Double crossover diamond interchanges (DCD: aka DDI – diverging diamond interchange) are popularand promising alternative interchanges that are increasingly being implemented nationwide. The mostunique feature of a DCD interchange is that through movements on the arterial road have to cross eachother twice to complete their movements, while enabling left turn movements from the arterial to thefreeway to proceed without stopping at the downstream intersection. Consequently, interchanges withheavy left turn movements are good candidates for DCD implementation. This unique feature of a DCDinterchange means that there is a need to research the lane utilization at the upstream approachintersection of DCD interchanges, as the lane use could be unbalanced. This unbalanced lane utilizationcould a significant effect on operations at the first crossover and the interchange as a whole.This study examined lane utilization factors provided in the Highway Capacity Manual 2010 forconventional diamond interchanges, and found that they are not generally applicable to DCDs. The studythen proposed a lane utilization model calibrated with field data obtained at three DCD sites. The newmodel fit observed conditions at the DCD sites better than previously developed HCM factors. The modelwas then validated using three additional DCD interchanges, and validation results confirmed that thenew model adequately predicts DCD lane utilization. The authors recommend that DCD designers andanalysts use the new model where it is applicable, but also that more research be conducted to find laneutilization factors for other DCD configurations.
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