Dualmode and Personal Rapid Transit (PRT) Guideway Loading and System Planning Considerations


Walt Velona

August 16, 2000

Our road to energy independence will start when we will have erected the first column of our new Dualmode guideway system. Long before this moment arrives, you fine people must decide how far apart are the columns and how much of a load they will carry. The load will depend on what they will carry. This, then, is the subject of this letter.

I have concluded that the heaviest load on both the Intercity and Urban Dualmode guideways systems will be less than the weight of a fully loaded eighteen wheeler truck and perhaps no more than the weight of a car or small truck on a pallet. The Dualmode guideways will be designed to provide non stop entry to suspended Dualmode vehicles; to carry vehicles supported on pallets; to provide PRT service, and to carry such other traffic as will serve the special needs of various entrepreneurs. The PRT system will be designed to carry nothing heavier than the weight of a capsule with 3 or 4 people.

I believe that Kim Goltermann will have his wish to retain ICE, the internal combustion engine. The advent of the 80 miles per gallon car is a revolution that will prolong the age of petroleum. When crude oil is gone, we will have synfuel from coal or natural gas, or alcohol from the farms. At the much higher prices we will experience in the days ahead, old oil fields will be reactivated and new methods will revitalize them. We may also have hydrogen fuel cells, at least for heavy trucks. These vehicles will be used by those who cannot or should not or do not want to convert to electricity.

Guadagno (see InTransSys page) has estimated that oil will be gone within 20 years. My own guess is that he is both pessimistic and optimistic. My judgment is its price will be so high that it will create shortages. This shortage in turn, will prolong its availability long after 20 years. Producers should reduce the flow of oil and increase the price to maintain current income levels into the next century. (I realize that I am ignoring the shape of the demand curve, but the following statement makes my point.) Thus if production is cut down to 20% of current flow, the price of gas would have to be five times higher or $8 a gallon. At that price all sorts of fuels will come to market. The total energy supply will not be plentiful, and the fuels will be expensive, but for the foreseeable future into the next century, perhaps there will be enough for those who can afford the high price. But Guadagno is right. We will have shortages, and I believe, long before 20 years.

This availability not only prolongs the life of the ICE, but also guides us in deciding the design of our guideways that use electricity. Electricity must be manufactured. Fortunately, we have enough coal and natural gas to take care of our needs in this century. I myself am in favor of nuclear power, but this is not an issue we need to address at this time. We should at once reinvigorate our research in nuclear methods of electricity production and perhaps by the time or even before all our fossil fuels are gone, new methods of production will continue to give us the electricity we will need for this and the next millennium.

In what follows, I assign roles to the railroads, to trucks, to ICE vehicles, to electric automobiles and to electric guideways. Each has a role to play based on its attributes and on the available supply of energy. But, before I begin to assign these roles let me make another point or two.

Given that we do not now have either electric highways or electric cars, we must consider ourselves fortunate that government has had the foresight to sponsor the development of the 80 miles per gallon automobile. I suppose we should also give government credit for sponsoring research to lower the cost of synthetic fuel from coal. However, although this may benefit the public by stimulating an increase in the supply of fuel, the cost savings are not likely to accrue to the public since the price will not be a function of production cost but rather of demand. By the time this fuel enters the market its price will be far above its production costs.

I have seen no indications that electric cars will ever be able to match the performance of the ICE cars and trucks in all respects. As gasoline becomes in short supply, the internal combustion engine may have to be adapted for the variety of fuels that will become available, but as I have argued above, it is doubtful that it will disappear in the foreseeable next one or two centuries. There are simply too many applications where it will be the engine of choice, even with the high cost of fuel. We need it in our tractors on the farms, we need it to travel the 3 to 4 million miles of roads that will never be served by guideways or electric cars. We need it to use in the trucks that carry the heavy loads that will not be carried by the guideways, we need it for military purposes, and of course we will need it for our airplanes.

For 30 some odd years, I have thought that our national intercity Dualmode system would consist of a 100,000 mile network. I am now convinced we will only need 50,000 miles of network. Your finding that we can build a 60 miles an hour version of Dualmode will allow us to create cities 100 miles wide. Such cities along the Interstate Highway System would create 50,000 miles of overlapping corridors 100 miles wide. As much as one half of our nation’s land area would be served. Accordingly, I now believe that our ultimate guideway network will consist of 50,000 miles of intercity Dualmode, 35,000 of urban Dualmode and 15,000 miles of PRT guideways. That will leave almost two million square miles of our land with little traffic. This should have a salutary effect on our environment.

