Jedniuk, Andrew (2024) Heavy vehicle rollovers at roundabouts on high-speed roads. [USQ Project]
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Abstract
The Australian government has become increasingly concerned with road crashes resulting in serious injuries and fatalities, with the freight industry transporting nearly 225 trillion tonne-kilometres to support Australia’s economy their increased exposure on the road makes them vulnerable.
Heavy vehicles crashes are less frequent than other vehicle types. However, there is more chance that the result of a heavy vehicle crash will lead to a fatality or serious injury. The combination of a bus and heavy-vehicles suspension system with their high centre of gravity results in these vehicles being prone to instability issues often resulting in a rollover-crash.
Road authorities often adopt the use of roundabouts as a way of simplifying conflicts at intersections through the controlling of vehicle approach speeds and changing the potential crash types whilst reinforcing the reduction of vehicle speed through a positive reinforcement of vehicular priority.
The presence of a roundabout as a traffic control method generally improves road safety by way of generating a circular flow around a central island. This circulating movement, combined with high approach speed has the potential to cause vehicle instability as it navigates through the roundabout, especially for higher mass vehicles due to the higher centre of gravity and tendency for vehicular roll. A crash resulting from a vehicle rollover is responsible for about one third of the recorded fatalities on the road yet only occurs in around 3% of crashes.
This study examines the design parameters and geometric elements within existing roundabouts on high-speed roads, single-lane and dual-lane focusing primarily on roundabouts with single and duallane approaches with an approach speed of 80km/h or greater. This analysis assists road design authorities reduce the instances of heavy vehicle rollovers. The focus of this study was to assist in developing a supplementary set of Austroads guidelines suitable for roundabouts on high-speed roads.
The literature review explored the human and engineering factors that lead to rollover crashes, and reviewed the current Austroads Guide to Roundabout Design and comparing the differences outlined within the Australian state’s supplements.
The Austroads guides discuss that controlling the vehicles speed entering the roundabout as the most important geometric parameter that leads to vehicle safety, with a preference to reduce travel speeds gradually on approaches by introducing measures such as; successive reverse curves, rumble strips, regulatory speed reductions, flashing lights / advisory signs, localised treatments giving the impression of restrictions.
Most of the disagreement between the states in their supplements was how high-speed roundabout environments are treated and the inconsistency of the adoption of reverse curves on approach to the intersection.
Crash data was obtained from NSW, Queensland and Victoria between 2001 and 2023 to identify roundabout locations that had a history of heavy vehicle rollovers at sites with an operating speed of 80km/h or greater. The analysis of the results identified that rollover crashes at roundabouts on highspeed roads accounted for 0.005% of all recorded crashes. The three sites selected for analysis based on their crash history were:
• Blacktown Road, Richmond Road and George Street, Londondary NSW
• Bruce Highway, Mackay Ring Road and Statham Drive, Padget QLD
• Princes Highway, Geelong Road, Wests Road and Werribee Main Road, Werribee, Victoria
The three sites were digitized and geometric data such as circulating radii, entry curve, carriageway widths, pavement crossfalls and rates of rotation were extracted. A robust design review process compared the measured criteria against Austroads minimum requirements and analysed whether any discrepancy had the potential to lead to heavy vehicle rollover crashes.
It was noted that no single element appears to cause rollover crashes in the selected sites, but that the application of design standards was incompatible for the selected sites and that multiple deficiencies were often found within the same proximity, compounding the severity of the deficiency.
It was identified early that most of the deficiencies identified were based largely around the inappropriate selection of a design vehicle, either being insufficient or overly conservative which led towards encroachments of kerbs and islands and thus compounding issues such as circulating radii, entry and exit widths and the tendency for rollover due to increased speed of crossfall changes.
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| Item Type: | USQ Project |
|---|---|
| Item Status: | Live Archive |
| Faculty/School / Institute/Centre: | Current – Faculty of Health, Engineering and Sciences - School of Engineering (1 Jan 2022 -) |
| Supervisors: | Somasundaraswaran, Soma |
| Qualification: | Bachelor of Engineering (Honours) (Civil) |
| Date Deposited: | 08 Oct 2025 03:42 |
| Last Modified: | 08 Oct 2025 03:42 |
| Uncontrolled Keywords: | road crashes; heavy vehicles; roundabouts |
| URI: | https://sear.unisq.edu.au/id/eprint/53054 |
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