Response to Schweizer's InTransSys Critique
February, 2000
I would like to take the time to reply to your recent critique of the Integrated Transportation System (InTranSys). The initial concept was developed before the first energy crisis of 1973, and was intended primarily to solve the problem of air pollution. At the time of the shortage, however, it became quite obvious that the need for a transportation system which was not dependent on petroleum was a far more significant reason for developing InTranSys. The 1973 oil crisis was entirely artificial, being orchestrated by the OPEC countries to free themselves from domination by the more developed nations. But today’s energy crisis – even though it has been completely ignored by government and industry throughout the world – is real. There is less petroleum available in the world today than there has been for hundreds of millions of years, the demand is higher than it has ever been before, and it continues to rise steadily. And the First Law of thermodynamics dictates that the exhaustion of this vital resource is both inevitable and imminent. It could not possibly be otherwise.
In 1974, I calculated when the world’s oil resources were most likely to be exhausted, and came up with the date 2018. Recent recalculations, plus similar ones conducted by many other scientists in the interim, have not changed that date significantly. This is because no new oil fields of global importance have been discovered since that time, and because new exploration techniques have allowed the world to be sufficiently thoroughly surveyed to assure us that none ever will. And when we do run out, there will not only be no oil left to propel our cars, but also none left for buses, trucks, tractors, motorcycles, power plants, airplanes, or ships.
I don’t know why you assumed that InTranSys was designed "just" for the purpose of carrying heavy freight. Its primary function is and will always be the transport of private automobiles, at least in the developed countries. But it required only a minimum of modification to allow it to carry public passenger vehicles and freight on the same track, thus producing enormous energy and financial savings for all three types of transport. Moreover, the fact which you cited about the ability to distribute most freight in smaller units has always been considered a major advantage of InTranSys. Today’s truckloads are overly large simply because of the practice of maximizing loads to minimize the driver’s wages. InTranSys will eliminate this cost and therefore greatly encourage the use of such small containers.
InTranSys was designed to carry even inseparable heavy loads because some of them do exist, and because the added cost of constructing the support system to carry them is insignificant. Your figures for the massiveness of InTranSys are greatly exaggerated. The T-piers are not 3m in diameter, but are instead 2m X 3m rectangular shapes with the material distributed near the corners and the center consisting of air. This design, developed by Figg Engineers, contains only a tiny fraction of the concrete and steel of a 3m diameter cylinder. In addition, the total width of a two-track line is only half of the 20m you cited, and virtually all of the land beneath it can be simultaneously used for other purposes.
The system can indeed transport 12,500 kg on a single carrier. Moreover, this 12,500 kg is almost all payload, unlike the case for today’s heavy trucks, which often outweigh their cargo. And yet this greater cargo load can be transported on a far lighter system (essentially a continuous string of bridges) than those in use today either for elevated tracks or highway bridges. The reason is as follows: today every freeway bridge must be designed to carry a static load of fully loaded trucks standing bumper-to-bumper (because of the inevitable traffic jams) filling each lane. The probability of this occurring is small, but the consequences on the few occasions when it might are so frightful that we cannot afford not to build them this way. But only two rows of such loads, one in each direction, is the maximum which could ever be carried on InTranSys, even though the line can transport the same amount of traffic as nine four-lane freeways. Thus a structure which is many times lighter can also carry many times more traffic.
You also mentioned that we don’t need InTranSys because freeways already exist. But they will be of no use in the future because none of the vehicles which now drive on them, whether they are cars, trucks, or buses, will be able to travel any appreciable distance under their own power when there is no longer any gasoline to fuel them. But the freeways can still serve a purpose. They will provide ideal rights-of-way for InTranSys lines. Moreover, one two-lane section of each one can still be left open to carry local traffic, freeing the rest of the wide corridor for purposes other than transportation.
InTranSys proposes the use of permanent magnets as the stationary members of the LSMs. This means that absolutely no energy is consumed during the relatively long periods when no vehicles are passing. Our original design was based on the use of barium ferrite magnets, which were already in common use at the time. Recent developments in rare earth ferrites, however, may change this. In any case the best option, from both an energy and economic standpoint, will be used.
The density of an InTranSys grid in any area will depend on the local traffic demand. It is likely to be densest in congested downtown areas (where it may be necessary to reduce the speed to 50 kph in order to build interchanges above street corners), and then less so as one moves outward through low-density commercial, urban residential, suburban, rural, and uninhabited areas. The latter, in fact, will be served solely by the high-speed intercity lines which traverse them. Thus there need never be any overbuilding of the lines.
A typical carrier designed for the support of private automobiles, urban buses, and light freight is expected to weigh less than 1000 kg., while heavy freight carriers are likely to be several hundred kg heavier. This is not really important, however, on a system employing LSMs and steel wheels on steel rails. Since the LSMs are used for braking and deceleration (both automatically regenerative) as well as for acceleration and normal travel, and since there is virtually no energy loss due to tire (or wheel) friction, flexing, or braking, the only important energy consumption factor comes from the inevitable need to overcome air resistance. All carriers have been designed to present a very small and streamlined cross-section, so the transport of the carriers themselves consumes very little energy compared to that of the loads they carry. Even smaller carriers will be used to carry such things as PRT vehicles, newspapers, and many other small cargo packets. And if you think that using such a carrier for transporting a single person in his own car is inefficient, just compare it with that same person driving his car. InTranSys can do the same job while expending only one-tenth as much energy under comparable conditions.
