Unlocking potential capacity benefits of electric vehicles (EVs) with adaptive cruise control (ACC)

Today’s mainstream vehicles are partially automated via Adaptive Cruise Control (ACC) that relies on on-board sensors to automatically adjust speed to maintain a safe following distance. Contrary to expectations for automated vehicles, ACC may reduce capacity at bottlenecks because its delayed response and limited initial acceleration during queue discharge could increase the average headway. Fortunately, EV’s unique powertrain characteristics such as instantaneous torque and regenerative braking could allow ACC to adopt shorter headways and accelerate more swiftly to maintain shorter headways during queue discharge, therefore reverse the negative impact on capacity. This has been verified in a series of field experiments, which demonstrate that EVs with ACC could potentially achieve a capacity as high as 2,931 veh/hr/lane in steady-state conditions, and it can be sustained in non-steady-state conditions where speeds fluctuate and queues form.