Signalised Roundabout Studies - Brunei
The Nation of Brunei is a small sovereign state located on the north coast of the island of Borneo, with a liking of large roundabouts on their motorway, and arterial road interchanges. In a collaborative project with an Ex-pat local consultant, TDG has recently been involved in a project looking at two such roundabouts to extent their life before the perhaps inevitable grade separation is required.
These large roundabouts including the “Subok” Roundabout shown below, suffer from significant congestion at certain times of the day.
One of the first challenges was developing an understanding of the traffic demands. Traffic patterns are different to New Zealand with more distinct peak flow periods in the middle of the day and early afternoon associated with travel to and from prayers by the majority Muslim population.
For the Subok roundabout TDG developed both Linsig and Paramics models of an upgraded signalised layout, expected to add 10 years of life to the roundabout. The concept design is shown below.
The more congested Berakas Roundabout, shown below had more challenges with an unhelpful layout and very heavy right turn flows on some entry arms.
While this roundabout remains a work in progress, the latest concept shown below utilises the imbalanced location of the roundabout legs to its advantage by signalising an exit leg, with good upstream separation on the circulating carriageway to accommodate queuing, and provides a cut-through route for the heaviest right turn movement, removing this traffic from the circulating carriageway. It might not be the “Swindon Magic Roundabout” but it shows potential.
(Duncan Wilson, July 2016)
Tagged traffic engineering, modelling, transportation planning, traffic signals, sustainability.