Automated Transport: Where to Start?, Where to End?

PRT, "True" Dualmode, Palletized Dualmode, Maglev or What?

Can We Get Together On Standards and Present a United Front?


Van Metre Lund (

It is inevitable that a nationwide network of automated transport systems will be built in the future and that it will be used very extensively for carrying people and things, including autos. It is also inevitable that the auto in one form or another will co-exist with such systems and be used to get to and from stations of a such systems or to be carried by such systems either on a pallet or as a dualmode electric car using its electric motor as a drive source.

In the meantime and for many years to come, autos with internal combustion engines will continue to be used to deplete irreplaceable oil resources and pollute the atmosphere while tying up traffic and causing avoidable deaths, injuries and property damage. As I have argued in previous submissions to the Dualmode Debate page, carrying autos on pallets is one way of dealing with this very serious immediate problem. I have given as an example a 10-mile Autran system which has considerable hope of being constructed in the near future since it might operate profitably and require no taxpayer support. In one year, one such 10-mile system could carry autos through a distance of over 121 million miles, save 4 to 5 million gallons of gasoline, avoid 605 crashes with 10 fatalities and avoid monetary costs of over $10 million.

An advantage of any such Autran system is that once built, even if only initially for carrying pallets, it could be used in carrying passenger cabins, including cabins for PRT use, and freight containers, eventually to form part of a nationwide network. Autran systems could also be used for proposed "true" dualmode cars, albeit with some reservations. I have serious questions as to the desirability of maglev support of cars and as to the desirability of using the tires of cars to support and drive them on guideways. I will expand upon these issues.

The Autran System Is Compatible With PRT

The Autran system has a modular construction in that separate modules are formed by (a) load supports, (b) carrier vehicles, (c) guideways and (d) a series of electronic modules along the guideways. Each load support may be either an auto platform or pallet, a passenger cabin or a freight container and includes standard connections to upstanding posts of a carrier vehicle for physical support, for supply of electrical power and for data communications. Each carrier vehicle includes lower and upper wheels engaged with lower and upper tracks, the upper tracks being used to limit tilting of the vehicle, to apply increased traction when necessary and to control steering along the guideway and through converging and diverging Y junctions. In addition, each carrier vehicles includes electronic controls that exchange data with loads that are carried and that co-act with the electronic control modules along the guideways.

A certain degree of compatibility between a PRT system and an existing Autran system can be obtained simply by providing the Autran standard connections between a PRT cabin and a carrier vehicle that supports the cabin. At interfaces between PRT and Autran guideways, PRT cabins could then be readily transferred between PRT carrier vehicles and Autran carrier vehicles. Except for the standard connections, the carrier vehicles and the guideways of the PRT and Autran systems could have different constructions.

However, a higher degree of compatibility could be obtained by using PRT vehicles and PRT guideways with upper and lower wheels and upper and lower tracks at the same relative positions as used in the Autran system and by using compatible electronic controls and modules in and along the PRT vehicles and guideways. It would then be possible to move any PRT vehicle and associated cabin between any station along a PRT guideway to any station of the Autran system.

Reverse compatibility is not necessary and in many cases would be undesirable, particularly with respect to load capacity. For example, if an Autran system exists that can carry vehicles for longer distances between cities, and PRT systems are to be constructed in densely populated regions of the cities, it would be advantageous to use low load-capacity vehicles and guideways in the PRT systems and preclude movement of high-capacity Autran vehicles on the PRT guideways while still obtaining a one-way compatibility that permits movement of the PRT vehicles on the high-capacity Autran guideways. Since load capacity is not increased, the PRT guideway costs involved in providing such one-way compatibility should not be much higher than they would otherwise be.

Achieving such compatibility would have obvious advantages to Autran as well as to a PRT manufacturer. To the extent that Autran may have proprietary rights, I am quite willing to grant a license at reasonable terms to any PRT manufacturer that may be interested, perhaps under an arrangement that Autran may obtain a license under any rights held by the PRT manufacturer. I strongly believe that compatibility, cooperation and open standards will be very important for early adoption of automated transportation. In this connection, please consider my response of last May to comments by John Hopkins.

The Autran System Is Compatible With "True" Dualmode, but "True" Dualmode Has Problems

In HiLoMag, one type of "true" dualmode car is supported using cooperating maglev components in the car and along the guideway for support and movement of the car. The maglev components of the guideway and guidance components could obviously be supported on an existing Autran guideway. Another type of "true" dualmode car would be supported and moved on and along a guideway by the same tires used to support and move the car on a conventional street. This type of car could obviously be supported and moved on and along an existing Autran guideway. In each case, compatible electronic controls and modules could be used. Modifications may be necessary to obtain electrical power for the car during movement along the guideway, but there should be no insurmountable problem in using either type of "true" dualmode car on an existing Autran guideway. However, "true" dualmode has potential problems, particularly with regard to costs.

An important consideration in analyzing costs is that each dualmode car may move on a guideway only a few thousand miles per year, probably not more than 5,000 miles and more likely much less. By comparison, each pallet and associated vehicle of an Autran system may move cars through a great many miles each year, probably 150,000 or more, a ratio which is probably at least thirty to one and could be much more. In the 10-mile Autran system, the cost of one pallet and associated carrier vehicle is estimated at $15,000 and a pro-rata share of loading facility and guideways costs is estimated at $18,400 for a total cost of $33,400. This cost may be compared with the cost of equipping at least thirty and perhaps many more electric vehicles with the electronics, power pick-up, maglev and other features necessary for operation on a guideway as a maglev car or as a tire-supported car and adding to that a pro-rata share of guideway, loading facility and other costs that may be involved. Operating costs are also a consideration, especially as when considering tire-supported cars.

