In 2014, Shaun undertook a study tour to investigate the concept of diverging diamond interchanges (DDI). These revolutionary new interchanges are growing rapidly in number across the United States for their ability to efficiently manage competing traffic flows with reduced delay and infrastructure cost. The design takes the opposing traffic, through and left turning movements (right turn movements in Australia), and manoeuvres them onto the opposite carriageway through the intersection. Thereby allowing the turning traffic to make their turn unopposed.
This tour involved viewing sites in Reno Nevada, Springfield Missouri and Lexington Kentucky. Six interchanges were studied across the US and this incorporated meetings and workshops with the various County and State transport representatives. The tour also investigated two DDI’s in Paris, including the location of the first DDI in the world. The study tour concluded that these innovative solutions are indeed worth investing in for Australian traffic conditions with potential for significant benefits to be achieved in reducing intersection delay, accident rates and infrastructure costs. However, as these interchanges require drivers to undertake unfamiliar manoeuvrers through the interchange, care should be taken with respect to safe design and education/communication with the travelling public. Also, these solutions are not appropriate for all interchanges especially those that incorporate bus lanes and extremely high right turning movements that require a significant number of lanes. We understand that VicRoads has earmarked the first site to undertake a pilot of this solution and we look forward to seeing it’s progress.