Personal Rapid Transit Capacity Compared to Rail Transit |
| Concern: | PRT can never have the capacity to carry as many people as traditional rail transit because the vehicles are too small. |
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| Reply: | Not true! The capacity of a transit line is dependent upon two factors: the capacity of the vehicle and headways. While rail transit has chosen to focus on using large vehicles, PRT focuses on reducing the headways and keeping the benefits of small vehicles. The minimum headways proposed for a PRT system are one-half second. So the maximum number of vehicles passing a point per hour is:
The above is vehicles per hour. The number of passengers per hour is vehicles * average load factor. Assuming the system has the same loading rates as automobiles (1.2 passengers) gives: This is the maximum theoretical throughput at one-half second headways. Since the maximum values are rarely attained in any system, we use 80% of this, or 6912 passengers/hour, for comparisons. 6912 passengers per hour is the equivalent of three-car sets of 200-passenger light rail cars at just over five minute headways. When you consider that 200-passenger cars are some of the largest light rail vehicles AND that few light rail systems ever operate at less than 7 minute headways (10-minutes is more typical), you can see that PRT can indeed carry as many people as light rail. |
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