Editing Personal rapid transit (section)

====Capacity====
PRT is usually proposed as an alternative to rail systems, so comparisons tend to be with rail. PRT vehicles seat fewer passengers than trains and buses, and must offset this by combining higher average speeds, diverse routes, and shorter headways. Proponents assert that equivalent or higher overall capacity can be achieved by these means.

=====Single line capacity=====
With two-second headways and four-person vehicles, a single PRT line can achieve theoretical maximum capacity of 7,200 passengers per hour. However, most estimates assume that vehicles will not generally be filled to capacity, due to the point-to-point nature of PRT. At a more typical average vehicle occupancy of 1.5 persons per vehicle, the maximum capacity is 2,700 passengers per hour. Some researchers have suggested that rush hour capacity can be improved if operating policies support ridesharing.<ref>{{cite web
 | url = http://pubsindex.trb.org/document/view/default.asp?lbid=803547
 | title = Doubling Personal Rapid Transit Capacity with Ridesharing
 | last = Johnson | first = Robert E.
 | year = 2005  | access-date = August 30, 2017
 | work = Transportation Research Record: Journal of the Transportation Research Board, No. 1930
}}</ref>

Capacity is inversely proportional to headway. Therefore, moving from two-second headways to one-second headways would double PRT capacity. Half-second headways would quadruple capacity. Theoretical minimum PRT headways would be based on the mechanical time to engage brakes, and these are much less than a half second. Researchers suggest that high capacity PRT (HCPRT) designs could operate safely at half-second headways, which has already been achieved in practice on the Cabintaxi test track in the late 1970s.<ref>{{cite web
 | url = http://faculty.washington.edu/jbs/itrans/big/soa2.pdf
 | title = Emerging Personal Rapid Transit Technologies
 | last = Buchanan | first = M. |author2=J.E Anderson |author3=G. Tegnér |author4=L. Fabian 
 | author5=J. Schweizer
 | year = 2005  | access-date = August 30, 2017
 | work = Proceedings of the AATS conference, Bologna, Italy, 7–8 November 2005
 }}</ref> Using the above figures, capacities above 10,000 passengers per hour seem in reach.

In simulations of rush hour or high-traffic events, about one-third of vehicles on the guideway need to travel empty to resupply stations with vehicles in order to minimize response time. This is analogous to trains and buses travelling nearly empty on the return trip to pick up more rush hour passengers.

[[Grade separated]] light rail systems can move 15,000 passengers per hour on a fixed route, but these are usually fully grade separated systems. Street level systems typically move up to 7,500 passengers per hour. Heavy rail subways can move 50,000 passengers per hour per direction.  As with PRT, these estimates depend on having enough trains.

Neither light nor heavy rail scales operated efficiently in off-peak when capacity utilization is low but a schedule must be maintained.  In a PRT system when demand is low, surplus vehicles will be configured to stop at empty stations at strategically placed points around the network. This enables an empty vehicle to quickly be despatched to wherever it is required, with minimal waiting time for the passenger.  PRT systems will have to re-circulate empty vehicles if there is an imbalance in demand along a route, as is common in peak periods.

=====Networked PRT capacity=====
The above discussion compares line or [[corridor capacity]] and may therefore not be relevant for a networked PRT system, where several parallel lines (or parallel components of a grid) carry traffic. In addition, Muller estimated<ref>{{Cite web |url=http://www.leighfisher.com/trb/657-2-05-0599.pdf |title=Muller et al. TRB |access-date=2006-09-25 |archive-url=https://web.archive.org/web/20060831081723/http://www.leighfisher.com/trb/657-2-05-0599.pdf |archive-date=2006-08-31 |url-status=dead }}</ref> that while PRT may need more than one guideway to match the capacity of a conventional system, the capital cost of the multiple guideways may still be less than that of the single guideway conventional system. Thus comparisons of line capacity should also consider the cost per line.

PRT systems should require much less horizontal space than existing metro systems, with individual cars being typically around 50% as wide for side-by-side seating configurations, and less than 33% as wide for single-file configurations. This is an important factor in densely populated, high-traffic areas.