Roadside design assessment in an urban, low-density environment in the Gulf Cooperation Council region

Abstract

Objectives: Proper roadside design is crucial in order to mitigate the consequences associated with single-vehicle runoff road (SVROR) crashes. However, the Gulf Cooperation Council (GCC) region lacks in-depth, detailed information on its roadside design status. Hence, there is a need for an in-service evaluation of roadside design in the GCC region. The objective of this study is to assess the existing roadside design in a medium-sized, low-density city in the United Arab Emirates (UAE). Methods: A multiyear crash database was used to identify 116 locations where SVROR injury crashes occurred between 2013 and 2016 in the city of Al Ain in the UAE. Visits to these locations were made in order to assess their roadside design. Subsequently, the collected data were analyzed. Roadside design was classified based on whether or not it deviated from roadside design guidelines. The guidelines adopted as a benchmark were those contained in the 2012 Abu Dhabi Department of Transport Roadside Design Guide (RDG) and/or those in the 2011 American Association of State Highway and Transportation Officials (AASHTO) RDG. It is worth stressing that local guidelines are heavily based on the 2011 AASHTO RDG. Results: The study found that almost one quarter of all SVROR crashes resulted in injuries. The study also found that a staggering 80.17% of the SVROR injury crashes investigated occurred at locations where roadside design deviated from the benchmark. Lack of an adequate clear zone was the main cause of noncompliant locations. Most SVROR injury crash locations containing roadside design with deviations from the benchmark were located on roads with posted speed limits of 100 kph or higher. Light poles, trees, curbs, and barriers were the most harmful objects most often struck, and tree collisions accounted for the highest number of severe crashes. Ninety-four and 86% of all studied locations containing light poles and trees, respectively, were found to be noncompliant with the benchmark. Twenty-eight percent of all SVROR injury crashes involved a rollover. All rollovers were preceded by a collision with a tree, pole, guardrail, or curb. Forty-four percent of all rollover crashes resulted in severe injuries. Conclusions: Significant revision of the existing roadside design not only in the area studied but throughout the UAE is recommended. The authors propose measures that may be useful in making roadside design in the area studied better align with the benchmark requirements.

Roadside Fixed-Object Collisions, Barrier Performance, and Fatal Injuries in Single-Vehicle, Run-Off-Road Crashes

“…If, and only if, none of these design priorities can be implemented, shielding should be considered. Unfortunately, research has shown that roadside design compliance has been lacking [7].…”

“…SVROR, fixed-object crashes account for a large portion of all SVROR-injury crashes [1][2][3][4][5][6]. Fixed objects such as poles, trees, and barriers have been found to be the most harmful object struck by errant vehicles [1,7].…”

Benchmark Compliance Evaluation of the Roadside Design in an Urban, High-Density Area

“…Table 2 shows that almost 22% of all SVROR-injury crashes involved severe injuries while a staggering 89.5% (see number in bold) occurred at locations found to be non-compliant. This indicates that meeting roadside design compliance may be slightly more challenging in a dense, urban area as compared to areas that are not densely populated [33]. This may be attributed to more limited right-of-way (ROW) availability in densely populated areas and may be an indication of the need for research related to the identification of a more practical, minimum-recommended-CZ-distance policy for urban areas.…”