Rebuttal to "Personal Rapid Transit — Cyberspace Dream By Bill Wilde This article is a wonderful contribution to the PRT debate. In one place thecritics have given it their best shot. Henceforth when one needs to present thecase against PRT this single reference will suffice. Nobody’s ever done itbetter, or is likely to. One of the first questions about the article is its authorship. Who wroteit? Who is on the team that approved it? Why don’t their names appearunder the title? The team doth protest too much, methinks. One wonders why. Why does theelephant fear the mouse? According to the 2002 National Transit Database, U.S.transit spent $36.5 billion in capital and operating funds in 2002. Taxi 2000Corporation is seeking $24 million to fund a multi-year Product CertificationFacility (PCF), less than seven one-hundredths of one percent of this amount. Development funding is being sought from private and public investors. Is thismeager amount such a threat to the established interests? Especially since theteam concludes that PRT is wholly impractical, is fundamentally flawed, andcould never work. Why fear that which could never hurt you? In discussing PRT, the parties must begin by agreeing on what PRT is and whatit is not. This has confused the debate for decades. The Advanced TransitAssociation defines PRT as having the following characteristics:
This definition is consistent with that in U.S. Congressional Office ofTechnology Assessment’s "Automated Guideway Transit" report of1975. Thus when the article discusses "the AirTrans system at Dallas-Ft.Worth Regional Airport, and the PRT at West Virginia University atMorgantown" it refers to Group Rapid Transit and not PRT. All referencesto these systems in the article are irrelevant. Unfortunately the name PRT hasbeen applied to many systems over the years that are not PRT. The fact is thatgenuine PRT has never been operated in revenue service. Chicago Transit Authority’s PRT effort began as an honest exercise. From the outset PRT was defined properly and adhered to. Unfortunately Raytheonscrapped the Taxi 2000 design that won the competition and substituted its owndesign without visible rational basis. Although Raytheon by contract attemptedto design and build the right thing, true PRT, their execution was deeplyflawed. The result was a very heavy vehicle, a large and visually intrusiveguideway, propulsion and braking unsuitable for short headway operation, andconsequent cost estimates that subsequently killed the program. This was indeeda disappointing outcome for an initially promising effort. The lesson is simpleand timeless — a thing can be done well or poorly. When discussing design aspects of PRT the article reveals a serious lack ofresearch. The first criticism is the visual impact of elevated guideways. Thisis a subject that can be debated theoretically but in fact the public’sreaction and acceptance cannot be known until true PRT is operating somewhere. A proper judgment can only be made in the context of PRT’s utility and inrelation to the alternatives. In a vacuum the public would never accept massivefreeways through cities, acres of asphalt parking, congested streets, enormousenergy usage, emissions, accidents, and very high private and public costs. These attributes of our most popular urban mode are accepted only because thepublic knows the utility of automobiles from daily personal experience. Thepublic would not accept noisy 40-foot transit buses without some idea of theirlimited utility. Only after PRT is operating somewhere can informed judgmentsbe made. And, as with any automated system, guideways can be located aboveground, at-grade, or underground as desired as long as vehicles have exclusiveuse. If critics are convinced that PRT would never be accepted visually, why dothey fear its development? The article fears that "Snow and ice accumulation, rain, and otherconditions can affect or interrupt service" and wonders "How wouldpassengers extricate themselves from their little cars and guideways?" Thedesign of a leading PRT system, Skyweb Express, has addressed these issuesextensively. The proof of the design’s weather tolerance will bedemonstrated at the PCF. Well-meaning regulators may require walkways alongsidethe PRT guideways until their need is refuted in actual service. Extensiveanalysis of dealing safely with failed vehicles has shown that walkways are notan optimal solution. The critics show no evidence of knowledge of thisanalysis. If they are convinced that this is a fatal flaw of PRT, why do theyfear it so? The fear of "system droppings" also reflects a lack of understanding of theSkyweb Express design. The vehicle chassis is a very simple machine with verylittle that would produce "droppings" and the guideway is mostlyenclosed on the underside. In criticizing PRT station size the team obviously is unfamiliar with theSkyweb Express design. An elevator is included and the station is ADAcompliant. The PRT system offers a whole new world of convenient mobility todisabled persons. Why would PRT critics not even allow the demonstration ofthis capability? What do they fear? In speculating about a PRT station not being able to accommodate "themassing of large numbers of passengers" the critics fail to grasp thefundamental nature of PRT. Passengers are not massed awaiting the scheduledarrival of a massive conventional transit vehicle. Passengers depart withlittle or no wait. They flow through the station as opposed to gathering inbunches to meet the needs of old technology. If the system is so popular thatstation capacity becomes an issue, then more stations can be added withoutimpacting service to others on the system. Indeed, as with all transit, havingtoo many customers is a happy problem, much more easily dealt with by PRT thanby