A look at our maps confirms that our main roads follow the paths of our railroads. Our cities are the product of our railroads. The people of those cities are now traveling on beautiful highways along the paths of these pioneering railroads as they visit their wandering children who left home to find a job and a mate in a distant city. (This is a little corny, but what is wrong with a little corn?)

In my view, the Dualmode system will greatly enhance the role of the railroads. The transportation role they play is too important and the nation should never be without them. We should look upon them as a guideway specifically designed to do the work that cannot be done by the Dualmode guideways. After all, they need not be affected by the oil shortage. They can go back to coal. They can use natural gas and they can convert to electricity. They are needed to carry heavy steel girders, large concrete pipes, steel plates for tanks and factories, mine products, construction equipment and military tanks. They can also carry all sorts of freight that do not have to move quickly. They can carry the products of our farms and, most importantly, they may well become the principal mode of travel for that half of our nation that is not served by the Dualmode system. As an added bonus, they give us the security of a backup to the Dualmode system in event of a massive power failure or disaster affecting guideway operations.

The railroad is only one part of the total trip and we need to consider how freight is transported to and from the railroads at the origin and destination. This is where we will still need the internal combustion engine. Most of these will be short trips usually within an urban area. Clearly we will have to continue using trucks to carry these heavy objects. When oil becomes too scarce, perhaps the trucks will use alcohol to take its place, or perhaps hydrogen, or they might use electricity. I remember the electric trucks running on solid tires along the streets of New York when I was a kid. We may conclude that none of the dualmode systems will be designed to carry railroad freight. It is also possible that the railroads will be expanded with sidings to strategic urban locations that will serve to shorten the truck portions of the freight trips.

Before discussing the role of dual mode, I should point out that a common sense design criterion states that if the guideway is made stronger to accommodate a certain heavier weight, the added cost of achieving that extra strength will be borne solely by the object that has that weight. What we must not forget is that in making that decision, we are committing ourselves to thousands of guideway miles designed to carry additional weight to be paid by a very small percentage of the national traffic. This principle is enforced by carefully scaling guideway fees to not only pay the cost of electricity but also a fair share of the capital costs.

The prime example for testing this design criterion is the fully loaded eighteen-wheelers. Based on our policy, shippers would have to pay a premium for shipping the added weight of the truck. Many of them would also have to pay the driver if he went on the trip. Clearly, this would place a cost burden that the shipper can avoid by simply converting all shipments to containers. In anticipation of this result, we should not expect that the additional costs of building a heavier guideway will ever be recovered. Our only choice is not to build the heavier guideway in the first place. We can conclude that the guideway should accept freight only when carried in a container.

The next question is whether the load carried by eighteen-wheelers should be divided into smaller containers. In other words, should the guideway carry anything heavier than cars and small trucks on a pallet. The answer is yes, but only if the final design is heavier because of some such consideration as tradeoffs between maglev deflection requirements, column spacings, and the size beam required to carry its own weight plus no more than the weight of a car or small truck on a pallet.

I see no problem in accepting reduced container weights if it is found that this will result in significant cost savings. This will force the shipper to divide his load into smaller batches and to buy more containers. On the other hand, if we do not exercise the option to use the lower weight, the shipper will have to pay higher fares to compensate for the heavier design needed to carry his load. You might say that the shipper is caught between a rock and a hard place. He will have to pay extra to ship a large container, or else he will have to pay extra to ship in small containers. This makes him indifferent to the issue. We who are the designers are not indifferent. We want to reduce the capital cost to a bare minimum and, if justified, we will design for the small containers.

I see no reason to change the loading criteria of the urban version of the dualmode system. Admittedly, there is a considerable volume of heavy truck movements within urban areas. Concrete trucks are an example. If we build a guideway to handle this kind of a load, these trucks would have to pay the added cost of the guideway. This will never happen. These vehicles will find it more economical to continue to rely on the ICE despite the high cost of whatever fuel might be in vogue. And as I stated above, in some cases railroad sidings will be constructed to shorten the local trips by trucks.

Finally, let us consider the needs of the transit neighborhoods in urban areas.

