Pallets Revisited and Other Dualmode Comments
by Kim Goltermann
It has been a while since last time I contributed anything to these pages, in no small part because Ive been compelled for various reasons to pursue other interests. Nevertheless, I have not been completely idle in respect to the dualmode cause. Especially the many and varied problems involved in getting from our present deficient transport infrastructure to a more convenient and able dualmode future have caught my imagination and in turn also shaped my perception of what would be the best approach concerning a future dualmode transportation system.
John Hopkins raises many of the problems in his latest contribution and, sadly, the problems are real enough. I will therefore devote the last part of this commentary, not to a rebuttal of the problems as lined up by John Hopkins, but to a short presentation of ideas and strategies that could be helpful in overcoming at least some of the obstacles.
In the meantime will I concern myself with William Turnbulls proposal for a dualmode system. It will come as no surprise to many regular posters or readers here, that Im at odds with especially two ideas included in his proposal: 1) The use of car-ferries (pallets) rather than cars with dualmode systems integral in the vehicle (true dualmode cars). 2) The use of packets (with mechanical couplings) as opposed to single-vehicle operations utilizing a so-called Clear Path operational control principle. I will therefore seek to counter some of Mr. Turnbulls claims in the following, undoubtedly flogging the same old horse on a number of counts, but hopefully also providing a few new arguments as well.
Pallet Vehicles vs. True Dualmode Vehicles
In order not to merely repeat the many pros and cons that have already been repeatedly brought up by me and others will I jump directly to some of the reasons Mr. Turnbull mention, which in his opinion favors the pallet vehicle solution. These are in no particular order:
The condition of a true dualmode vehicle is unknown when it requests entry to the guideway system and theres no simple (quick and cheap) way to diagnose said condition before entry, whereas a pallet vehicles condition can be continually (or periodically) monitored, thereby largely preventing mechanical breakdowns during use.
The cost of providing a number of specialized carrying vehicles will, all things considered, be on par with or lower than providing the necessary features integral in all and every car that potentially will use the system.
The eternal dilemma: What came first? The chicken or the egg? A system operating car-ferries captive on the guideway will provide for all the requirements of customers/users from day one, whereas a true dualmode system will have to wait years before the number of customers attains the critical mass needed to warrant the enormous investment.
Mr. Turnbull claims that a pallet has an advantage over a true dualmode vehicle insofar it never leaves the guideways and its condition therefore will be better known, whereas we would have to assume that a true dualmode car requesting entry to the guideways could have any number of potentially disastrous defects. So what?.....we still dont know with any certainty the condition of the pallet and would have to assume it could have equally disastrous defects, unless we continually monitor (or frequently check) everything of relevance.
If we can monitor or check it on a pallet vehicle what would prevent us from doing the same on a true dualmode car, either continually or prior to entry? Its the condition at the time of use that is relevant and THAT can be verified with equal ease for pallet vehicles as well as true dualmode vehicles. Events taking place between guideway use are utterly irrelevant from a system point of view, whether the vehicles in question are stored in a controlled environment or are also used on the regular road network between guideway trips, as long as the condition is checked prior to (or continually while in) guideway use.
A pallet vehicle is supposed to be in intensive use and should it develop a defect (as it is likely to do when in constant use, whether itll be sooner or later) we are facing a 100% certainty it will happen WHILE ON the guideway, whereas true dualmode vehicles could develop defects, have them identified and corrected BEFORE entering the guideway system. This is actually the most likely scenario since the regular roads are likely to be much harsher on a car than will the guideways, thus any defect will likely occur during regular road use. The regular roads can even be considered a rigorous, continuos real-time test of vehicles; the outcome of which will be assessed prior to each guideway entry.
Immediate and automated diagnostics of a true dualmode cars condition at the authority of one or more computers IS perfectly viable. Thats the main point and to claim otherwise is out of bounds with realities. Many new cars already have most of the features. A computer assesses when regular service is due, brakes are often monitored by a computer, the entire engine is controlled and monitored likewise. Transmissions often have various computer programs one can choose from. A system monitoring the tires (including real-time pressure, wear and tear) is available as an extra on some luxury cars and will probably soon go the way of ABS-brakes, Electronic Stability Programs or Airbags and become standard items on even the cheapest models.
