Palleted Dualmode IS an Answer
Van Metre Lund
Criticisms of palleted systems have made certain assumptions about how such systems would need to be constructed. I can understand how these assumptions may have been made and do not suggest that they were made purposely, but do want to point out that the criticisms do not apply to properly constructed palleted systems.
Before doing so, I suggest that we all keep in mind that we do face a very serious immediate problem with autos. Their use, which is expected to be increasing every year for years to come, is depleting irreplaceable oil resources at an alarming rate, causing deaths, injuries and property damage that could be avoided, polluting atmosphere and tying up traffic. Non-palleted dualmode systems, called "true" dualmode systems by their supporters, do not appear to be likely to even start helping with this very serious problem for many years.
Proposed palleted systems include my Autran system (www.autrancorp.com), the InTranSys system, the MegaRail system and others. In my Autran system, a pallet (or what I have referred to as a "platform") is supported from below by a carrier vehicle which moves within a narrow generally tubular guideway. The InTranSys system includes auto-carrying pallets suspended from carrier vehicles in an elevated guideway. In the MegaRail system, a pair of enclosed guideway rails are spaced apart a distance greater than the width of an auto to be carried and provide support for rubber-tired wheels of a ferry structure which operates as a pallet to support an auto.
Any of these proposed palleted systems might be constructed in a relatively short time and then start to carry almost all types of existing autos, thereby immediately dealing with the serious problem of auto use Moreover, there is considerable hope that one or more might be constructed in the near future since they might operate profitably and require no taxpayer support. An Autran financial analysis that a 10 mile system which only carries autos can yield a net income equal to 12.2% of capital costs of $75.7 million. InTranSys and MegaRail supply little in the way of detailed figures but InTranSys might also provide a profitable auto-only system and MegaRail claims that no tax funds are required. I believe that my Autran system has important advantages over both the InTranSys and MegaRail systems but they do not appear to be germane to this discussion. I will however discuss a 10 mile Autran system in some detail because I believe it to be a good example of a properly constructed system to which criticisms that have been made of palleted systems do not apply.
The 10 mile or 16 km Autran system includes ramps leading to two loading and two unloading stations in each direction with an average of 12 lanes per station, e.g. 16 lanes in each end station and 8 lanes in each of the two intermediate stations. Each 16 lane station will cover an area of less than about 16000 m2 or 4 acres; each 8 lane station will cover an area about half as large. [To view a station design that covers 8 acres, click here]
Obtaining areas for stations in crowed urban areas has been mentioned as a problem. However, the system is not intended for crowded urban areas which might more appropriately be served by PRT systems. The system is intended for interconnecting suburbs and cities and for installation in other places in which obtaining 4 acres of space should not present a serious problem. Also, each station is elevated and provides a covered space that might be used for a shopping center or other purposes.
The handling of pallets has been asserted to be a serious problem, under the assumption that entry and exit facilities must be located in connection with each other, under the assumption that it must be possible to provide pallet storage areas to and from which pallets must be moved and under the assumption that storage areas must be provided for carrier vehicles separate from pallet storage areas.
None of these three assumptions applies to the Autran system in which the entry and exit facilities are completely separate, there are no pallet storage areas as such and no separate vehicle storage areas. At all times, each of the 422 carrier vehicles together with an associated one of the 422 pallets is either in a loading position of a loading lane, in a queue ahead of loading position, in transit from a loading station to an unloading station, in transit from an unloading station to a queue of a loading station (usually the queue of the nearest loading station) or, in certain circumstances, in transit from the queue of one loading station to a queue of another loading station that has less than a certain minimum number of vehicles and associated pallets therein.
For example, in a completely inactive condition of the system, 48 carrier vehicles and associated pallets may be in loading positions, 240 may be queues for such loading positions 90 may be in queues ahead of the two 16 lane loading stations and 44 may be in queues ahead of the two 8 lane loading stations. Each 16 lane loading station can load 48 pallets per minute or 1.2 per second. Consider an extreme case in which users start to arrive at one of the 16 lane loading stations at a rate equal to or greater than 1.2 per second and continue to do so indefinitely. All of the 16 loading positions and 165 associated queue positions could be emptied in about 150 seconds or 2.5 minutes. However, after 20 seconds, the number in the queue positions will drop by 24 from 165 to 141. At that time, vehicles with empty pallets may be programmed to start moving from a nearest opposite direction loading station 7 miles away, reaching the loading station in about 420 seconds, about 400 seconds or 6.67 minutes after the loading station is emptied. This delay time is a temporary hiatus that only occurs once in this scenario. Once ended, pallets can be loaded indefinitely at the 1.2 second rate. While not ideal, a temporary hiatus of 6.67 minutes that can occur only in the most extreme condition is not considered to be a serious problem. Patrons frequently wait much longer times in parking garages.
Note also that if delays are occurring while use of the system continues to be high, it means a very desirable situation in which demand is high and high profits are being made. It is not a time for throwing up hands in dismay. The thing to do is to consider raising fares, or adding more pallets and carrier vehicles and/or more loading and unloading lanes to enjoy still higher profits. Note that less than half of the available guideway capacity is used in the system being analyzed, that the 422 carrier vehicles and 422 pallets represent about 8% of total capital costs and that the 96 loading and unloading lanes represent about 19% of total capital costs. If guideway capacity is reached and demand is still not being satisfied, the thing to do is to consider building an additional system that may reduce some of the demand for the existing system.
Details of loading and unloading lanes, pallets/platforms, carrier vehicles and other components of the Autran system are provided atwww.autrancorp.com, also a detailed financial analysis and analyses of potential advantages.
In conclusion, palleted systems can not only be viable from a financial standpoint, but can be immediately effective in dealing with the problems of auto use. I submit that a thorough study will show that they should be seriously considered for implementation at the earliest possible time.
Last modified: September 08, 2000