conventional modes. The whole section titled "Concept from 1960s" adds nothinguseful to the debate. Before the Wright Brothers first successful flight therehad been decades of failed attempts and legions of skeptics saying it wouldnever be done. So? The debate should focus on the viability of aquality design such as Skyweb Express. This kind of debate can only occur whencritics take the time to learn about and understand the design. I have yet tomeet a PRT critic who has actually read the design documents. No critic ofSkyweb Express has to my knowledge challenged the physics, math, or engineeringof the design. The section concerning line capacity reveals a fundamental misunderstandingof PRT. It is a network system, not a line haul system. Unlike in conventionalrail transit, passengers are not massed at a few stations to be transportedalong a few lines. Travel on a PRT network responds to the reality of widelydispersed passengers starting and ending their trips at locations all over ametro area. There is no artificial need for very high line capacity as is thecase with conventional transit. Nevertheless, the Skyweb Express system isdesigned for safe, very short headways and high line capacity. The critics areapparently unaware of the extensive analysis of safe short headway design asproduced by Skyweb Express. Initial deployments will not need the line capacitydesigned into the system. Regulators who impose requirements such as brick wallstopping criteria will have the opportunity to learn about safe short headwayoperation during early applications of true PRT. As is also the case withemergency evacuation walkways, once regulators understand PRT they will be ableto devise regulations appropriate for it rather than mandate preconceivedregulations based on old technology. The section on PRT station congestion really loses touch with the reality ofa good PRT design. System simulation by Skyweb Express is not an animation. Itoperates with the control equations that would drive the actual systemcomponents and do drive the prototype vehicle. It is incumbent on an honestcritic to learn about the control system design and to understand the inputs tothe simulation. Only then is a critic ready to challenge the PRT stationsimulation. The speculations in the article are nonsense. And again, what dothe critics fear? If PRT station capacity is truly a fatal flaw as they contendwhy not let PRT have a chance to fail? In criticizing PRT cost estimates the article merely states the obvious. Athing can be done well or poorly. If the critics read the Skyweb Expressdocumentation they will learn that every design decision has been rigorouslymade to minimize the life cycle cost per passenger trip. A vast number of designoptions could be, and on other systems have been, chosen so as to increasecapital and operating costs. Would the critics deny advocates the chance toprove the estimates? If so, why? Urban citizens all over the world havebeen concerned about congestion, sprawl, air quality, and energy consumption fordecades. During these decades the only alternatives seriously considered havebeen more road capacity and conventional transit modes. It should come as nosurprise that today we are concerned about congestion, sprawl, air quality, andenergy consumption. And if our planning studies continue to offer only the samemix of options, decades from now we will still be concerned about congestion,sprawl, air quality, and energy consumption. "Proven technology" suchas LRT will not get us where we want and need to go. Transit is almost uniquein its attitude against innovation. Automation is bringing substantial benefitsto most other industries. Automation could bring enormous benefits to urbantransportation. The environmental benefits of widespread deployment of PRT woulddwarf those of almost any other technology development. Why is the transitindustry so resistant to giving this mode a chance? In pondering the massive and sustained opposition to PRT, one can pondermotives. Is it fear, fear that PRT might succeed and compete successfully withconventional modes? Is it greed, an unwillingness to allow even a table scrapto go to those willing to innovate? Is it laziness or lack of time that keepscritics from learning the facts about PRT? It is difficult for me to attributebad motives to transportation professionals. Many of them are friends and peerswhom I hold in very high regard. It is a profession characterized by hard work,integrity, and a high sense of public service. However, for reasons that I donot understand, they seem to wear blinders when it comes to helping createadvanced tools for their box of solutions. My suggestion to critics is to adopt an attitude of cooperation. LRT and PRTcan be mutually supportive. In my town we are building a massive Interstatehighway expansion project that includes LRT. In several cases the LRT stationwill be at an interchange surrounded by vast office complexes on both sides. IfI offered a ride to someone in one of these office buildings and only took themas far as the interchange they would be rightfully disappointed. TransferringLRT passengers to buses would restrict ridership as the buses contended withcongestion and riders had to make stops not of their choosing. Would it beunreasonable for planners to simply study the opportunity for PRT to provide thecollection/distribution function? LRT would support PRT ridership and PRT wouldsupport LRT ridership. It seems like a win-win opportunity to me. This rebuttal will not change the minds of the critics. Hopefully, however,readers with open minds will learn about true PRT from the numerous sourcesavailable and will support giving it a chance to compete with as well ascompliment conventional transit. Fear not. The truth will not hurtyou. |