Operating and Traffic Rules: Block Working, Signalling and Control
Scope
The operational core: train ordering, block working, signalling and the control desk's records. Sources are the General and Subsidiary Rules, the Operating Manual and the Block Working Manual.
Concepts to master
- Station section versus block section: the station section is the running line within station limits; the block section lies between two block stations.
- Absolute Block System: normally only one train occupies a block section. Line clear is obtained from the block station ahead before despatch, using block instruments; the private number is the authority for the train to enter the block section.
- Colour-light aspects: red stop; yellow caution (prepare to stop at the next signal); double yellow (prepare to stop at the second signal); green proceed. A stop aspect cannot be passed without written authority.
- Interlocking sets points and signals so conflicting movements cannot be signalled.
- Section Controller's tools: the train register and control chart, caution orders, precedence and crossing decisions, and regulation by slowing or detaining trains.
Worked example
A block section is 8 km and permitted speed is 40 km/h. Running time = 8/40 × 60 = 12 minutes. Add about 5 minutes for the rear of the train to clear the block section: 17 minutes. The best one-direction headway is therefore roughly 17 minutes, about three to four trains an hour, before any station detention is added.
Traps that cost marks
- Treating line clear as cancellable after the train has departed the station.
- Reading double yellow as permission to run at normal speed.
- Assuming a private number is needed for shunting inside station limits.
- Omitting the crew's acknowledgement when issuing a caution order.