Evaluation of roadside barrier performance : a case study in Istanbul

Abstract

Roadside safety is an important problem for Turkey. Statistics show that 30% of all the fatal and injury accidents in Turkey happen at the roadsides. Roadside barriers are used to improve safety at locations where the roadsides are not safe by preventing vehicles from running off the road. However, because of their wrong use, roadside barriers have become one of the contributors of roadside safety problems in Turkey in the past years. Therefore, understanding the nature of barrier accidents is very important for identifying the problems and developing countermeasures. The main goal of this study is to analyze the performance level of roadside barriers, and the nature of barrier accidents in an urban environment, namely Istanbul. To achieve this goal, 307 accident reports that were collected from Istanbul Emniyet Müdürlüğü were analyzed. To check the accuracy and to improve the quality of the data, each accident was located in Google Earth and investigated one by one using accident descriptions, sketches, satellite images and site photos. Statistical analyses were performed with the collected data to develop relationships with the barrier performance and the accident characteristics. A black spot analysis was performed to identify the most dangerous locations. The analyses showed that the barriers in Istanbul did not perform as desired for 38.8% of the accidents. It was found that the fatality and injury rate for barrier accidents is two times higher than that of Turkish accident rate. It was shown that there is a significant relationship between the barrier performance and accident severity. It was found that the performance of weak post w-beam barriers is not adequate with an undesired performance rate of 63%. Barrier performance is found to be exceptionally low in freeways. It was found that barrier design at the gore areas and at the terminal points is especially problematic.