Control of an LSM-powered transportation system is the ultimate in simplicity when compared with any other alternative. Since the speed of every vehicle traveling within the entire network powered by a single grid of power plants is absolutely dictated by the frequency of the alternating current which is common to that entire grid, no vehicle can possibly travel faster or slower than any other. Moreover, the presence of a particular vehicle at any point between two interchanges (as well as the role of that leg in the overall track network) is but a single bit of information, while the direction that vehicle takes at each interchange is but another. These facts reduce the amount of information the computer must handle to just a tiny fraction of that needed for many very simple functions of a typical PC. Thus all of the information needed for the control computer to make its necessary decisions can easily be programmed into the computer and retrieved almost instantaneously.
Both the shortest (or the fastest) route between any two stations and the potential occupation of any vehicle-length site on the grid at any time can thus be easily calculated within microseconds, not milliseconds (it should be pointed out that such computer capability didn’t exist at the time InTranSys was conceived, but it has now caught up). Control computers will thus be so simple (and so cheap) that four of them will be used for each domain (as we call our control regions). Three of these will be used at once, with "voting" power held by each of them. Whenever one computer disagrees with the other two, it is retired from service, automatically replaced by the fourth, and a new one installed. If two vehicles happen to apply for routes which would cause them to occupy the same spot at the same time, one of them will be chosen at random to proceed, and the other will have to wait (in most cases only a fraction of a second) before it can commence its trip. The main computers for each domain will be designed to speak to each other in such a way that nearly all vehicles traveling from one domain to another can do so without delay (it should be remembered that those traveling long distances are most likely to have earlier priorities). When delays must occur at a domain boundary, it is never likely to last longer than a second or so, and can easily be planned in advance.
Just try to compare this capability with that of a system employing any other means of propulsion. Linear induction motors (LIMs), which require separate and unrelated methods of controlling speed, and which are subject to unpredictable speed changes from things as minor as a patch of snow or a gust of wind, are not likely to be capable of handling even 10% of the amount of traffic as InTranSys. And even at that dispersed spacing, they will still not be nearly as safe. Only LSM-powered systems, which possess both the power and the response capability to overcome such contingencies, are essentially immune from such events. As for "high power semiconductors" burning out at critical times, the acceleration of vehicles onto the system will be based instead on precision timers based on the AC frequency. Again redundancy can reduce the probability of serious consequences due to the untimely failure of such elements to the vanishing point.
The kind of track blockage you cite fits the description of the third, most critical, and least likely of the three levels of emergency operation which (along with the means of handling them) are all well detailed in the Control section of the Technical Report appended to our website. There are two ways in which vehicles heading for the blocked section can be rerouted in advance. The most capacious (and therefore the preferable) of these is to divert the vehicles onto other legs of the track grid, where they can be shunted off the system at any one of a number of stations downtrack, where they will remain until they can resume their journeys later. Shunting vehicles off at stations uptrack from the last interchange before the accident site is only a secondary means of solving the impasse. It will also be utilized, but its limited storage capacity means that only a few vehicles can use it. By contrast, we know that there will always be room for a vehicle to enter downtrack legs of the system, at least as far as the next station and the next interchange, and in most cases much further.
We also have provisions for those vehicles which cannot follow either path to continue along their originally designated route past the initial interchange and then come to a controlled stop before the accident site is reached (a small onboard computer will control its braking). It is the enormous capacity of InTranSys (which you criticized earlier) which provides for this possibility. Such vehicles must remain on the track until they can be moved at a slow speed, either forward if the stoppage can be quickly removed, or backward if it cannot. All of these vehicles will also be shunted off at the next available station, to resume their journeys from that point. The resumption of a journey requires no action by the vehicles’ passengers. Another computer (separate from the control computer) maintains a continuing record of the location and destination of each vehicle, and can automatically restart the trip whenever other traffic allows it (usually a matter of seconds). Even freight can be rerouted using this method, although heavy loads must do it from a freight stations.
Moving uptrack from the site of the blockage, the ease of rerouting other vehicles which were originally destined to use the blocked section becomes ever greater. As soon as any blockage of a particular section of track occurs, a signal will be fed back to the control computer and the blocked section will be removed from the grid of potential routes. The routing of every vehicle which would otherwise passed through that section will be recalculated. It may even be possible to reroute some vehicles in transit. But all of them can quickly be shunted off to a station and then restarted from there. Thus the probability of even one additional section of track having to be closed is extremely remote (again because of InTranSys’ high capacity). Therefore the scenario you described of deadlocking the entire network would be impossible unless a significant fraction of all the world’s traffic should suddenly try to go to the same place at the same instant.
When one compares the handling of this worst-case scenario for InTranSys with comparable incidents on any other transportation system (including our present one), we find that (a) such occurrences would be far less likely, (b) resolving the situation afterward would be much simpler, and (c) the consequences of the incident would be far milder than on any of the less capacious and less precisely controlled alternatives.
You have also hinted more than once that, since the original concept for InTranSys was developed in 1970, it must necessarily be obsolete by now. But the only thing that this early date really proves is that at the time when we started working on it, our thinking was fifty years ahead of anyone else’s, whereas today we are only 20 years ahead.
Last modified: February 17, 2000
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