"Theo Markettos" wrote

Airtrack's going to have to have a voltage changeover point somewhere.
The
council have suggested it should be at T5 for environmental reasons. I
don't see a problem with them saying that, if it is just a proposal.
There
may well be technical, operational or other reasons which means third rail
is impractical or costly on that stretch but that's for the developers to
make a case for.

Airtrack, as currently planned, will terminate at T5. It has been stated
that the tunnel approach to the station, and the Airtrack platforms at T5
will have to be 25kV OHLE, though I haven't seen an explanation of why this
is so. This being the case, there will have to be a voltage change somewhere
between Staines and T5. It would seem to make sense, in the longer term, for
Airtrack and Heathrow Express and/or Crossrail to link up, with through
running, which of course would require dual-voltage stock and a voltage
change somewhere. An intermediate possibility is for HEx to be extended to
Staines.

Peter