The problem of precise longitudinal control of vehicles to follow predetermined time-varying speeds and positions has been solved. To control vehicles to the required close headway of at least 0.5 sec, the control philosophy is different from but no less rigorous than that of railroad practice. A PRT system can be designed with as good a safety
record as any existing transit system and, because of the ease of adequate passenger protection, quite likely much better. The basis for the control of a fleet of PRT vehicles of arbitrary size is a complete set of maneuver equations. The author's conclusion is that the preferred control strategy is one that could be called an "asynchronous point
follower." Such a strategy requires no clock synchronization, is flexible in the face of all unusual conditions, permits the maximum possible throughput, requires a minimum of maneuvering and uses a minimum of software. Since each vehicle is controlled independently, there is no string instability. Since the wayside zone controllers have in their memory the same maneuver equations as the on-board computers, accurate safety monitoring is practical. To obtain sufficiently high reliability, careful failure modes and effects analysis must be a key part of the design process, and the control computers must be checked redundant.