This analysis has not taken into consideration the "chicken and egg" problem in trying to get to a point where there might be a sufficient number of "true" dualmode vehicles for satisfactory operation from a financial standpoint. However, if in spite of this problem, "true" dualmode systems are to be advocated as providing the best long term solution, considerable attention should be directed to providing evidence that they can be justified on the basis of costs.

Costs and Other Problems With Maglev Support of Dualmode Cars: A Comparison With An Autran System Using Maglev

As to HiLoMag, Figure 3 shows a car that has tires and that must have an electric motor, batteries and all the other components necessary for an electric car that can safely travel on a street. The HiLoMag car also carries maglev components in the form of levitation and propulsion magnets which co-act with guideway maglev components that include guideway coils and guide rails. Expensive electronic controls would be required in the car and for energizing the guideway coils, especially during acceleration and deceleration of the car. The maglev components must support the full weight of the electric car or of a pallet that carries a conventional car, would probably need to be capable of levitating at least 5500 lbs., possibly more, and would need to be provided in all guideways of the system, including guideways that need operate only at lower speeds. I believe that the required electronic controls and the required maglev components would result in costs that are prohibitively high in comparison to those required in an Autran system.

Autran uses carrier vehicles supported by means of steel wheels to move between lower and upper steel tracks within a guideway. The cost of this type of support must surely be much less than the costs involved in using maglev for support. The wheels are driven through an electronically controlled multi-speed transmission from a standard 3-phase induction motor. This drive arrangement is highly efficient, the electronic components operate at much lower power levels and its costs must surely be much less than those associated with use of LIMs or LSMs. It is practical, safe, not expensive and highly efficient and can be safely used at speeds up to 100 MPH or more. It is submitted to be ideal for carrying people in passenger cabins or in their cars, especially when they are making their most frequent journeys which are through shorter distances. It is also ideal for carrying freight which need not normally be carried at high speeds and which, when energy consumption is considered, should probably not be moved at speeds greater than 85 MPH.

It is expected that the Autran system may include special high speed guideways used for the sole purpose of carrying people in aerodynamically efficient high speed cabins. The possibility of using wheeled carrier vehicles at high speeds has not been ruled out and might, in fact, be better than maglev when safety and costs are considered. However, I would certainly consider using maglev. In this connection, a fully loaded eight passenger high speed Autran cabin might weigh perhaps 2500 lbs., less than half of the HiLoMag load requirement and the costs of Autran maglev components should be proportionately less. More importantly, these components would be required only for the high speed maglev guideways and maglev cabins of the Autran system. No maglev components are needed for the lower speed portions of the Autran system.

The Autran system with separate high speed guideways will produce delays that would not be encountered with a system in which all cars and all guideways are equipped for maglev operation. However, any such delays can be of very short duration and should not present any serious problem. Most users will not frequently make long distance trips. When they do, it can be expected that they will be able to quickly board an awaiting maglev passenger cabin at an Autran maglev station, after walking, bicycling or driving to a the station or after a transfer at the station from a passenger cabin carried by a standard Autran carrier vehicle. It is also possible that high speed cabins may be carried at lower speeds by standard Autran carrier vehicles and to maglev stations at which the high speed cabins with their occupants are transferred to maglev carriers. In either case, any boarding delays can be minimal and, after boarding, the users may move at high speeds to distant stations from which they may rent cars or use any one of a number of possible modes of transportation to get to their final destinations.

In summary, HiLoMag would appear to involve much higher costs than an Autran system, with few if any advantages in performance.

Costs & Other Problems With Moving Dualmode Cars On Tires

Moving cars on tires presents the possibility of blowouts and of accidents in adverse weather conditions. Another safety problem is presented by the fact that owners of "true" dualmode cars may neglect to see that they are maintained for safe operation. In addition, tires result in traction losses that are much higher than those involved in using steel wheels and steel tracks. I believe that when capital costs are amortized and operating expenses are considered, the actual costs involved in equipping cars for operation on tires along a guideway and making the necessary additions to the guideway are substantially higher than those involved in the Autran system in carrying cars on pallets. This is especially the case when the large number of miles cars are carried per year by a pallet of an Autran system is compared with the average number of miles traveled per year by a dualmode car, as discussed previously.

In summary, moving cars on tires would involve greater safety risks, increased energy consumption and probably higher actual costs than in carrying ordinary cars on pallets by an Autran system.

Standards, Compatibility and Cooperation Can Promote Rapid Progress

As is indicated in foregoing discussions, appropriate standards could be of considerable benefit in creating compatibility among systems and in leading to progress in the building of a nationwide network that can carry passengers in PRT and other cabins, that can carry autos on pallets in a dualmode operation, and that can carry freight containers. The palletized dualmode operation is particularly important in dealing with the immediate and very serious problems that result from use of the automobile, as well as being a viable way to lead to development of the desired wide-scale network. Standards could also be very important obtaining the participation and cooperation of vendors of the various components required for building and operating automated transportation systems. Attention is again invited to the discussion in my response last May to comments of John Hopkins.


Last modified: October 16, 2000