In short, everything in a car can be controlled and monitored by computers, always providing a real-time picture of the vehicles condition. All we need is to define which parameters are essential (or just relevant) in respect to guideway use and make certain these are rigorously monitored and upheld.
The second of Mr. Turnbulls claims I will take issue with here is the question of comparative costs of the two types of systems. Let me first make it clear that I envision a system where true dualmode vehicles will not deviate much conceptually from the cars we already buy and drive. This means that the changes will be few and the additional expenses arising from these changes will be small once the true dualmode cars are put into mass-production.The type of palleted dualmode system favoured by Mr. Turnbull is a high capacity system. A few simple calculations reveal that there would be approximately 100 cars per mile of guideway if it was utilized to 50% of theoretical capacity. This means that a system composed of 100 miles of guideway would need 10,000 pallet vehicles at 50% utilization. Add to this pallets needed as buffers at entry points, empty pallets being rerouted, pallets held in reserve to counter abnormalities and inoperable pallets awaiting repair. Were now looking at 15.000 pallet vehicles or more just in order to utilize 50% of our 100 mile guideway grid.
Of course the system operator would have to provide and maintain all these vehicles (Ill come back to that), but try for a minute to imagine where to store all these vehicles when traffic is slow and most of them therefore will stand idle. They are captive to the guideway and parking on the guideways carrying traffic is not an option, nor is parking on the entry/exit ramps. If each pallet is 20ft long (a reasonable assumption?) we would need (15,000 x 20ft/5280ft) almost 57 miles of storage guideway. These 57 miles of storage guideway will not earn the system any revenue, but will nevertheless have to be built and they are unlikely to be any cheaper per mile than the revenue earning guideways. And, what if you want to utilize, say, 75% of the systems theoretical capacity? Well, add another 5000 vehicles (at least) and another 19 miles of storage guideway.
If using the 75% utilization example, a palleted dualmode operator would have to provide 100 miles of guideway + entry/exit ramps + 76 miles of storage guideway + at least 20,000 pallet vehicles, whereas a true dualmode operator would only be required to provide 100 miles of guideway + entry/exit ramps and could still attain as high an utilization of the guideways as is practically possible.
Speaking of the pallet vehicles, all of the 15,000 to 20,000 pallets each constitute a complete and autonomous entity with wheels and brakes, suspension and propulsion system, guideway shifting mechanism, coupling devices, sensors, back-up power source, clamps to fasten the load (car), communication systems, computers, maybe even AI and what more do we have? Furthermore, they will have to be of a rugged design since they are supposed to be in more or less continuos use, indicating they will have to be heavy and therefore in a sense overengineered. These vehicles will have to be produced by someone and since that someone is not pushing out millions of vehicles as are car manufacturers, but only multiple thousands, will the price per unit be much higher, especially considering the complexity of the vehicles in question?
Furthermore, the producers of pallet vehicles will most likely NOT be subjected to the same fierce competition as exists between car manufacturers, thus there will be little motivation to rationalize production of pallet vehicles and cut costs. A pallet vehicle manufacturer will simply demand the production price whatever that happens to be plus a profit, which will most likely be high if the pallet vehicles development costs are to be recouped on a much smaller number of vehicles. Dont be surprised if ONE pallet vehicle will cost 10 times more than than ONE normal car as we know cars today. Experience from the railroad industry indicates thats what we would have to expect. NOTHING beats high numbers in reducing production costs and if we enter the market of consumer goods (true dualmode cars would be consumer goods) this mechanism becomes even more apparent.
Pallet vehicles on the other hand will never be built in the same numbers and can never be considered consumer goods. They will however be used by ordinary travelers (consumers) and the higher prices of the vehicles will eventually be paid by consumers. Consumers that will have to buy their own car to access the system anyway. Now, wheres the logic in that? The palleted dualmode proponents most common argument in favour of pallets is the what came first, the chicken or the egg? dilemma. The argument postulates that pallets will ensure that there will be plenty of paying customers already on opening day, whereas a true dualmode operator would face the problem that no one has bought the special true dualmode cars yet.