But first, I must describe how I analyze transportation within a city. It goes something like this:

I divide the entire city into neighborhoods. Each neighborhood has a very definite and uniform requirement. No resident in the neighborhood lives more than 7 minutes from a grocery store. What I am really saying is that no one should spend more than 7 minutes door-to-door time to get a quart of milk, or a loaf of bread, or a six-pack of beer. If there are residents more than 7 minutes from a grocery store, after a while they will move away if a grocery does not locate 7 minutes from his residence. I don’t know if 7 is the right number but someone someday long after I’m gone, will come up with the best number to use. The location of the grocery store is also the logical location for the transit or guideway stop. You will want to stop for a bag of groceries before continuing on your trip home.

I also assume every city is an hour in diameter, whether the city is full or empty. Thus every city is actually three cities in one. I assume the Central Business District is common to all three. Because of their different average velocity, the Walking City is the smallest, the Transit City is superimposed on the Walking City and the Automobile City is superimposed on both of the other two cities. I now clearly define Suburbia as that part of the automobile City that extends beyond the Transit City. When we add the faster Dualmode, it will create a larger Dualmode City. The part that extends beyond Suburbia I have dubbed Maglurbia.

In America, we have only two travel options when traveling within a neighborhood. We walk or we use an automobile. Someday we may create bicycle, moped, wheelchair or go-cart neighborhoods. What is important is that each such neighborhood differs in size depending on the average velocity of the mode. In our Transit City portion of our cities, transit riders walk and they form the smallest neighborhood. There are 16 walking neighborhoods within each automobile neighborhood. Because population densities are lower and average velocities are higher, suburban automobile neighborhoods are larger than Transit City automobile neighborhoods. And there are no walking neighborhoods within suburban automobile neighborhoods.

I assume our intent is to connect all the automobile neighborhoods with our Urban Dualmode guideways. I will now suggest that we connect all our walking neighborhoods with a PRT guideway. We will also provide PRT service on the Urban Dualmode guideway.

We now have all the guidance we need to locate our stations. Since these stations are to be located at the center of each neighborhood, all that remains to do is to convert the 7 minute travel time to distances. We find that the Transit City PRT guideway stations will be 2/3 of a mile apart. Within the Transit City, the automobile stations are 2 and 2/3 miles apart. Within Suburbia, the stations are 4 miles apart. We will note that there are 16 PRT stations within each Transit City automobile area. We hope this will serve to convert automobile users to PRT on all trips to congested areas of the city. Since there are no walking neighborhoods in Suburbia, we will build parking areas at each stop that will encourage the use of PRT to congested destinations. Surely this is a plan that should eliminate our nation’s serious and mounting congestion problems.

I have one more suggestion for you to kick around. I propose one way travel on all Dualmode and PRT guideways. In Transit Cities, parallel PRT guideways will be constructed 1/3 of a mile apart, and the Dualmode guideways will also be 1 and 1/3 of a mile apart. In Suburbia, the Dualmode highways will be 2 miles apart. What I am suggesting is that alternate parallel guideways travel in opposite direction. Given the high speeds, crossover loops which allow the vehicle to reach its station can be as much as 3 or 4 miles apart without causing a significant loss of travel time. Electricity costs will be a little higher, but we reduce construction costs by almost one half. This is too significant to ignore. (This assumes of course that the technology exists to provide the smooth melding of two streams of traffic moving more or less at the same speed.)

Most of the users of the Transit City PRT guideways are people without a car. Some of them may have a bike or a moped, or a wheelchair which they may wish to carry to their destination for use within the destination neighborhood. This suggests that a very light guideway system carrying small capsules will be adequate for the PRT guideway system.


In re-reading this paper I find that I have accidentally created a new transportation mode. I will call it Dual-PRT. You will notice that a traveler from a suburban neighborhood now has PRT access to every destination within the Transit City. He can park his car at the Dualmode Station (Its new name is now the Dual-PRT Station) in Suburbia, take the PRT to any destination in the Transit City and he will have no more than a 7 minute walk to his
destination (The walk will do him good.)  The only time anyone in the city needs to use the Dualmode is when the destination is to a suburban neighborhood. Does this solve the CBD congestion problem?

There is another thought that I would like to pass along. It appears that we will always need the internal combustion engine. The sooner we build the entire network the more oil we conserve for the future. Since we cannot do without the ICE in the future, we should not squander its fuel now. Not when we have an alternative. This may be the most powerful argument we can offer to not delay in getting started with Dualmode and PRT.


Last modified: August 17, 2000