Searching for the Optimum Dualmode System


Francis Reynolds

In response to Kirston Henderson (MegaRail)

Andreas Steingroever and Rasmus Krevet (Autoshuttle)


"Further Critique" by J. Richard Guadagno (InTranSys)


Let us for now define a dualmode transportation pallet as the assembly required to mate a street-mode vehicle to an automatic guideway. Note that nothing is said there about where a pallet is to be taken or stored when it is not serving its purpose. Most frequently the plan is that when a pallet is not in use it will be separated from the car and sent to another customer, or it will be stored on the guideway, at a station or in an off-line depot.

But the pallets could instead be designed to separate from the guideway system and remain attached to the cars. A permanently attached pallet integrated with the car is the feature that makes a true-dualmode vehicle. I greatly prefer this option because I will want to use my pallet at a moment's notice, and won't want to wait until a commercial one becomes available for rent from the guideway company. I will effortlessly store my pallet in my garage along with the motor and all of the other parts of my car. An optimized integral-pallet system offers greater efficiency and convenience than separable pallets. And in the long run it will cost me less than renting a pallet every time I need one.

The logic of the above arguments is of course strongly influenced by what the guideways will consist of and what the optimum pallet for that guideway will be. But conversely, its ability to accommodate cars with integral pallets should be a major factor in the selection of the guideway type.

If the guideways have steel rails and the pallets have big heavy flanged steel wheels, then I would not be interested in owning such a pallet as a part of my car. Driving on the streets with the steel wheels raised and the rubber-tired wheels lowered would not be appealing. If steel wheels are used in the guideway mode I definitely vote for separable pallets that stay with the guideway system. In this respect I support the Washington DC to Orlando Auto Train, and similar systems on present railroad lines. The obvious advantages of such low-tech dualmode systems are low cost, short implementation times, and a minimum of political and environmental snags since they accommodate existing automobiles on existing infrastructure. But the convenience, speed, capacity, and environmental advantages offered by such systems are quite limited; therefore they are interim solutions only. But they, unlike most interim transportation proposals, make sense.

If the dualmode vehicles are to be supported by their street-mode pneumatic tires on either guideways or modified highway lanes, then putting the pallets in the cars makes total sense. The "pallets" would then be little more than the added automatic guidance and control systems. But Automated Highway Systems with "Smart Cars" have many safety concerns, do nothing for the environment or the fuel shortage, and have other major disadvantages as we have seen from the National Automated Highway System Consortium (NAHSC) work. In my opinion the effort by PATH and CalStart to resurrect AHS is a loser, because there are much better dualmode concepts available than Automated Highway Systems would be.

If the guideways are maglev, integrating the pallets with the cars makes good sense in general. HiLoMag is a maglev system, and nothing that we have learned in the last four years has altered our conviction that maglev is by far the best choice for the automated mode of a dualmode system. Maglev trains will disappear because the basic concept of trains is obsolete, but maglev per se is a highly efficient and wonderfully useful technology when used in the right applications.

Originally HiLoMag was configured to levitate the cars above the guideways. It was obvious however that having the cars suspended below overhead maglev guideways would have some major advantages. These include: lower land requirements including multiple-use of land; probably lower cost guideways; easier use of highway median strips; gravity enhancement of car stability rather than its degradation; elimination of problems due to snow, ice, and guideway debris; and complete elimination of collisions with pedestrians, animals, and street or highway vehicles.

A major disadvantage of a suspended-car true-dualmode system could be the inherent ugliness of integral pallets extending above the cars in street-mode. And of more practical importance, the added height of the cars due to the pallets sticking up would prevent them from fitting into most garages, and there would be added aerodynamic drag in street mode. But who says the integral pallets have to be sticking up in the air when the cars are not suspended from the guideway? The possibility of somehow retracting overhead pallets onto or into the cars for street use was considered early in the HiLoMag work, but at that time no adequate retraction configuration was envisioned. The possibility of retracting overhead pallets was recently examined in more depth, and a very promising configuration was found. HiLoMag now has overhead guideways with suspended true-dualmode cars. Airplanes retract their landing gear, and HiLoMag cars will retract their pallet magnet assemblies.