On the face of it, that argument seems valid, and the pallet proponents often use the argument to sell the down-sides/disadvantages that pallets undeniably also have, but lets examine how relevant the argument really is. Theres a few things a true dualmode operator can do to alleviate the chicken or egg dilemma. First, true dualmode cars could be offered for sale a couple of years prior to opening day which would persuade at least some customers to buy a dualmode car in anticipation of the advantages that will become apparent when the guideways open. The system operator could also make agreements with freight forwarders (vans?), taxi companies and transit operators (mini-busses?) that they will buy some vehicles up front and put them in operation on opening day. Of cause, these initiatives could only ensure that the number of potential customers would initially be FEW rather than ZERO.
Next, well consider the wide disparity between the investments a palleted dualmode operator and a true dualmode operator is required to make before they are ready for business. If we use my example from above, well see that a palleted dualmode operator with 100 miles of guideways will be required to provide some 57 to 76 extra miles of storage guideway and 15,000 to 20,000 expensive specialized vehicles that a true dualmode operator would not need to acquire. These extra items/systems represent a SUBSTANTIAL investment. It is therefore prudent to say that a true dualmode operator will most likely be financially more robust when considering the full market potential (realized when everyone has true dualmode cars) in relation to the investment made and will therefore also be able to operate with a payback formula where the debts will continue to grow during the first, say, 5 years of operations simply because revenues will be insufficient to start repaying the debts (possibly even insufficient to cover operating costs).
There are actually plenty of examples of just that in the real world, e.g. a bridge operating company has seen its debts continue to grow for its bridge between Copenhagen (Denmark) and Malmö (Sweden), due to insufficient paying customers during the first three years of operation. Since the investment for the true dualmode operator would be significantly smaller than for the palleted dualmode operator the situation would reverse after a number years. As normal cars will (likely) be replaced by dualmode cars at a rate of between 6% and 10% annually, its likely that reversed situation will occur well before the ten year mark and from there the true dualmode system will be in a much more favourable financial situation than the palleted dualmode system. The only important thing is that the financial payback model anticipate the situation from the beginning; the rest is trivial.
Another of Mr. Turnbulls arguments is the notion that a palleted dualmode system could eventually be developed into a true dualmode system. Not likely, because if the hardware was amendable to true dualmode operations it would be much more attractive to provide that option from the onset, saving the investment in at least some of the pallets and storage guideways. It is on the other hand entirely possible to provide pallets supplementing a true dualmode system as a temporary measure to overcome what remains of the chicken or egg dilemma until such time that most cars have integral dualmode compatibility, and these temporary pallets would even have advantages in that they might be able to leave the guideway for loading/unloading/storage detached from the system.
With a palleted system you are stuck with pallets and will eventually have to initiate a completely new system should true dualmode some day be deemed more desirable for any number of reasons. At least that pertains to all pallet using systems/concepts I have seen.
Packets or single-vehicle operation?
Before commencing my critique of Mr. Turnbulls operational concept I ought to mention that Im indebted to him for coining the term Multiple Slot Clear Path operational control. I havent seen the term used before, but I knew what it was, even knew thats what I favour....I just couldnt put words to it. Also the idea of Quota Allocation is one I favour (but Ill return to that). I have no reason to doubt Mr. Turnbulls calculations , but its noteworthy that he doesnt provide any comparable calculations for a single-vehicle operating (Multiple Slot) Clear Path system. Those few figures he does provide in that respect are over-simplified and don't provide any foundation for fair comparisons. Furthermore, I find the described operational concept overly complicated for no apparent gain, in turn depending on a multitude of empirical data (which are not readily available) in order to function in an optimal manner.
But now to my main reservations: Exiting a car from the front of a 20-25 vehicle packet, transferring it to another line and letting it reenter at the back of another 20-25 vehicle packet is the equivalent of letting a vehicle on a Multiple Slot Clear Path system slip 20-25 slots during the same type of line transfer. If we introduce a Multiple Slot Clear Path system where each car has as much as 20 alternative slots to choose from when transferring at junctions, Id say there would be no problem finding a vacant slot even when operating near theoretically full capacity. We would have 98.85% chance of finding at least one vacant slot at 80% utilization and would have 20 slots to choose from. Seen in that light I find it hard to point to any advantage at all of introducing packets.
