The choice of rubber tired or steel wheeled vehicles for a mass rapid transit (MRT) system or for a personal rapid transit (PRT) system involves a number of considerations. For the PRT system, the rubber tired vehicle possesses advantages in its ability to utilize steeper grades and shorter radius curves. The rubber tired vehicle can, if required, operate without a fixed guideway. It is more economical than the steel wheeled vehicle for PRT application. The steel on steel system seems to have little application to PRT as PRT is defined in this paper.For MRT systems, the advantages of the steel on steel system seem quite evident. Capacity, operating speed, and passenger comfort are increased with the steel on steel system. Energy requirements and the need for environmental control are decreased with the steel wheeled system. Capital costs for the infrastructure and the systemwide elements of the system decrease with the use of a steel wheeled MRT system, as do maintenance and operations costs.