Spacing and capacity evaluations for different AHS concepts

The inter-vehicle separation during vehicle following is one of the most critical parameters of the automated highway system (AHS), as it affects both safety and highway capacity. The trade-off between capacity and safety gives rise to a variety of different AHS concepts and architectures. In this study we consider a family of AHS operational concepts. For each concept we calculate the minimum inter-vehicle spacing that could be used for collision-free vehicle following, under different road conditions. For architectures involving platoons we also use the alternative constraint of bounded energy collisions to calculate the minimum spacing that can be applied if we allowed collisions at a limited relative velocity in case of emergency stopping. The minimum spacing is used to calculate the maximum possible capacity that could be achieved for each operational concept