Another way to see things is to consider the two operational principles essentially the same. Mr. Turnbulls system would have one packet every 3-5 seconds while my system would have many more packets much more frequently, in the order of 3-5 per second. Mr. Turnbulls packets can have a value (number of vehicles) ranging from ZERO up to 20 or 25. My packets will either have the value ZERO or ONE. The system using large packets will attain its flexibility and avoidance of unsolvable conflicts from the fact that each packet can have any of a wide range of values, but preferably not the maximum figure. My smaller packets will very frequently have the maximum value of ONE, but will fully compensate for this as vehicles can jump from a packet to a preceding or following packet (if vacant) whenever needed; during line transfers will it even be possible to jump several/many packets up or down.
My system would have the full flexibility of Mr. Turnbulls system with the added benefit that potentially unsolvable conflicts are in fact pre-empted by delaying entry to the system a few seconds for any given vehicle. Bottom line: Theres hardly any difference, certainly none warranting the complications involved in physically coupling and de-coupling vehicles at speed.
Slot Slipping or Advancing
Returning briefly to the issue of slot slipping or slot advancing, I dont see any need for a system providing 20 optional slots at every junction. The figures I have been using indicate that 3-5 alternative slots will be plenty, especially if coupled with Quota Allocation. As Mr. Turnbull so rightly observes, entering traffic in a Clear Path system will have a tendency to monopolize the guideway use further downstream, thereby possibly preventing other vehicles from entering the system. This can be reduced, maybe practically eliminated, if a Quota Allocation algorithm is introduced that will delay upstream entry slightly every time the traffic threatens to monopolize downstream usage too much.
The difference between the way I would apply Quota Allocation and the way Mr. Turnbull sees it is that in his system is it an essential building block, whereas I consider it an upgrade or optimization option. We dont need to develop (and pay for) such an upgrade up front, but can introduce it whenever theres an obvious (empirically established) need for it. Furthermore, I see no obvious limit to how much refinement can eventually be built into such a Quota Allocation function, given theres a need for such refinement.
To summarize: I dont see much difference in capability between a packet operating and a single-vehicle operating control principle. The large apparent difference demonstrated in Mr. Turnbulls calculations only stands out because he compares apples and oranges. A simplistic rigid Clear Path system is not the same as a Multiple Slot Clear Path system applying refined measures to pre-empt bottlenecks. The only visible difference inherent in Mr. Turnbulls proposal is the obvious disadvantage of having to couple individual vehicles into trains.
Can we get from here to there?
The August 14th, 2002 contribution from John Hopkins is depressing to read, but is also necessary to read. Its depressing to read because the obstacles to a successful outcome for the dualmode idea most of us feel so passionate about appears almost insurmountable. Its necessary to read because as most of us are painfully aware most of those obstacles are real and if not completely insurmountable then they are, at least, very hard to overcome.
I have already shared some ideas on how the implementation of a true dualmode system could be enhanced by adopting certain choices and policies in my contribution of January 25th, 2001 Implementing True Dualmode: Can it be Done? While I feel these ideas and observations are still valid, I also feel it is necessary to add a few things that have only recently dawned upon me. First, it will be very difficult to implement the ultimate high-speed, extremely high capacity, MagLev supported, can-do-all dualmode system from the very outset, simply because the development challenge is so enormous, both in terms of money and time needed, that the gamble becomes too big. The auto industry is not geared to produce vehicles very different from the current ones. Therefore, I suggest the adoption of a policy of making incremental improvements and upgrades, which will eventually result in the kind of ultimate dualmode system that, among others, Francis Reynolds and myself advocate. I suggest a new dualmode system should take off from where the Automated Highway System (AHS) program landed, building on its successes but improving upon its shortcomings.
These improvements could include complete segregation from other traffic on a guideway, a system guaranteed to prevent derailment and possibly a different traffic management philosophy. Once this redeveloped AHS system is up and running, it will be time to consider an upgrade, which could include electrification (adding electric motors in newly-built cars) and operation at shorter headways. The important thing here is that the cars built for the new system will also be able to run on those guideways already built. Backwards compatibility must be maintained.. Its not entirely impossible that the old dualmode cars will also be able to run on (not utilizing the electrification) the new guideways, maybe after a minor computer upgrade.
