Capacity in a RUF system
Palle R Jensen, RUF International
A highway lane is normally considered to have a capacity of 2000 cars per hour. Normally, nobody mentions that this capacity can only be obtained at a lower speed than the top speed allowed on the road. The maximum flow will probably exist at 50 mph or less.
If a system can come up with the same capacity but at top speed, it must be considered to be a better system.
A train system can show very large capacity numbers in theory. If nobody wants to use the train, the availability of this capacity makes no sense. Numbers are not enough.
Which aspects should be considered when talking about capacity in transport systems?
Peak capacity is interesting. Trains have high peak capacity. A system as RUF, with smaller but more frequent vehicles, has also a relatively high peak capacity.
"Granularity" is interesting. Trains are really bad in this respect. They move their passengers in big lumps. The passengers have to adjust their rhythm to the fixed timetable of the train.
Redundancy is important. A line bound system with on-line stations is very vulnerable and the timetable is very hard to keep. Disturbances will easily spread to the rest of the system (e.g. connecting busses). A system with off-line stations is much more redundant. If the platforms are parallel platforms as in the station design for maxi-rufs, the redundancy is even higher. A problem with one vehicle at a station will not affect the others.
In a network there are junctions. They may be the limiting factor, so that a high line-capacity may not be relevant. If the junction cannot handle the flow, the available line-capacity cannot be used. In a RUF system, the junctions are organized in such a way that the line flow is split into several independent directions in order to maximize the flow through the network. The incoming guideway will be split into 3 guideways. One for the vehicles continuing straight ahead. One for the ones turning right and one for the rest. This way the line can have high capacity and the junction can handle all relevant changes of direction. A simulator is under construction. Its goal is to prove that this design if possible and to come up with realistic capacity measures for the system.
Space requirements are important. High capacity can, in theory, be obtained if the speed is very high in a system. Sub-second headways may be obtainable, but the laws of physics cannot be ignored. Humans will not use a system if it is uncomfortable. There are limits to jerk (change of acceleration) and acceleration. When you take these into account, you will see that at high speed you will need a lot of expensive space to make the turns and to decelerate the vehicles before they can get on and off. In the RUF system, all vehicles slow down to 20 mph during switching. This means that the radius of curvature can be as little as 26 m. It also means that when a ruf leaves the guideway, no lengthy deceleration ramp is needed. In an existing city it will often be impossible to find room for guideways that have to have a large minimum radius of curvature.
Area coverage is also important. It is of no use to be able to move a lot of people between two stations if the passengers live far away from the stations. A PRT system may have more stations than a train system, but the ultimate solution is a Dual mode system like RUF. It has a high capacity also in the sense that it appeals to people wherever they live. A fuel cell ruf can be used by those living out in the rural areas, but working in the big city.
Flexibility means high capacity in the sense that the flexible ruf can be used to solve all kinds of transport problems. It can move not only people, but also goods. It can be used as a shelter when you enjoy a view in the mountains. It can be used to power electronic equipment out in the field. It is a private room when you need to have privacy, no matter where you may be.
The success of the car is no surprise. It is extremely well-adapted to modern life styles (and a creator of the same). A Dual Mode system as RUF has the capacity to make the "car" more efficient and environmentally friendly. It also has the appeal which makes it realistic to change from car to ruf. This transition can carried out gradually via an attractive Dual Mode Public Transport system.
Last modified: March 04, 2001