The pallet-retraction linkage will be a pantograph, reminiscent of the pantograph trolleys above some electric trains, but lower than the pantographs on trains. Train pantographs appear as parallelograms when in use; but on HiLoMag a pantograph at each end will be completely retracted into a fairing on the roof of the car when it is in street mode or in the garage, and the pantographs will be nearly extended when supporting the car.

"Nearly extended," but not completely, because the pantographs will have light springs holding the opposing central link joints somewhat apart. The resulting soft suspension will permit a smooth ride with a higher degree of guideway waviness (less-costly guideways) than would be acceptable with a rigid suspension.

Unlike airplane landing gears, which tend to redeploy by the force of gravity in the air and tend to retract from the weight of the airplane on the ground, gravity will be aiding the desired operation of pallet pantographs in both the extended and retracted modes. And the weight of the car will load the pantographs in tension, so for equivalent vehicle weights the pantographs will be far lighter than airplane landing gear struts (which must withstand long-column and bending loads).

We envision the specification of a maximum width and a maximum height for dualmode vehicles, and a maximum weight per unit of length. Therefore vehicles such as buses and freight containers won't be built with excessively large cross sections, but can be built longer in order to carry heavier loads. On long guideway vehicles the integral maglev pallets would also be built longer in order to support the greater load. A magnet assembly will be located near each end of both regular and long vehicles. The pallet supports on long vehicles may use a built-in swiveling feature reminiscent of the swiveling wheeled trucks used on railway cars, to keep each of the widely separated long magnet assemblies tangent to the guideway in turns. And note that most of the long guideway vehicles will be for single-mode applications, so their integral pallets need not be equipped with retractable pantographs.

The street-mode electric motors can be built into the wheels, so no through axles will be required, the passengers will sit lower, and the total car height including retracted roof pallets may be no greater than that of existing automobiles. Off-road vehicles can keep the ground clearance they need, because these fuel guzzlers (if there is any fuel left to guzzle by then) won't be candidates for guideway travel.

Remember that HiLoMag is proposed as a multi-use system that will accommodate most private and commercial cars and light trucks, dualmode transit buses, dualmode rental cars, dualmode taxis, and single-mode (guideway only) driverless cross-country busses, and driverless freight vehicle "magtainers." HiLoMag would build one nationwide guideway grid that could carry nearly every type of vehicle carried by the Interstate Highway System plus a few types of its own. And it would completely solve or greatly reduce practically all of our existing transportation and transportation-related environmental and energy problems. End of spiel.


First, addressing Kirston Henderson (MegaRail).

Henderson devotes several paragraphs to recognizing the many disadvantages of using separable pallets or "ferry vehicles" as they are called in his system. He promises pallets with reduced drag, reduced cost, etc., to keep the pallet problems "to an acceptable minimum." We gleefully point out that zero separate-pallet problems by their complete elimination would be still more "acceptable." If a particular dualmode system can't use true-dualmode cars at the outset, the system-configuration choices should be reexamined.

Remember that automobiles now in use will be worn out before MegaRail or any other major system could be built. Therefore people should not be asked to rent ferry vehicles or other separate pallets at a higher long-term cost than the price differential between ordinary cars and true-dualmode cars. Most of us choose to buy cars rather than rent them, and logically that "buy" decision should apply to all parts of the car that are needed, including pallets on future cars. We do not have to build a system to conform to the automobiles that Detroit and the other builders now choose to build. Their (our) cars will change, because they will have to change for several reasons. We are in the forefront of defining the nature of some of those changes.

And even if our present cars would still be operable then, most of us wouldn't be able to drive them because the little bit of gasoline left by then will be prohibitively expensive. The media implies that high gasoline prices are due to corporate greed, the Arabs, or politics; but the root reason for high and climbing fuel prices is simply supply-and-demand. The demand for petroleum is enormous and growing rapidly, and the supply is all but gone—forever. "Dualmode: We need you now." But I digress.

Integral pallets will rapidly become standard equipment on all cars, the same as closed bodies, electric lights, and electric starters previously became standard equipment. The standard-integral-pallet change can occur at the same time as the elimination of gasoline and diesel engines. Insistence upon keeping our new cars as much as possible like our present automobiles would seriously degrade their utility and increase the cost of the new system. The driving public will have to get used to cars that look and perform differently than those they are used to. That is true whether there is ever a dualmode system of not. The fuel crisis makes a major transportation revolution inevitable. The question is whether mankind will collectively have enough sense to build a system that would minimize the negative aspects of that revolution.

