Clive D. W. Feather wrote:
In article . com,
TheOneKEA writes
All Central Line trains are driven
automatically by a central control computer (in simple terms).
Not quite. I used to think this too but an AET who works on the Central
informed me that the ATO function is locally controlled from the
trackside SERs, which implies that the central computers are merely a
regulatory and supervisory system (i.e. a souped-up programme machine);

Neither is quite correct.

The ATO/ATP function is on the train and controlled by the driver:
- in ATO mode the driver presses "start" and ATO drives the train under
the restrictions set by ATP;
- in Coded Manual the driver drives the train himself under the
restrictions set by ATP.
In both cases the train is informed of the permitted speed limit in the
current and next blocks by codes in the rails. These are sent by the
trackside units. At stations, a docking beacon sends the train details
of the line ahead and, in ATO mode, whether or not to stop at the next
station and whether to go "full welly" or coast at various places to
increase the running time (and so space out trains).

The central computer:
- sets routes for the trains at junctions (like a programme machine);
- instructs the beacons to issue "don't stop" and "coast" instructions.


Actually, TheOneKEA's post is slightly closer to reality.
While the decision to coast is made by the control system, the facility
isn't used with ATO. Hence the system is independent of the signalling
control system in day to day operations.

TJC (currently Acting Senior ATO Data Engineer, Central Line)