A third step could be more safety and even shorter headways, possibly the introduction of a linear propulsion system (LIM or LSM). Again, new cars would be able to utilize all the old guideways, although this time it will be very difficult to upgrade old cars to the new guideways. A fourth step could be the introduction of MagLev for high-speed applications and who knows what the fifth step could be? The main idea is to choose a system that is amendable to all these upgrades without making the older variants completely obsolete overnight, always ensuring compatibility with existing guideways.
I believe its possible to design such a system and it would ensure that we could begin with a modest step forward without foregoing the option of the ultimate system at a later date. Moreover, I believe most dualmode developers are trying to sell the idea to the wrong people. We have heard calls for a dualmode tzar; many developers and inventors have spent countless hours trying to explain their wonderful ideas to skeptical politicians. But politicians and other political decision-makers have very little development money to spend on visionary projects and ideas. The political establishment is much more likely to pour huge sums into tested and traditional technologies making little or no impact on the problems than pour much less money into a vision that potentially could solve all problems.Forget about politics and politicians for now! Sell the promise of huge markets and a prosperous future for the auto industry instead.
Involve the Auto Industry
The auto industry will happily buy into that promise the same way the railroad industry bought into it in the 19th century and the same way the very same industry bought into it during the latter half of the 20th century. The auto industry will sell the idea of dualmode to the political establishment by its own initiative once the prospect of large profits and continued expansion makes an appearance. We, the early dualmode enthusiasts wouldnt be required to lift a finger. The car manufacturers make profits from building cars. They would enthusiastically make the switch to building dualmode cars if therere good prospects they can sell more cars and make bigger profits by doing so. Car manufacturers already spend billions developing new models in the hope they can increase their share of the market a little bit. A billion or two spent developing a practical and marketable dualmode system would do far more to safeguard and/or increase a car manufacturers future profits than would a few handfuls of new but ordinary car models.
The first on the market will have an immense advantage by securing a large share (initially 100%) of the dualmode market, just as the company developing the system (owning a decent share of the patents) would probably be able to demand license payments from its competitors. Any chief executive would consider that a sweet scenario! Also consider, its the auto industry that has the experience developing, producing and marketing the most successful, mass-produced transport solutions the world has ever seen. The car manufacturers have huge research and development facilities; they have thousands of engineers and work with many sub-contracting firms developing related technologies too and they have the development money.
In short, the auto industry is the one that can pull the dualmode idea to the fore; trying to bypass it in the development phase would be counter-productive, even self-defeating. Furthermore, the auto industry has demonstrated that it can reach agreement on universal standards up front rather than adopting them on the fly. The new, still to come standard 42V electrical system planned for future cars is an example how the industry can agree on a standard BEFORE it is even introduced into production. The same kind of agreement would obviously be needed between at least a couple of the big players before any dualmode standard was finalized, but it doesnt appear to be unrealistic given previous agreements.
Another advantage of relying on the car manufacturing industry as the main stakeholder in the dualmode project is their truly global outlook. Should a potential deal fall through with the politicians of Boston or Rome will they just turn to the politicians of Sydney, Paris or Kuala Lumpur instead. No single city, region or nation will have a veto whether dualmode will be implemented or not. Lastly, speaking of the political level; traffic planners and elected officials are becoming increasingly desperate. They want transportation solutions that work but cant find any. This desperation was readily exposed about a year ago here in Copenhagen when an ordinary citizen proposed (in an open newspaper letter) that a system of modern street-cars (trams) could solve many of the citys traffic problems. Immediately many politicians and professional traffic managers/planners jumped at the opportunity and supported the idea as if some new revolutionary type of street-car had emerged.
In fact it was more or less a proposal to reintroduce the same type of street-cars the city abandoned in 1972, and the support it gathered (and still holds) can hardly be seen as anything but an expression of sheer desperation. In my belief this sense of desperation indicates we can likely expect a significant snow-ball effect should we ever succeed in getting a dualmode system into operation somewhere in the world. Just ONE system demonstrating its worth will virtually guarantee dozens if not hundreds of large cities lining up to buy the next system. Overly optimistic? Perhaps, but the desperation is evidently there and will only grow until released. Billions are poured into systems that have little or no alleviating effect, for the sole purpose that decision-makers have a need to demonstrate an ability to "do something".
Last modified: September 12, 2002