Analysis of Traffic Flow through Roundabouts for Improving Performance

McLean, Aaron (2018) Analysis of Traffic Flow through Roundabouts for Improving Performance. [USQ Project]


Increasing population in a city usually creates traffic congestion, due to the lack of transport infrastructure facilities. To cope with traffic congestion at any intersection, upgrades take place, allowing for greater traffic volumes to pass through. The current consensus in Transport Engineering is that when upgrading intersections, the natural progression is to upgrade from Unsignalised, to Roundabouts, to Signalised Intersections as the traffic volume increases. This project aims to investigate and challenge this generalised thinking by seeing whether, in certain circumstances, roundabouts are better for improving performance along a corridor than signalised intersections. This project looks at analysing the corridor along Hume Street, from Perth Street to Long Street. This corridor was chosen as it suffers from congestion issues, and is seen as one of the main streets in Toowoomba. This corridor consists of three roundabouts in-between two major streets, James and Alderley Street.

Modelling software such as SIDRA and TRANSYT-7F were proposed to be used to model traffic flow through the corridor. They were chosen because they both analyse intersections in two different ways, SIDRA analyses each intersection individually, while TRANSYT-7F analyses the corridor as a whole. For the SIDRA analysis, the signalised intersection alternatives were one-lane intersections, like the roundabouts. This was to minimise the variables between the two intersection types. The TRANSYT7F model was set up to analyse three different operating scenarios, where the corridor is all roundabouts, all signalised, and one signalised. This was to see how much of an effect the signalised intersection has in the corridor.

Unfortunately, in the analysis, the TRANSYT-7F model wouldn’t work, no matter what was tested. The exact reason as to why it didn’t work was never found, however, a couple of error logs were determined to be part of the reason. The SIDRA analysis did work, however, and produced results that make sense in the scenario given. The roundabouts perform better than signalised intersections in terms of degree of saturation, queue lengths, and delay, while Long Street performs the worst of the three intersections. The queue lengths were found to increase along Hume Street with signalised intersections, while the delay along the side streets was found to also increase with signalised intersections installed.

In conclusion, the model tested to see which of roundabouts or signalised intersections are the best for the analysed corridors performance. Form the testing completed, it was found that the roundabouts perform the best along the corridor, however, Long Street has reached the maximum capacity of a roundabout, and would need to be upgraded to two-lanes to better improve performance.

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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: 05 Sep 2022 03:24
Last Modified: 29 Jun 2023 01:56
Uncontrolled Keywords: traffic flow; roundabouts; improving performance

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