Examination of the geometric design parameters contributing to heavy vehicle stability and rollover effects at roundabouts in high-speed areas

Examination of the geometric design parameters contributing to heavy vehicle stability and rollover effects at roundabouts in high-speed areas

Roundabouts in rural locations typically have high approach speeds and are often criticised for catastrophic incidents. This report reviews the literature on heavy vehicle rollovers at roundabouts, covering the most frequently cited papers. The study emphasised a comprehensive review of geometric features that contribute to the rollover of heavy vehicles in high-speed roundabouts, with a broad focus on studies from overseas.
A global comparison of roundabout design guidelines found that design standards in Australia, the UK, and the USA are more similar, while continental European countries favour smaller roundabout designs. The report described the fundamentals of roll stability, considering the rollover process's static and dynamic aspects. Techniques such as simulations, safety audits, data analysis, and direct observations were good for understanding the causes of truck rollovers; thus, many reviewed articles used one or more of these techniques.
Reviewed studies indicate that the speed of a truck has a substantial impact on the likelihood of a rollover accident occurring. Other factors contributing to rollover occurrence include smaller entry deflection, high visibility, no speed-reducing treatments, a considerable drop in circulating radius within the roundabout, sudden superelevation shifts, and higher kerbs or truck aprons. Application of globally accepted measures highlights that some of the geometric elements that can effectively be designed to slow down the speed, including advanced traffic control devices (such as signs, yield signs, pavement markings, and rumble strips), an extended splitter island, strategies to limit visibility to a safe stopping distance, and specific elements such as the deflection angle and circular island. Additionally, roundabouts sometimes equip their exit and approach curves with truck aprons to facilitate truck movement. The study further investigated recommendations for roundabout design in each state and territory. Thus, this study concludes that a supplementary roundabout design guideline should be developed for designing roundabouts in rural and high-speed areas to reduce unexpected truck crashes, including rollovers. In addition, this study recommended employing simulation modelling in future studies because it benefits redesigning existing roundabout alignments and developing new ones

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