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here are five reasons an in-vehicle switch is superior to a moving-track switch. Reliability. The simplicity of the in-vehicle switch makes it inherently more reliable than the in-track switch, and an in-vehicle switch can easily be made bi-stable by means of a spring. The worst that can happen with a well-designed in-vehicle switch is that one small vehicle will be misdirected, whereas if an in-track switch fails, it ties up a whole line of traffic, thus delaying many people. Also, the in-track switch requires an electric or hydraulic actuator mounted in the guideway, which upon failure shuts down the line. The result is that the required reliability cannot realistically be attained if the switch is in the track, but is easily attained if the switch is in the vehicle. Capacity. Because of the time required 1) to move an in-track switch, 2) to verify that it is locked in position, and 3) to be able to stop before the vehicle reaches the switch if verification is not obtained, the minimum time headway will be too long to be of use in a PRT system. An in-vehicle switch completely removes this barrier to high capacity. Ride Comfort. In-track switches often consist of a series of articulated straight pieces of guideway that swing back and forth. Passengers will feel such a strong lateral jerk each time the vehicle passes one of the joints that the vehicle will have to slow down for every passage, and there can be four or five straight pieces in each switch. An in-vehicle switch permits guideway branch points to be made with simple smooth curves, maximizing passenger comfort and minimizing jerk loads on the undercarriage of the vehicle. Visual Impact. Articulated in-track switches with their actuators attached greatly increase the visual impact of a switch section. Beyond simply being much larger than a simple branch section, in-track switches have a track leading into empty space, which is a discomforting view for passengers as well as passers by. Cost. An in-vehicle switch has very few moving parts and is very simple and inexpensive to build. An in-track switch is much larger, often consisting of several articulated track sections that move back and forth, and contains many large parts which increase both capital and maintenance cost significantly.
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