Personal rapid transit guideway routing starts with the locating of stations. The process is iterative with the station locations being tweaked as the guideway routing is developed. Considerations include space availability, circuitousness, visual intrusion and bottlenecks.
There are two basic ways of laying out personal rapid transit guideways. The first consists of a series of loops which result in a series of merges and diverges. A limitation is that a merge always precedes a diverge, and so two streams of traffic combine before separating. The result is that the short sections of guideway, with combined traffic, become bottlenecks, and capacity is quite significantly constrained. This concept also results in more circuitousness (follow the green routes from top to bottom or right to left).
The second layout for personal rapid transit guideways incorporates overpasses. In this concept, a diverge precedes a merge at each intersection and the overall capacity is much higher. Another advantage is that trips are much more direct with less winding. Since most personal rapid transit systems have elevated guideways, the additional cost of overpasses is minimal and can be offset by the time savings and reduced number of vehicles needed for the more direct routing that results
A third configuration is possible, wherein the circuitousness of the merge/diverge layout is minimized, and the ability to later convert some intersections to overpasses is retained. It should be noted that the above options do not include dual direction guideways. While these can be desirable in specific instances, they are to be avoided in general for the following reasons:
When laying out a personal rapid transit guideway system over a large area, it is usually best to start out with a theoretical rectangular grid system, with guideways spaced at the desired station spacing (usually about one half mile). The guideway directions should alternate and the grid system should approximately match the defining features, such as the underlying road system. Once this personal rapid transit grid system is in place, it can be adjusted to match constraints, such as specific station locations, road right-of-ways and terrain, as required. The resulting layout may no longer resemble a grid at all, but the simple logic of the grid system will be retained.
Even a small pilot system for personal rapid transit should be approached in this way, with the ultimate guideway network first being developed. This ensures a rational layout that will minimize out-of-the-way travel. The pilot system guideways can then be selected, knowing that future expansions will be possible, without the need for major adjustments. The preferred route analysis will require the participation of stakeholders of all types. Joint Development and TOD opportunities should be considered.
Storage of personal rapid transit vehicles in off-peak periods and overnight must be considered when selecting preferred routes. While PRT vehicles will be stored in the maintenance/storage facility, supplemental storage may be required to facilitate rapid deployment. Storage in stations is always a possibility.