Reaction to "Dualmode System Design Odds and Ends"


Kim Goltermann

It is my hope that Francis Reynolds and his team can appreciate that I apparently have singled out their HiLoMag concept for particular criticism, but the reasoning behind is that constructive criticism requires a more or less common understanding of things. HiLoMag is simply the concept I agree most with and although not without flaws I believe it has got the basics about right. There are, of course, a few things I disagree with and I have every intention to be open-mouthed about it. Maybe my critique can somehow contribute to make a good concept a little better.

Pneumatic tires

Despite it’s serious implications the Firestone scandal is not an argument against pneumatic tires. The managers of Firestone have demonstrated disastrous poor judgment and buyers will know how to punish them, as there are at least a dozen other more responsible manufacturers to choose from, producing proven and safe tires. Flawed and outright dangerous products reach the market all the time; sometimes it goes unnoticed for years and on a rare occasion or two the management of an involved company fails to react when they become aware of the blunder. It has happened before with all sorts of electric appliances, toys for children, airbags in cars, the cars themselves and even jet-engined aircraft. The Firestone affair is just the latest example, but will certainly not be the last. A future scandal could even involve MagLev dualmode cars if they were ever to become common.

Our coming dualmode transportation system could use pneumatic tires broadly similar to present tires, but nevertheless with important differences. Their condition will be continuously and automatically monitored so vehicles can be denied entry or be immediately shunted off at the nearest guideway exit if critical values for temperature, flexure, pressure or wear are exceeded. Eventually tires will probably also evolve, so they are optimised more for guideways than for streets, possibly leading to more sturdy and robust tires, which in turn will lead to a further drop in tire failures on the guideways.

While there are engineering means to avoid maybe 99% of the tire failures we experience today, at least in the controlled environment on the guideways, there will still be the very rare occurrence when a tire suddenly and unexpectedly blows. Will this have catastrophic consequences? Not necessarily. In a system where pneumatic tires are used merely to support the weight of a vehicle, while propulsion as well as guidance is by the means of magnetic forces (LSM), the consequences of a blown tire will be limited.

The magnetic forces will stay the vehicle on course and maintain its velocity. The rolling drag of a vehicle will increase if a tire is blown but the LSM will be powerful enough to overcome this and keep the vehicle in step with other vehicles. The weight on the blown tire will in part be shifted to the remaining tires, and although it will be a rough and uncomfortable ride to the nearest guideway exit no collisions will occur. This ability to compensate for a blown tire and continue normal operation is unique to a LSM powered system, while systems utilizing vehicle mounted electric rotary motors will be in trouble should a tire ever fail.

Switching principle

Although I understand the concept of the binary guide-left, guide-right switching and guidance principle favoured by HiLoMag, InTransSys, Taxi2000 and others, switching still worries me, Francis. It is precisely the concept of a vehicle mounted and controlled switch in conjunction with a high-speed, short-headway and high capacity dualmode system that I cannot agree with. The Morgantown system you refer to can hardly be considered high-speed, short-headway or high capacity compared to the dualmode systems being envisioned on these debate pages. When I call for a switching principle "that can accomplish the switch function in a fraction of a second" I’m not thinking of vehicle mounted mechanical devices, but of a guideway mounted preferably non-mechanical switch.

You write that if the switch "fails to move when it is ordered to, or if no order is received, that vehicle may be misdirected, but no accident will occur." Well, I will have to disagree with that assumption. If we consider any kind of guideway junction (the drawing of a junction provided on the HiLoMag pages is a good example) where guideways split into two, just to merge with other guideways shortly afterwards, we will understand that even one misdirected vehicle is one too many and could easily have disastrous results. A misdirected vehicle could suddenly be heading for a merge where another vehicle is "scheduled" to arrive at the very same split second. If the traffic flows on the guideways are dense (as we all hope they will be) the probability that two vehicles will enter a merge simultaneous will be high if a misdirection ever occur, and that situation is little short of disastrous.

With millions of vehicles, all maintained by individuals to varying standards, misdirections are sure to be a relatively common occurrence considering that not only can the mechanical switch fail but the on-board control computer can as well, and the communication between way-side routing control computers and a vehicle could be interrupted, distorted or even manipulated. All these things summed up have convinced me it will be necessary to adopt a switching principle allowing no misdirections even if several systems or parts onboard a vehicle fails. A system operating with high vehicle densities will have to be in absolute control of all vehicles at all times, and this can in my opinion only be accomplished with a guideway based switch controlled by multiple routing control computers.

