I don't have to attend every argument I'm invited to. (Hollywood moviemaker Samuel Goldwyn)

omehow it is felt by most people that supported transport vehicles are safer than suspended vehicles. It feels "better" to know that one´s weight is supported form below. This has no bearing in actual life; one mode of transportation is just as safe as the other, it´s just a question of proper engineering.

General Drawbacks with having the cabin underneath the beam Advantages with having the cabin underneath the beam.

1. General

People who are afraid of travelling in suspended vehicles should be equally apprehensive of riding a skilift or stepping into an elevator. Yet, we want reliable support under our feet, it´s an ingrained feeling that is sometimes hard to reason with. This reasoning process might be aided a lot by taking in the strong arguments for suspended travel that we present on this webpage. All we have done , in a manner of speaking, with the suspended cars, is that we have moved the bogie-cars from underneath the cabin and put them on the roof.

Figure 1:2

Our cities are not as liveable as they could be, by utilizing the technology that is at our disposal. In the ideal city, the vehicle traffic has been moved away from the ground and left this ground to pedestrians and bikers. At the same time, the cities have to be easily accessible for everyone, most of all to travelers and to those who have freight to transport or send. Figure 1:3: A supported automatic train in Osaka, Japan.

Also indoors, it would be advantageous if one could let the floor be free for human activities of other kinds than transportation of goods or people. It would there seem like a natural thing to do to attach the beams to the ceilings. Suitable places for this would be industrial plants, warehouses, shopping malls and glassed-in streets. As a consequence, the beam vehicles should preferably go underneath the beams. Accessibilty both indoors and outdoors would be facilitated with a simple elevator in the vehicles, enabling passenger cabins, flatcars and containers to be lowered to the ground. This way, one avoids unnecessary long walks to stations and vertical transportation of baby carriages, wheelchairs and luggage. One would not have to build expensive stations 4-5 meters up in the air, with escalators.

Trucks could leave and pick up freight on most places along the line, not having to rely on depots. They could load/unload directly to/from the beamcars, without the freight having to touch the ground. Outdoors, the beams could be fastened to supporting poles or suspended from wires. In the latter case, it would definitely be advantageous to have the cars travelling underneath the beams. With this kind of suspension bridges, long spans could be constructed at low cost, compared to regular bridges.

In the future, proportionately more of the urban beam traffic in Western countries will likely go indoors (for instance in newly-built suburbs designed for suspended beam traffic). The berths could be placed on a suitable floor near the elevator in a high-rise building. This possibility is valuable in order to create short walking distances to parking areas for motor vehicles, and avoid unpalatable weather and climate conditions. Figure 1:4 shows how separate supported and suspended systems could be made to share the same carriages, by means of coordinated system interfaces. In this example, the beams of the two systems overlap for a length of 30 meters or thereabouts. If a carriage is to be moved from the supported to the suspended system, the following would take place: The carriage is stopped on the lower beam A propulsio car with a lift is moved into position above the carriage The lift is lowered, and locks onto the carriage The carriage is disengaged from the bogie The carriage is lifted up under the upper beam. And, of course, the reverse would take place when the carriage is to be returnded to the supported system.

Figure 1:4

2. Drawbacks with having the cabin underneath the beam

Hanging the beamcars underneath the beam brings a lot of advantages, most of which are listed further down on this page. Figure 2:1 There are also drawbacks, and right now we can think of 4 such objections to hanging cabins: Quite a few people imagine that they would feel more anxious riding in a hanging cabin than in a supported cabin. But it is a fact of life that people quickly adjust to new conditions. The "schwebebahn" in Wuppertal has been in traffic since 1901(!) and never had problems with riderships. 2 accidents have been reported during these 100 years, one involving a circus elephant(!) and the other in connection with maintenance work on the beams. Hanging carriages mean higher poles, resulting in a higher sideways strain on the pole's foot. This would only be a problem for poles carrying one beam, since 2 beams tend to balance each other out. A higher pole would be costlier, but the cost of the poles contribute less than 10 % to the total cost of constructing the physical beam network. If you consider that: a beam segment (between two supports) is 5 times as long as the pole is high, is more complicated to manufacture and contains more hardware inside a pole can, with relatively minor attachments, be made to carry 2 or even more beams all supports are not poles; som supports could be attached to buildings, etc. you will realize that the beam segment would be about 7 - 20 times as expensive, depending on the alternatives chosen (see figure 2:1). The cables and the pole footings would each contribute about 10 % each to the cost of physical manufacturing and construction (in the simplest case, as that shown in the illustration above). Costs are thus largerly offset by the possibility of attaching the beams to other structures, mainly ceilings, a possibility that supported beam systems do not have.

The carriages need to be sturdier. If you consider figure 2:2 you will realize that, since the weight of passengers and cargo rests on the floor, the superstructure on a supported carriage only serves to protect passengers and cargo from the wheather. The suspended carriage needs sturdy beams to transfer this weight to the roof, which unavoidably makes the carriage somewhat heavier and more expensive. Figure 2:2 In a mixed environment, containing beams for both suspended and supported traffic, one could, as in figure 1:4 above, use cars that could be shifted between the two systems. This would be a way of easing the transition from one system to the other, and would provide for better flexibility in the rolling stock. One concept that includes this possibility is MAT.

