Heathrow opened in 1998. The Standard then in force appears to be GC/RT5161 Issue 1 (Issued 1995) - which says:
It does not specifically say 915mm. Issue 2, from 2000, does specify 915mm.
So Heathrow was built to minimise the stepping distance to the conventional floor height of 1,100mm and is grandfathered in. Leading to the present mess. Rail Vehicles Accessibility Requirements was only passed into law in 2010, so there's lots of relatively recent schemes that didn't need to meet it, and thus the same problem exists.
Thank you
@zwk500 , that's very informative. I guess Heathrow just missed out on being at the 915mm standard then. I also guess the Crossrail act being in 2008 means it won't have been covered by RVAR, even if it did meet issue 2 of the GC/RT5161?
I am still at a loss to understand (ie to agree with) that it was better to met the 'standard' of one part of one station (Heathrow) than to comply with the standard standard.
I'm afraid this is where I'm at too. Let's say Crossrail core and trains had been built to 915mm. Yes there'd be a mismatch between Heathrow Express at 1100mm and Crossrail at 915mm for some time, but the GWML platforms would be a lot better off. Furthermore, at some stage, HEx trains will be replaced, and the new trains could be built to match the new standard, and therefore match the Crossrail trains. (And the few platforms at Heathrow could be lowered to 915mm, if they weren't already lowered in prep for Crossrail).
Now though, with the Crossrail core being built to match Heathrow at 1100mm, it would be a lot harder to rebuild Heathrow AND the entire Crossrail core to 915mm, as it is a lot more platforms to alter (and it would require the HEx and 345s to be replaced at the same time with 915mm stock, else again we'd have a mismatch at Heathrow). So instead, could we raise GWML platforms to 1100mm, to match the higher Crossrail core and Heathrow? No - partially because it would break the standard, but mostly because of the freight clearances preventing that, and as others have said, the massive amount of work that would be needed on GWML stations to redo lifts, elevators, staircases, doorways etc.
Maybe there's something I'm not understanding, but it seems to me that in order to avoid having step downs at a few platforms at Heathrow for some period of time, we've instead permanently enshrined steps at a lot more platforms on the GWML for eternity? (Or we'd have to bin off all of the freight on the GWML, which is a non-starter.)
I've responded multiple times on the issues on this thread, trying to address the confusion of others between several related but separate issues.
I don't have any inside information or indeed any information or comment that I haven't posted already.
It appears not to have helped much, so I won't be posting here again.
I appreciate all of your contributions in this thread
@edwin_m , thank you for the information you have added.