Palleted Automated Transportation (PAT)

vehicle on
pallet in enclosed guideway This is a transportation system giving dual-mode capabilities through the use of flat cars or pallets that take people in small buses or personal vehicles and that are routed automatically on guideways. These guideways have off-line stations (in common with most PRT systems) giving the possibility of non-stop travel from many origins to many destinations. Three illustrations of stations are available. One is an artist's sketch . A second shows the layout of a typical PAT rapid transit station. A third shows a station that provides for both freight and auto loading. Such systems can give very high capacities for lightweight vehicles on small guideways so long as the headway or spacing between vehicles can be safely kept small.

A pallet or flat-car system was chosen over one involving dual-mode vehicles (i.e. vehicles able to travel on the guideway and on public roads) because of safety and cost concerns. The safety problem is obvious: vehicles used on public roads would need rigorous inspection each time they join the guideway. The would also need to carry guidance, control and propulsion equipment for both forms of travel, making them heavier, more dangerous in accidents and less fuel-efficient in their use on the roads. It was decided that vehicles completely captive in the system but capable of carrying a wide variety of road vehicles and freight would combine maximum safety with the lowest practicable cost and fuel use.

The propulsion and control system chosen by MIT ( and patented on Independence Day 1972, # 3.673,966, long since expired) was to drive the pallets by synchronous vertical-axis electric motors driving pinion gears engaging a rack on a low left-side guiding wall. Illustrations of a geared-screw synchronous accelerator and a synchronous rack/pinion propulsion and control system are provided. Not only does this system guarantee that spacing is accurately held, but it converts motors on vehicles going downhill into alternators, thus pumping energy back into the system. The critical entrances and exits from the guideway are made by the pallet engaging a right-hand guiding wall, on which the power is supplied at an appropriately varying frequency. A low-tech alternative acceleration/deceleration system was a variable-pitch screw drive by a trackside synchronous motor.

The PAT system was modeled on computers and on several small-scale working systems. Studies of the predicted use were made by substituting the PAT system for the Boston-area transit system (the MBTA). The results showed large gains in ridership and reductions in automobile and truck use. PAT was designed to be used in dense urban areas, where the guideway speed would be about 10 m/s, 22 mph; to extend to the suburbs at 20 m/s, 45 mph; and to be used between cities at guideway speeds of 40 m/s, 90 mph, perhaps located along the median of interstate highways. The automated loading and unloading of pallets would lead to outstanding levels of service for the movement of both people and freight. An illustration of what an auto and a bus on a pallet might look like is provided as is an aerial view of how a PAT guideway could be integrated with a typical freeway interchange.

The PAT group of students and faculty at MIT produced many reports on PAT and alternative systems. Many of the illustrations included here are borrowed from these studies.

The above was written by Professor David Gordon Wilson of the Massachusetts Institute of Technology in Cambridge, Massachusetts. He also provided the illustrations. More details can be obtained via e-mail from him.


Last Modified: September 1, 1997