Capacity of automated highway systems: merging efficiency

Lane-changing and merging cause disturbance to AHS traffic flow and hence reduce the capacity of an AHS lane from the theoretical maximum capacity to an actual capacity. This paper concentrates on the more complicated maneuver-merging. The actual capacity depends on the vehicle-following rule and the merging discipline. We study three basic vehicle-following concepts: autonomous individual vehicle, cooperative individual vehicle and cooperative platooning. For each of these three, multiple merging disciplines are developed and studied. For all three vehicle-following concepts, merging disciplines have been developed that lead to 25% or less reduction from the theoretical maximum. Without some form of coordination, e.g., yielding, for the autonomous individual vehicle concept, capacity reduction due to merging could be drastic, e.g., 50%+. If the cooperative platooning concept is implemented in such a way that only one vehicle can be released into the mainline stream when a sufficiently large gap approaches the merge point, then a reduction of 70%+ from the theoretical maximum capacity has been observed.