Editing Personal rapid transit (section)

===Vehicle design===
Vehicle weight influences the size and cost of a system's guideways, which are in turn a major part of the capital cost of the system. Larger vehicles are more expensive to produce, require larger and more expensive guideways, and use more energy to start and stop. If vehicles are too large, point-to-point routing also becomes more expensive. Against this, smaller vehicles have more surface area per passenger (thus have higher total air resistance which dominates the energy cost of keeping vehicles moving at speed), and larger motors are generally more efficient than smaller ones.

The number of riders who will share a vehicle is a key unknown. In the U.S., the average car carries 1.16 persons,<ref>Skytran Web Site: See "common sense"</ref> and most industrialized countries commonly average below two people; not having to share a vehicle with strangers is a key advantage of [[private transport]]. Based on these figures, some have suggested that two passengers per vehicle (such as with [[skyTran]], EcoPRT and Glydways), or even a single passenger per vehicle is optimum. Other designs use a car for a model, and choose larger vehicles, making it possible to accommodate families with small children, riders with bicycles, disabled passengers with wheelchairs, or a [[pallet]] or two of freight.

====Propulsion====
All current designs (except for the human-powered [[Shweeb]]) are powered by [[electricity]]. In order to reduce vehicle weight, power is generally transmitted via lineside conductors although two of the operating systems use on-board batteries. According to the designer of Skyweb/Taxi2000, [[J. Edward Anderson]], the lightest system uses [[linear induction motor]] (LIM) on the vehicle for both propulsion and braking, which also makes manoeuvres consistent regardless of the weather, especially rain or snow. LIMs are used in a small number of rapid transit applications, but most designs use [[rotary motor]]s. Most such systems retain a small on-board battery to reach the next stop after a power failure.  CabinTaxi uses a LIM and was able to demonstrate 0.5 second headways on its test track.  The Vectus prototype system used continuous track mounted LIMs with the reaction plate on the vehicle, eliminating the active propulsion system (and power required) on the vehicle.

[[ULTra]] and 2getthere use on-board batteries, recharged at stations. This increases the safety, and reduces the complexity, cost and maintenance of the guideway. As a result, the ULTRa guideway resembles a sidewalk with curbs and is inexpensive to construct.  ULTRa and 2getthere vehicles resembles small automated electric cars, and use similar components.   (The ULTRa POD chassis and cabin have been used as the basis of a shared autonomous vehicle for running in mixed traffic.<ref>{{cite news |title=Westfield Technology Group autonomous POD confirmed for Fleet Live 2019 |url=https://www.fleetnews.co.uk/news/fleet-industry-news/2019/08/01/westfield-technology-group-autonomous-pod-confirmed-for-fleet-live-2019 |access-date=28 June 2021 |date=1 August 2019 |archive-date=28 June 2021 |archive-url=https://web.archive.org/web/20210628030728/https://www.fleetnews.co.uk/news/fleet-industry-news/2019/08/01/westfield-technology-group-autonomous-pod-confirmed-for-fleet-live-2019 |url-status=dead }}</ref>)

====Switching====
Almost all designs avoid [[Railroad switch|track switching]], instead advocating vehicle-mounted switches (which engage with special guiderails at the junctions) or conventional steering. Advocates say that vehicle-switching permits faster routing so vehicles can run closer together which increases capacity.  It also simplifies the guideway, makes junctions less visually obtrusive and reduces the impact of malfunctions, because a failed switch on one vehicle is less likely to affect other vehicles.

Track switching greatly increases headway distance. A vehicle must wait for the previous vehicle to clear the junction, for the track to switch and for the switch to be verified.  Communication between the vehicle and wayside controllers adds both delays and more points of failure.  If the track switching is faulty, vehicles must be able to stop before reaching the switch, and all vehicles approaching the failed junction would be affected.

Mechanical vehicle switching minimizes inter-vehicle spacing or headway distance, but it also increases the minimum distances between consecutive junctions. A mechanically switching vehicle, maneuvering between two adjacent junctions with different switch settings, cannot proceed from one junction to the next. The vehicle must adopt a new switch position, and then wait for the in-vehicle switch's locking mechanism to be verified. If the vehicle switching is faulty, that vehicle must be able to stop before reaching the next switch, and all vehicles approaching the failed vehicle would be affected.

Conventional steering allows a simpler 'track' consisting only of a road surface with some form of reference for the vehicle's steering sensors. Switching would be accomplished by the vehicle following the appropriate reference line – maintaining a set distance from the left roadway edge would cause the vehicle to diverge left at a junction, for example.