I have found that such an optimum speed is lower than intuition generally suggests, and thus advise that speed not be simply picked but considered a parameter to be determine during a comprehensive study. Capacity I address this topic in a paper being considered by the ATRA Board, in which it is shown why PRT matches capacity to demand. If the demand is completely uniform, no empty vehicles are needed. In many applications, simulations have shown that generally about one-third of the vehicles will be empty. We take all of them into account in computing the total cost per passenger-mile.
Every transit system has a certain amount of deadheading.
A problem with scheduled systems is that to provide reasonable service in off-peak periods vehicles must be run with very few or no passengers. This substantially increases the daily average load factor of moving vehicles, and thus improves energy efficiency and reduces operating cost quite substantially. UMTA personnel realized this at least by the late 1970's. The volume requirement is modest because it is not necessary to remove a particular vehicle at any time. Land Use PRT uses land only for posts and stations, which typically take less than two percent of the land.