A piece of timber marked with the lengths of various trains has been very useful for final checking of the design. It is planned to run trains with a locomotive and 8 carriages. Some typical train lengths are:
- Class 47 loco + 8 65' carriages: 1275mm
- Class 47 loco + 8 bogie oil tankers: 1133mm
- 8 carriage Eurostar: 1060mm
The design needs to take account of train size for automatic control: the sections between signals need to be slightly larger than the maximum train length and "blocks" for automatic operation will probably follow the signal positions. Each block needs two train detectors: one to sense occupancy, and another to sense the train being at the end of the block so that it can be told to stop.
Some detective work led to the following measurements:
- The minimum distance between the start or end of a block and a point (measured from the rail join to the peco point itself) is 55mm. This is to make sure that a train stops or starts clear of the point, allowing a train on the other track to pass.
- The "normal" part of the block shall be at least 1280mm, to accommodate a maximum length train.
- The "stop zone" part of the block shall be an additional 140mm (this is the zone fed be the second block detector).
- The stopping distance will depend on train speed. The "planned" stopping point is approximately 50mm inside that zone.