The need for a guideway based switch could possibly torpedo a dualmode concept or two, but so be it. If nothing else at least the proponents of these troubled concepts will have to come forward and make the case why they think I have gotten it all wrong.

Guideway freight vs. fewer air-travelers

It is surprising to learn that HiLoMag will not accommodate routine non-perishable freight on its guideways and that we therefore shall continue to rely on diesel powered eighteen wheelers for most of our freight. We have to get our priorities right and remember that we are planning for a day when fossil fuels will be either non-existent or at least very expensive.

While fast passenger transit, whether by aircraft or MagLev dualmode cars, is not essential to our society or more specifically; to our economy, cheap and timely transport of all sorts of freight is. Without cheap transport of freight our present high standards of living can neither be sustained nor improved. Furthermore, routine non-perishable freight will be a prime source of income for future guideway operators. Can we really afford to ignore the needs of the immense freight market when we design our dualmode system? Of course not!

I have said it before, but will repeat it here: Short haul air travel is destined to become land-based anyway, when fossil fuels becomes a scarce and expensive commodity, so there are no reasons why we should let the needs of air-travelers be a prominent design rationale for our coming dualmode system, especially not if we thereby compromise more urgent objectives.

Magnetic Levitation

Not much news to add on this subject, as I’m not opposed to MagLev per se. Although I agree that MagLev should not be excluded from the list of contenders on an "assumed guilty" basis, we’re still waiting for some weighty arguments why MagLev is better. It’s not enough to state that MagLev is little or no more expensive than the alternatives. Can MagLev do a better job at lower cost? If not; forget about it! My impression that MagLev is sacred to the HiLoMag team has however been reinforced, with high-speed capability seemingly equally sacred, even if the freight market is sacrificed on its altar, as MagLev apparently only can be justified with the need for high speed.

Public transportation

I have read (reread actually) your description of a possible dualmode taxi-service with great interest as I have given the issue of public transportation in the dualmode era some consideration myself recently. What at first appears to be a straightforward proposal is infested with an incurable problem, I’m afraid. The problem is to provide chauffeurs at both ends of a fare. Most guideway access-points would need to have a shelter for chauffeurs and a great many chauffeurs would be needed waiting in these shelters for assignments.

In a traditional taxi the chauffeur stays in the car all the time, but only one chauffeur is needed per taxi. In your scheme two chauffeurs are needed to deliver a passenger to his destination, and as the destination is usually unknown prior to pick-up of the passenger there would have to be a chauffeur available at all potential guideway exits. Remember that if a dualmode taxi is ordered to a certain guideway exit it has to be assured that there will always be a chauffeur available to receive it at that exit. If that can’t be assured it would be necessary to redirect the taxi to a less convenient exit where a chauffeur can be made available. We could soon enough end up with a system where taxis are constantly being waived off and directed to other exits than originally planned. Only way to avoid this is to employ at least as many chauffeurs as for a traditional taxi-service, most of whom would spend their days in small shelters waiting for short fares.

This "chauffeur distribution" problem is even more severe and unsolvable than the much debated pallet distribution problem, and I believe HiLoMag would do better to abandon all ideas of dualmode taxis with chauffeurs jumping in and out of their cars or waiting in small shelters at guideway access points. It could do nothing to produce lower prices for customers, if indeed it could work at all.

Unfortunately your dualmode car rental idea won’t change much either. How do you obtain a dualmode rental car? Will it be brought to your door or will it be necessary to walk somewhere? If people will have to walk longer than a very short distance (as seems to be the case) your scheme will fail to attract users for the same reason why traditional public transit cannot attract them.

Anyway, car rental rates are not based on mileage alone, but on a mixture of duration and mileage with duration being the main contributor. If it was possible to hand the rental car back to the rental company as soon as you arrived at your destination wherever that would be, then we could reduce rates, as we would only pay for the time we actually use the car. That is unfortunately not possible with your scheme, as cars can only be returned to the rental company at certain locations (usually next to the guideways), thus your promised low rental rates will not materialize, and the market will not expand to any significant degree over today’s car rental market. Car rental companies sell their cars long before they are worn out anyway (when they can still get a good price for them), so longer lasting dualmode cars are not likely to have much positive influence on rental rates.

If you wish to add an innovative public transportation dimension to your HiLoMag concept a much better solution is available. A solution able to provide the services of rental cars, taxis, PRT-vehicles and even busses unhampered by the problems making your schemes impractical. This public transportation idea is described in my September 26th "Public Transit in the Dualmode Era" on these debate pages, and is available for everyone to "steal".


Last modified: October 16, 2000