About

Taking inspiration from a range of alternative junction designs commonly used in the United States, there have only been a few tentative steps of introducing ‘alternative design’ junctions to resolve congestion problems at T junctions in the UK. Among these, two ‘Displaced Right Turn’ (DRT) T-junctions have been built. Alternatively called a ‘Continuous Flow Intersection’ (CFI), they work on the principle of ‘swapping over’ the opposing streams of traffic on the minor road arm to enable unopposed right turns to be made at the main junction. This enables a simplification of the traffic signals staging, delivering improvements in capacity and reducing delays. In undertaking this study, a range of hypothetical XT junction layouts varying in size and configuration have been developed and modelled. The results of the modelling exercise suggest that depending on the layout tested, traffic volume and the degree of active travel facilities provided, the adoption of an XT junction is likely to result in an additional spare capacity up to 33% in comparison to a standard T junction.

 

This spare capacity could either be used to benefit traffic capacity, congestion, and delays or to improve crossing time and clearance allowance for active travel modes – all without a detrimental effect on traffic and potentially at a lower cost, without resorting to more expensive infrastructure. In addition, the results show up to 100% traffic signal cycle time savings based on the level of active travel provision. Furthermore, the most significant environmental benefit is the scope to reduce the operational carbon dioxide CO2 emissions, potentially by up to 35%.

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