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Introduction Background BiWay
Technical
Impact
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For further information please contact Jim Buick
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Once on the track network each vehicle will be automatically taken to its destination at the nominal speeds of the track sections over which it passes without any driver action. Naturally, a change of destination, diversion for refreshment or emergency input will be accepted by the system and actioned.
Control System
Merging
Route finding
Addresses
These categories are somewhat arbitrary and flexible. One byte should be sufficient for each.
For continent wide coverage, a number of regional track networks may be appropriate with links between them at border crossings.
Routing Tables
Process
Routing Performance
The control system will have three levels; A strategic level to generate, supply and update, route finding data and also perform billing. A tactical level to perform safety tasks, routing, vehicle separation, traffic stream merging and de-merging, and vehicle diversion to rest stops etc, on demand. The vehicle level would also monitor vehicle separation and closing speeds, perform routing with the tactical level, and provide the user interface. The billing system, having access to all the necessary data would be able to charge at different rates for different routes, speeds and times of day. Current technology with some system development is capable of dealing with these requirements. To reduce energy use, the control system will make small changes to vehicle speeds to form them into trains.
Vehicle streams on joining tracks will merge under automatic control with speed adjustments made to create gaps and merge vehicles into them. The system capacity is such that, usually, minor speed adjustments will allow vehicles to interleave. There may however, be sudden fault situations when this will not be sufficient and vehicles on one or other or both sections will have to stop. A programmed deceleration mode with vehicle spacing maintained will generally cope. An emergency stop mode could be implemented if safety studies find it to be necessary.
Routing of each vehicle journey may be biased for speed or economy. No route change is possible at a merging node, so no provision need be made for it. A number of possible routing protocols have been considered. The one described below was chosen for its robustness and performance.
Each node and track exit point has a four level address:
For each track segment between one branching node and the next, there will be a record of both time and cost to traverse, and loading in the form of predicted entry time for each vehicle expecting to use it. If the track segment becomes faulty, it is set as fully loaded. Section time and cost are static data set and amended by network control.
For each vehicle approaching a dividing node, its exits and subsequent branches are checked for the route which best progresses the vehicle towards its goal, taking account of cost/time and congestion. Once selected, the expected entry time for the planned sections is written to the sections' loading tables. It may be worth deleting these records when a change of route is made, but having them deleted by housekeeping once obsolete, may suffice.
This technique provides for continuous, adaptive, route optimisation, which will result in any system faults having only limited local effects by diverting traffic around faults. It enables easy changes of route and accommodates the speed variations involved in train forming and performance optimisation. It does not however, generate an expected time of arrival but this could be obtained from route tables. There will be occasions when selecting the faster route involves greater risk of meeting congestion and greater delay. This could be covered by user selection of Economy, Fast Sure or Fastest.