Figure 2:4 Combined beams for both purposes

3. Advantages with having the cabin underneath the beam

1	Lifts on vehicles A simple elevator could be built into the vehicle, enabling the cabin or flatcar to be lowered to the ground just about anywhere. This would make it possible for the vehicle to stop wherever is convenient; it would not have to rely on specific stations. This would enable convenient exchange of passengers and freight with other vehicles on the ground (see web-page 36.).
2	No need for elevated stations Suspended, elevator-equipped beamcars would save the expense of building stations 5 meters up in the air. The intrusion of these stations on the city environment would also be avoided. These 2 factors (cost and environmental intrusion) are the main reason why the stations are few and far between in the supported automatic beam system. In both systems, there could be sideline beams in parallell to the ordinary beam with frequent switches between the two in areas where frequent stop sites are desired. On these sidelines, suspended beamcars with lifts could stop anywhere, not being confined to platforms above the ground. An alternative to lifts would be to let the beam come closer to the ground, as shown in the illustration. This is a solution that would not help in the supported systems; elevated platforms would still be needed.
3	Immunity against snow and obstructions Placing the slit on the underside of the beam makes the propulsion car and the guideway totally immune to sleet, snow, rain, falling debris and other obstructions. The supported cars have to contend with either a slit on the upper side of the beam (A) for the connection of propulsion cars and cabins or, if the supported system uses propulsion in the cabins/flatcars themselves, a rail of some kind (B) on the top of the beam. Both alternatives are vulnerable to vagaries of the weather.
4	Natural adaptability to natural forces The cabins or flatcars in the suspended system can adapt to the natural forces such as the centrifugal force when the beamcar goes through a curve (see illustration, which is somewhat exaggerated). This makes for cheaper cars compared to the supported system, if one chooses to artificially lean the cars against the centrifugal force, as is done with the Swedish train "X2000". The alternative for supported systems would be to bank the beams, see the item below.
5	Cheaper manufacturing The beams will be cheaper to manufacture when they don't have to be banked (or super-elevated) to suit the bends (this is what is done in for instance Raytheon's PRT 2000). Since the investments in beams and poles for the network will dominate the total costs during the network's lifetime, this is an important consideration. Varying degrees of banking has to be done for different speeds and radius of curvature, which means that a larger variety of beams have to be manufactured.
6	Can keep higher speed Suspended vehicles can maintain roughly 30 % higher speed than vehicles travelling on top of the beam, in a city environment with many bends on the beams (because of the reason stated in item 4 above), without discomfort to the passengers and danger to the freight. This will considerably reduce travel time through the city.
7	No need to slow down in curves The vehicles in a suspended system can go through the curves at practically any speed dictated by the circumstances from time to time (such as temporary blockage of the traffic flow), without the passengers suffering any discomfort, since the cars would just bend to the centrifugal force. The supported systems that use artificial, computer-controlled leaning of the cars (as mentioned in item 4 above) can deal with these situations as well, but supported systems with banked curves can not. Have you ever been on a train that was brought to a stop in a heavily banked curve?
8	Easier evacuation in emergencies If the vehicle should stop on the beam because of some mishap, and cannot get started again within a reasonable time, the cabin with travelers and freight in the suspended system could easily be lowered to the ground, if elevators are used in the cars. For the supported system, more awkward methods would have to be used! (maybe ladders?)
9	Longer and cheaper bridge spans Inexpensive bridges with long spans could be built, by supporting the beams with long steel wires fastened at the top of the beams. If those beams carry supported traffic, the wires have to be fastened to crossbeams (C in the illustration) that then would have to support the traffic-carrying beams.
10	Easier indoor access Fastening the beams to the ceilings indoors in shopping malls and airport terminals, etc. will be a prominent feature with the suspended system and will result in savings on separate supports for the beams. Such practical solutions are out of the question for supported systems. Newly-constructed buildings adapted to the suspended system will have the beams inside the ceiling, as part of the structure itself. The beam could thus do double duty as support for the structure.
11	Less accident-prone In the suspended system, there is no risk of the beam car hitting people who for some reason have entered the beam. A strong reason why underground trains in at least Stockholm won't maintain traffic through the night is that people in the tunnels are getting hit by the trains.
12	Less risk of sabotage The possibility of sabotage by throwing rocks and other stuff onto the rails is largerly eliminated in the suspended system. The saboteur would have to find a way to jam the slit underneath the beam. Also, beam vehicles, parked hanging underneath the beam, about 5 meters above the ground, are more inaccessible for sabotage in the suspended system than are vehicles parked on top of the beams. Unless (of course) the beams themselves are adequately protected from illicit access, which is not that easy. Saboteurs are usually agile persons.
13	Less danger of fire Since motors and power lines in the suspended system are above the cabin or flatcar, there is considerable less risk of spreading of fire to people or freight, as compared to the supported system.
14	Reduced traffic noise In the suspended system, the beam is one vehicle height higher above the ground than in the supported system. This means reduced noise and less visual intrusion at the street level. It should be admitted, though, that the poles will be higher (thus probably a bit costlier) in the suspended system.
15	No risk of derailment Suspended cars cannot tip over or become derailed. If elevators are used, these would also effectively reduce the effects of unevenesses in the beams, thus functioning as shock absorbers.
16	Room for extra causeway The top of the beam could conceivably, in the suspended system, be used for other purposes. It could under special circumstances, such as when the beams are spanning a ravine or similar obstacle, be broadened somewhat, supplied with fences and thus become a pedestrian walkway and/or bike route. This option would function better if constructed on top of two beams in parallel; that would make it broader. It could also be used to erect solar panels. In tropical countries, these two functions could be combined insofar as the solar panel could be erected above the walkway, thus providing shadow for pedestrians or bikers.