A typical PRT Trip

A PRT trip is like riding a driverless cab from your closest bus stop to the bus stop closest to your destination.

When you arrive at the departure stop a vehicle is already waiting for you. You enter the vehicle alone or with your selected company. As soon as you have entered the vehicle and selected your destination the vehicle starts.

The trip leads you the fastest route to the destination, skipping all intermediate stops. As the vehicle does not share lanes with regular traffic you don’t have to stop at traffic lights and other road obstacles. Instead you ride soundlessly and in an even pace above the city traffic until you reach the destination and leave the vehicle.

When you have left the vehicle it is available for another party. If there is already a sufficient number of empty vehicles at the stop the first vehicle in line leaves to fill in a vacancy at another stop in the vicinity which is short of empty vehicles. In this way the risk of having to wait at the departure station is minimized.

Components of a PRT system

A PRT system consists of a guideway system, vehicles, stops and a central control system.

The guideway system typically consists of beams which are suspended from posts at regular intervals. The beams are high enough above street level to allow car traffic to flow under them. The beams have specific running surfaces for the wheels of the vehicles. The guideway system also has switches where vehicles can select the left or right beam. There are almost as many ideas on how to implement the guideway and switches as there are proposed PRT systems. There are supported systems where the vehicels run on top of the beam, cantilevered systems where the vehicles run on one side of the beam and suspended systems where the vehicles run below the beam. Each have advantages and drawbacks. At Beamways we have come to the conclusion that a suspended system provides the best trade off and have designed our system accordingly.

PRT vehicles are small, 2-5 seats is typical. Propulsion is always electric but the power source can be on board batteries or a power rail inside the guideway beam. Some systems dispel of the regular electric motors and use linear motors instead. Beamways uses regular motors and a power rail, which offers the lowest energy consumption.

PRT stations typically have a side track connected to the main track with a switch in each end. Vehicles leave the main track at the first switch, brake and stop to allow passengers to leave and enter in the middle and then accelerate and reenter the main line at the second switch. For systems with car-like vehicles other options are available like for instance curb parking. Most systems intend to have all stations at the same level as the normal guideway but some, notably Mister and Beamways, allow such steep slopes that stations at ground are feasible.

The central control system has many tasks, but maybe the most important one is to distribute traffic information to all vehicles so that congestion can be avoided. This is done by redirecting vehicles on a slightly longer route when necessary. As the central system can keep track of where vehicles are headed ahead of time congestion can be avoided before it actually sets in. Some systems allow central control to reduce the speed on the most heavily used lines in extreme traffic , thereby reducing the headway (time between vehicles). This is like a controlled queue where maximum throughput of the beam is preferred over maximum speed of the individual vehicles.

Other tasks of the central control system are to make sure that all vehicles are cleaned and maintained regularly, to allow passengers to talk to a human operator if they encounter problems and to handle the billing of the rides.

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