PRT Crossings
PRT systems are usually installed on an elevated level. A PRT system that is installed on an elevated level has grade separated crossings with all other traffic. However, to reduce capital costs the PRT system could be installed at-grade with elevation only at those sections where required. In contrast to other concepts, the underlying (FROG) technology allows the CyberCab system to be (although a-typical for PRT) installed at-grade. At-grade installations are significantly cheaper, but pose additional requirements for crossing other traffic flows.
An at-grade crossing is only realistic if the intensity of both traffic flows is low enough to allow for it. Typically a ‘true’ PRT system will have, at least during rush hours, many vehicles traveling at relatively high speeds (up to 40 km/ph) and short headways (2 to 4 seconds) – creating a heavy flow, requiring grade separated crossings. However, in specific applications – such as resorts – where the flows, speeds and headways are relatively modest, at grade crossings (for pedestrians) can be realized.
Grade separated crossings can be bridges and tunnels. Typically the PRT system will feature a smaller guide way and thus will be routed over or under the track of the other traffic. A bridge is the first option as it is usually cheaper to construct than a tunnel. The safety and evacuation procedures (e.g. in case of fire) for each bridge or tunnel section deserve special attention.
For each application it should be determined (within the safety case) if an at-grade crossing is possible in light of the operating environment and the intensity of traffic flows. For ‘true’ PRT grade separated crossings are almost a standard requirement, while PRT(-like) applications (at e.g. resorts) could benefit from the cost savings realized by being able to use at-grade crossings.