I certainly hope that the money to build MegaRail or any other dualmode system does not come from government taxes or debt. Dr. Hopkins assured us that it could never be government money anyway. The government is much too set in its ways. The more we can keep big government out of it the better. A good dualmode system can pay for itself and make a profit because it will provide services most travelers and businesses need and want. Therefore it should interest investors and big corporations.

The HiLoMag team strongly opposes the use of rubber tires in the guideway mode. It is true that they provide quiet smooth operation, but that is about their only advantage. They would be a continuing replacement expense, they waste significant energy through flexure, and they would have poor reliability and safety.

Henderson seems to reject maglev for MegaRail largely on the basis of cost. Even in the event that MegaRail is proven to cost less than a maglev system, we feel that choosing rubber tires would be a case of "penny-wise and pound-foolish." Maglev will have great advantages in a dualmode system beyond the obvious zero-wear feature. For one thing, with some forms of maglev linear-motor propulsion can be built integral with the levitation system essentially for free. Two major requirements met for the price of one. And the use of linear synchronous motors will eliminate most of the complex, costly and unreliable electronic guidance-and-control systems otherwise required.

Addressing Steingroever and Krevet (Autoshuttle):

We don't see that the Autoshuttle people have "proved" that Reynolds' previous contribution made any erroneous assumptions. Sometimes "proofs" are based upon false, debatable, or unnecessarily restrictive assumptions. We decline to make any "direct comments on [their] detailed calculations," since we don't question their mathematics. However, we do question some of the configurations and conclusions they chose to "prove" by calculations.

On a more positive and friendly note, we have much admiration for the Autoshuttle group. Their website  is excellent and comprehensive, and the English translation is very good. Unfortunately even the best of translations usually don't give quite the clarity of communication provided by an article written in the language of the reader. But thanks for the very welcome translation. Regrettably we can't offer you German or other translations of most English-language transportation articles.

We fully agree with most of the choices in the Autoshuttle system proposal. In our opinion, its use of dualmode, magnetic levitation, linear-synchronous-motor propulsion, the speed selected, offline acceleration and deceleration, full-speed switching, and the use of convoys are all the right choices. We disagree with Autoshuttle's use of large separable closed pallets or "cabin cars". And if Autoshuttle can really have a system ready for use in nine years (as stated at their website), things must happen much faster in Germany than they do in the United States.

Their closed cabins look very nice, and in convoys they would be aerodynamically "clean," but they are big. These pallet cabins would be expensive, heavy, unnecessary, and they would cause the empty-pallet problems we have discussed, but I will limit this discussion to the aerodynamic drag considerations. We agree with Steingroever and Krevet that the drag of individual automobiles is high on highways and autobahns, the drag of separated conventional cars on open pallets would be worse, and we agree that the formation of convoys with closely-spaced cars would be a big help. But it appears from the website illustrations that the frontal area of the Autoshuttle automobile cabin would have roughly three times the frontal area of the automobile itself; and other factors being equal, aerodynamic drag is theoretically proportional to frontal area.

We know that present automobiles were designed for styling appeal, interior space, and with some attention to independent-car drag. They were never intended for convoys, and the shape of sedans, for instance, would limit convoy drag reductions. Even with the much smaller frontal area of exposed automobiles Autoshuttle claims that a tight convoy of exposed cars would have higher drag than that of the same group of cars in an Autoshuttle cabin convoy. This conclusion, which we don't challenge, seems to have led to Autoshuttle's decision to use closed cabin pallets.

But our present automobiles will be all but gone by the time Autoshuttle could be built. Therefore we should be designing a high-tech transportation system based on twenty-first-century cars, not upon troubled twentieth-century cars. As discussed previously, the public will have to accept different cars than we now have. Along with different propulsion systems these new cars can have true-dualmode additions (integral pallets). Further, they can be shaped externally for minimum drag when running in tight convoys on the guideways without separable pallets.

