shown to produce excessive vehicle climbing which tends to increase rollover propensity. The vertical profile, on the other hand, does not cause vehicle climbing, but it does produce higher lateral forces which may produce higher injury levels.
The objective of this research is to investigate which barrier profile is the safest based on real-world vehicle crash data. The safest barrier profile is defined as the one that produces lower injury levels. Rollover propensity was also used as a second indicator of barrier performance since rollovers may also affect injury severity.
Eleven years of bridge-related crash data was collected from State maintained highways in the State of Iowa. Statistical procedures were used to conduct the data analysis which was sub-divided into two major tasks: rollover analysis and injury analysis.
It was found that rollovers are twice more likely to occur in crashes involving safety-shape barriers as compared to vertical barriers. It was also found that crashes that involved safety-shape barriers resulted in higher injury levels as compared to crashes that involved the vertical barriers.
Therefore, it is believed that the expanded use of vertical barriers would improve overall highway safety. However, this conclusion is based on limited data and a more comprehensive data set covering many more states besides Iowa is recommended for analysis in the future.
Advisor: Dean L. Sicking