by Francis D. Reynolds
On Oct. 16, 2000 Kim Goltermann gave us a debate contribution titled, Reaction to "Dualmode System Design Odds and Ends". I regret that I was too busy to respond to his comments at that time. Below in 10-point italics are selections from Kim's article, followed by my comments in 12-point.
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" Im not thinking of vehicle mounted mechanical devices, but of a guideway mounted preferably non-mechanical switch.
The Morgantown West Virginia driverless "People Mover" system, which I helped to design, actually steers pneumatic-tired wheels of the cars much as human drivers steer. Except instead of human eyeballs judging where the side of the road and the turns are, the Morgantown cars have an arm on each side that senses either one guideway sidewall or the other guideway wall. The resulting light force is amplified in a "power-steering" servo system to steer the wheels. As Kim observes, Morgantown, which is still operating daily, is not a high-speed system, but if it were that now-old automatic steering system could do a far better steering job than human drivers do at high speeds. I can't personally take credit for that steering system, by the way.
The system proposed for HiLoMag is the same basic guideway-sensing concept as Morgantown, but is maglev so that there is no wear or mechanical noise generated, and the guide rails are located flush with the surface in the center of the guideway instead of in guideway sidewalls. And in maglev HiLoMag there would be no wheels to steer, blow out, wear out, or slip (except in the street mode after delevitation).
We claim that switching from within the cars will be quite easy, while safe independent switching of closely spaced high-speed cars by guideway switching actions would be very difficult if not impossible. The proposed minimum headway between HiLoMag cars at 200 mph is only 0.054 seconds (for 15-foot cars and one foot clearance). With the switch in the guideways each switch would have to receive and act upon up to nineteen switching commands every second, with no time for redundant commands or any kind of checking. And the commands would have to be precisely synchronized with the arrival of each high-speed car at the junction.
This would appear to be an impossible job with mechanical guideway switching. And I have seen no way of accomplishing independent "guideway-mounted nonmechanical switching" of closely spaced high-speed cars. If someone has a promising concept for such a system I would be very interested in seeing it.
In the HiLoMag concept the guidance and switching subsystem uses inductive maglev guide rails and in-car switching as shown in the guidance and switching section of
Some readers might wish to review that reference in order to better understand the following.
With in-car switching the commands would be individually sent to the cars far in advance of their arrival at the junctions. This would allow plenty of time to send duplicate commands if desired, and to receive an automatic confirmation from each car while there is still time to correct any errors. In fact, the switching commands might be stored in memory in each car for its entire trip, but this would require updating of that memory if there are any changes of plan en route. For redundancy one might even use a combination of guideway-computer switching commands and onboard memory.
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." 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.
The misunderstanding here is that my sketch that shows "guideways split into two" in the reference was intended to show only the switching concept, not other parts of the guideway system. The arms seen branching off from the main guideway would be of three different kinds. First, they could be the origins of additional synchronous guideways (branches from a trunk). Cars switching to a start-up branch guideway (that will have no other traffic to contend with) would continue at synchronous speed.
The second kind of exiting arms are transfers to other through guideways that already carry traffic. In that case the arms shown are ramps in which the computer will control the speed of the transferring vehicles in order to properly merge them with the traffic on the guideways they are entering, or abort the merges if necessary due to excessive traffic. Remember that HiLoMag has synchronous guideways but asynchronous ramps. Only the ramps are controlled. The guideways per se are always at full velocity and are oblivious to the LSM cars riding some of their constant magnetic waves, except for the changes in guideway current that the cars cause.
The third kind of exiting arms are exit ramps from the guideway system back to the streets or highways. Arms of this third kind will automatically decelerate and stop the cars that enter them. Then the human drivers will merge their cars with the traffic on the adjacent streets or highways.
A misrouted car might be kept on the guideway it was scheduled to leave. There it could cause no damage because it would continue to occupy the spot it had been occupying, and the computer would know that it was still there and would not try to merge another car into that spot later. Or the misguided car may unintentionally enter a ramp to another guideway or exit. There the computer would treat it exactly like a car that was intended to merge with that guideway, and the car would either be merged safely (on a guideway it didn't want) or the merge would be aborted for lack of space on the receiving guideway.
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.
HiLoMag would welcome all of the routine freight that customers wanted to put on it, but perishable-freight shippers, like impatient human passengers, would be the most willing to pay for the high-speed that can be offered by the guideways. Remember that aerodynamic drag varies as the square of the velocity. Jet airliners fly high, in air of greatly reduced density, in order to reduce the drag. We won't be putting our guideways in evacuated tubes for a while yet.
So higher-speed vehicles mean a lot higher energy costs, even with efficient electric guideways. Slow-running freight trains will therefore still be able to offer lower ton-mile freight rates. Railroads can run different types of trains at different speeds on the same tracks. LSM guideways, as I have seen them, would always run at the same high speed. But conceivably we could reduce their speed for a few early-morning hours in order to attract cheap unmanned freight business, carrying ore, coal, and other low-cost non-perishables.
But I too am concerned over polluting fossil-fuel-burning vehicles. The sooner we can get diesel trucks off the highways and diesel locomotives replaced with electric locomotives the better. And getting most of the IC private cars off of the highways and onto electric guideways will save by far the most petroleum and reduce pollution the most. But we need to be realistic. As we are aware, there is now barely enough electrical generation in much of the United States, for one example, to keep the lights lit. It will be a long time before we will have ample environmentally clean electricity, all from renewable-energy, for all purposes including the new guideways.
GUIDEWAY FREIGHT CAPACITY
As proposed in my recent "Operation and Control with LSM" article, let's use two standard sizes of vehicle cross section, and several standard vehicle lengths. Then we could put fair-sized buses and sizable "magtainers" on the guideways that would carry a lot of freight. However, I don't think it would be cost effective or politically expedient to try to build guideways big and heavy enough to carry railroad-freight-car size loads. And we would still need the railroads to carry huge oversized loads.
Many of the types of products that are now shipped by the big rigs on the highways would continue to travel there. But they would get there much faster than they now do, because the highways would no longer be crowdedmost of their present traffic would be on the guideways.
However, guideway freight would not only be faster than trains and highway rigs, it will be faster than airfreight up to moderate distances. It would take a lot of domestic airfreight business away from the airlines, just as the guideways would take a lot of domestic passenger business away from the airlines. Good. People living around airports hate airplanes. And airplanes use a lot of increasingly precious fossil fuel and produce a lot of CO2, smog, and other pollutants. Unlike for ground vehicles, there are no satisfactory alternate fuels or other energy sources for airplanes. Long extension cords are out.
Last modified: August 04, 2001