Evaluation of Signalisation as a Treatment for Roundabouts

Towers, Haley (2021) Evaluation of Signalisation as a Treatment for Roundabouts. [USQ Project]

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TOWERS Haley_dissertation_Redacted.pdf

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Roundabouts are a form of intersection treatment that are known to improve traffic efficiencies and safety for road users. These recognised benefits have led to many signalised intersections being converted to roundabouts. However, traffic management issues have also led to some roundabouts being treated via signalisation to improve traffic flows.

To enhance the understanding of the safety implications of signalisation as a treatment for roundabouts, this project utilised Empirical Bayes methodology to determine the change in safety for roundabouts treated in this manner. This methodology overcomes regression to the mean limitations and accounts for changes occurring over time that may otherwise impact the safety assessment of the treatments. The process utilised Safety Performance Functions calibrated to the local geographic region and intersection type to estimate the number of crashes that would have occurred at each intersection had the treatment not been applied. This is estimate was compared to the actual number of post-treatment crashes at each site to determine the safety effectiveness of treating roundabouts via signalisation of the roundabout and conversion to a signalised intersection.

The safety effectiveness of signalisation treatments is dependent on the type of crash being assessed; therefore, separate safety performance functions are required for various crash types to allow for accurate safety assessments. The safety effectiveness of a treatment is more closely related to the type of roundabout being treated than the treatment being applied. Results revealed that the signalisation treatment for four-legged roundabouts tends to decrease the total number of crashes at each site. Conversely, treatment of three-legged roundabouts increased in the number of crashes. The results indicate that signalised intersections can be considered safer than roundabouts in certain conditions on the Central Coast of NSW.

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Item Type: USQ Project
Item Status: Live Archive
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
Qualification: Bachelor of Engineering (Honours) (Civil)
Date Deposited: 03 Jan 2023 05:01
Last Modified: 26 Jun 2023 02:58
Uncontrolled Keywords: roundabout, crash, safety assessment, empirical bayes, New South Wales, signalisation
URI: https://sear.unisq.edu.au/id/eprint/51846

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