Analysis of road crashes at roundabouts in Toowoomba

Richardson, Megan (2016) Analysis of road crashes at roundabouts in Toowoomba. [USQ Project]

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Every year, road crashes cost Australia an estimated $27 billion in additional to the devastating social impacts these crashes have on the community. Toowoomba’s road network has a significant number of roundabouts with approximately one roundabout for every two signalised intersections; with more roundabouts being constructed every year. The aim of this investigation is to evaluate the safety performance at roundabouts in Toowoomba to re-examine the contribution that geometric features of the poorer performing roundabouts have in severity and frequency of road crashes.

A combination of two road safety methodologies were utilised to rank the top 10 worst performing roundabouts in Toowoomba. By combining the two methods more variables were able to be considered in the ranking process; the Critical Crash Rate method considered crashes with respect to traffic volume and the Relative Severity Index method used costs per crash type considering the costs of a crash based on a potential severity. The methods were subsequently combined using scores and weighting factors.

The crash investigations, road safety audits and geometric property investigations conducted at the subject roundabouts identified that the most significant crash contributory factors were high entry speeds and reduced sight distance upon approach to the roundabout. The observed high entry speeds were most commonly associated with entry path radii that were too large as well as inadequate deflection through the roundabout. Insufficient sight distance due to vegetation on the corners of roundabouts was a common issue observed at the subject roundabouts and there were significant numbers of infrangible objects such as electricity/light poles and trees within the clearance zone of the roundabouts.

Remedial measures such as reducing entry path radii, radius of deflection and entry widths to limit entry speed, removal of vegetation on corners of roundabouts to improve sight distance, re-application of faded line marking and symbols to improve driver path through the roundabout and removing/relocating power/light poles located within the clearance zone to reduce the frequency and severity of hit object crashes are recommended in order to improve safety at the subject roundabouts.

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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Honours) Major Civil Engineering project
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 - 31 Dec 2021)
Supervisors: Somasundaraswaran, Soma
Date Deposited: 21 Jul 2017 04:38
Last Modified: 21 Jul 2017 04:38
Uncontrolled Keywords: road crashes; road network; Toowoomba; geometric property; crash investigations; roundabouts; signalised intersections
Fields of Research (2008): 09 Engineering > 0905 Civil Engineering > 090502 Construction Engineering
Fields of Research (2020): 40 ENGINEERING > 4005 Civil engineering > 400504 Construction engineering

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