Heathrow Airport & Crossrail - Longer Platforms?

[BogiePicker]

Heathrow Terminals 2&3 (CTA); & 5; have platform lengths of 204 and 217m respectively.

Current crossrail 345s have 204m lengths so just fit.

If they go to 11 car we are looking at 250m.

Thus, is there passive scope for longer platforms at Heathrow, or will we need SDO if the 345s gain two extra cars? I think I have seen some somewhat 'pre-built' looking areas whilst entering the platforms, suggesting passive provision has been made, but wd like quantification please.

And it seems Terminal 5 has provison for 2 extra platforms if needs be; would be interested to know how long these can get as well

Thanks

 

[swt_passenger]

I think this has come up before, unfortunately I’m not finding the thread using the search options. I think the consensus was that the Heathrow stations are not that easy to extend.

 

[JN114]

At a Civils Level, CTA and T4 are probably fairly easy; as you say there’s a level of pre-construction done. T5 is probably too constrained - all stemming from the construction methods used and the continued passive provision for future infrastructure immediately west of T5.

T5 is basically in a giant box, with the slab track laid out for a 4 platform (2-island) East-West station, the Northern island only currently fitted with rails and signalling. The terminal foundations were then set around the station and its approaches whilst being built.

Significant complexity at CTA would arise with the signalling - the slab track makes modifications to signalling equipment incredibly difficult. Indeed that is the primary reason why TPWS or axle counters were never fitted down on the Airport Branch, running the additional cabling where no provision had been made when the slab was put in was seen as prohibitive. Whilst ETCS in use nowadays is largely passive on the trackside infrastructure front; longer track circuit sections will be needed at the station for longer trains. At the moment track circuit joints are positioned at the bottom of shafts or adjacent to cross passages to facilitate more space for maintenance and easier access to location cabinets etc. You could deviate from that philosophy, but the civils work to do the cable runs and modify the track slab would be significant; on one of the only bits of railway in the country that ordinarily runs 365 days per year. Heathrow Airport aren’t going to easily tolerate a lengthy closure and service reduction; especially when they see EL overcrowding as in their interest as it pushes more customers to their own “premium” offering.

A Western extension to the Heathrow branch would allow both stations to see 11 car Crossrail trains operating with SDO, and T4 would likely gain the relatively easy proper platform extensions.

 

[BogiePicker]

I think this has come up before, unfortunately I’m not finding the thread using the search options. I think the consensus was that the Heathrow stations are not that easy to extend.

I know, looked myself but could not find. Nothing in any of the technical Heathrow docs either

== Doublepost prevention - post automatically merged: 23 Feb 2024 ==

At a Civils Level, CTA and T4 are probably fairly easy; as you say there’s a level of pre-construction done. T5 is probably too constrained - all stemming from the construction methods used and the continued passive provision for future infrastructure immediately west of T5.

T5 is basically in a giant box, with the slab track laid out for a 4 platform (2-island) East-West station, the Northern island only currently fitted with rails and signalling. The terminal foundations were then set around the station and its approaches whilst being built.

Significant complexity at CTA would arise with the signalling - the slab track makes modifications to signalling equipment incredibly difficult. Indeed that is the primary reason why TPWS or axle counters were never fitted down on the Airport Branch, running the additional cabling where no provision had been made when the slab was put in was seen as prohibitive. Whilst ETCS in use nowadays is largely passive on the trackside infrastructure front; longer track circuit sections will be needed at the station for longer trains. At the moment track circuit joints are positioned at the bottom of shafts or adjacent to cross passages to facilitate more space for maintenance and easier access to location cabinets etc. You could deviate from that philosophy, but the civils work to do the cable runs and modify the track slab would be significant; on one of the only bits of railway in the country that ordinarily runs 365 days per year. Heathrow Airport aren’t going to easily tolerate a lengthy closure and service reduction; especially when they see EL overcrowding as in their interest as it pushes more customers to their own “premium” offering.

A Western extension to the Heathrow branch would allow both stations to see 11 car Crossrail trains operating with SDO, and T4 would likely gain the relatively easy proper platform extensions.

Thanks for the comprehensive answer - over my head as far as the techincal signalling stuff is concerned, but confirms we'll be looking at SDO. So as far as I understand, T5 seems mostly set in concrete, CTA can be physically expanded, but to make the signalling work it would be heavily disruptive because anticipation of this sort of expansion was not necessarily had when building first time around, so we are effectively stuck with a 204m platform length.