Peter Masson ) gurgled happily, sounding much
like they were saying :

The problem is to ensure that only doors adjacent to the platform open
at stations with short platforms. There is a perceived risk with
relying on the driver's or guard's memory, though signs on short
platforms on the Salisbury - Exeter line seem to me to be an adequate
aid to memory.

They also seem to work very nicely on the Metropolitan Line at Euston Sq
and Gt Portland St.

thinks
Mebbe that's what was meant by GPS & short platforms?