The shape of existing sedans would be a poor choice, but present vans and minivans are already fairly close to the ideal shape for convoying. A few changes, mostly in the front and back, and fairing underneath and around the wheels, and we would have a vehicle with a convoy drag coefficient almost as good as that of the Autoshuttle cabins. The difference surely wouldn't be as great as the three-to-one difference in frontal areas. So we argue that exposed-car convoys can have less total drag than cabin convoys. We suggest you rethink your decision to use cabins.

Your rebuttal stated that "Only about 15% of the traffic volume is of the type 'high-capacity corridor'." (From the German Ministry of Transportation). Fifteen percent may also be about right for the United States, depending upon the specific definition of "high-capacity corridor." But Autoshuttle appears to be restricting its market to high-capacity corridors, while HiLoMag guideway travel is being proposed for almost all car trips of more than about five kilometers. Where you predict that less than 15% of total car mileage would be on Autoshuttle, we predict that 60 or 70% of the total would be on the HiLoMag guideways.

When the extensive guideway grid is fully developed, that mode may replace as much as 95% of existing highway travel. The percentage of the total travel that will remain on the streets in manually driven mode will eventually be 30 to 40% or less, depending upon the specific area under discussion and the time of day. This estimate takes into account the fact that there will be automatic parking directly from the HiLoMag guideways in dense areas. So a high percentage of cars will never leave the guideways and enter the street mode at all in the cities and at other major destinations. Thus, with direct automatic parking, HiLoMag would greatly reduce central-area street traffic as well as pick up the lion's share of existing highway traffic.

Since we predict that street-mode travel will be secondary, and we know that street speeds will be low, we are not concerned about the somewhat higher individual-car drag coefficient resulting from optimization of the cars for convoying. Cars will be designed for minimum drag in the mode where that design will save the most energy, the guideway mode. And speaking of energy, we will spend less of it carrying integral pallets around in slow street-mode for short distances than we would in shuttling empty pallets around on the guideways as great speed and for long distances.

Addressing Richard Guadagno (InTranSys)

Dr. Guadagno didn't talk about HiLoMag in his last contribution, but I am going to say a few words about his work anyway. In our opinion his "Integrated Transportation System" has a great many features to admire. The choice of an elevated enclosed guideway with the cars suspended below would keep the tracks clean and prevents collisions with vehicles and objects on the ground. The LSM propulsion proposed would synchronize the cars and eliminate a lot of expensive and unreliable proximity-sensing and velocity-control equipment. And Guadagno's website has an excellent but frightening discussion of the imminent worldwide energy crises and their likely effects upon transportation.

As with both Autoshuttle and MegaRail, we take issue with the use of separable pallets ("carriers" on InTranSys) from the standpoints of aerodynamic drag, cost, weight, empty-pallet routing and storage requirements, and pallet-caused user delays. The disadvantages of separable pallets far outweigh their advantages. The HiLoMag retracting-integral-pallet concept is free for the taking. All HiLoMag ideas are in the public domain, and people are encouraged to "steal" them.

We would like the steel wheels of the InTranSys carriers better than rubber tires on the guideways. But we don't like guideway wheels of any kind nearly as well as we like maglev guideways. Since Guadagno has chosen to use high-tech LSMs, his choice of low-tech steel wheels over maglev is surprising. We note that a number of people around the world think that maglev would make better railroads than steel wheels on rails do. They are right, but the point they are missing is that single-mode railroads of all kinds are obsolete. Maglev is superior on most counts in the right applications.

I fully concur with Dr. Guadagno's last paragraphs where he expresses great frustrations over the waste of government transportation money, continued support of the archaic internal-combustion engine, and other difficult-to-change dumbness. How do we get the right people to listen? And who are the right people? The U.S. Department of Transportation and the automobile industry should be the main organizations to tackle, but as we repeatedly see, that is going to be a tremendous job.

If we innovative-transportation dreamers can come to some better agreement among ourselves on what the optimum system should be, then perhaps we can take a more unified stand against the forces of stalemate and early-twentieth-century thinking. I strongly feel that we need to push for a single standardized system all over the United States, and if possible in other countries. The lack of standardization on railroad track gage over a century ago was a major problem, but lack of standardization on dualmode in the future would present still greater problems.


Last modified: August 13, 2002