Gap setting control strategy for connected and automated vehicles in freeway lane-drop bottlenecks

Commercial automated vehicles equipped with adaptive cruise control (ACC) systems offer multiple gap settings that determine their longitudinal behaviour. This study introduces two novel strategies-inflow control and combined control-that leverage the distinct driving behaviours associated with different gap settings in connected and automated vehicles. These strategies aim to enhance traffic efficiency in freeway lane-drop bottlenecks, where capacity drops are common, by maintaining bottleneck occupancy at the target level using a proportional-integral-derivative controller. Simulation experiments were conducted using VISSIM to validate the proposed strategies. The results from a hypothetical lane-drop bottleneck indicate that the proposed strategies enhanced both efficiency and safety across all simulated demand levels, with the combined control outperforming inflow control by redistributing the relative positions of vehicles before the mandatory lane changes using a new gap setting. Moreover, the proposed strategies were effective under all the simulated market penetration rates (MPRs), where better performances were demonstrated at higher MPRs. An evaluation of a calibrated real-world network further demonstrated the potential of recommending gap settings to drivers of ACC-equipped vehicles using variable message signs to enhance freeway efficiency in the near future. Here, two strategies are proposed that control the gap setting of CAVs equipped with ACC systems, and the longitudinal behaviours of different gap settings were calibrated from the state-of-the-art commercial AVs' trajectory dataset. Simulation experiments were conducted in both hypothetical and real-world networks using VISSIM to validate the proposed strategies. The findings of this study demonstrate that controlling the gap settings has promise in improving the operational efficiency and safety of lane-drop bottlenecks on freeways. image