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Post by Deleted on Aug 31, 2013 20:19:04 GMT
Just wondcering when the T4 loop was made why the trains from Central London went Hatton Cross to T4 then T123? Why not go Hatton Cross to T123 then T4?
Does it have somethinhg to do with the frequency of trains?
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Post by superteacher on Aug 31, 2013 20:35:48 GMT
I'm assuming that it was easier to build the junction at Hatton Cross with the T4 lone branching off from the westbound line, rather than converging with the eastbound, which would have been necessary if the loop ran in an anti clockwise direction. The line from T4 would have needed to have burrowed under the existing lines, then curved back to join the eastbound. It would have been more difficult, and thus more costly.
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Post by rheostar on Sept 1, 2013 13:53:34 GMT
The original location for T5 was to be served by the same loop, so doing a left on the westbound at Hatton Cross made sense at the time. There's a straight section of track with a pre formed box area where the proposed T5 station was intended to be. So it would have been Hatton Cross, T4, T5 then onto H123.
However, other plans came along with T5 being built miles away from the original location, hence the extension.
Doing a left on the westbound was also a simpler build. Had it gone from HX to H123 then T4, when the track came back to HX it would have had to be built under the westbound road to come onto the eastbound. It would have been an engineering nightmare.
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Chris M
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Post by Chris M on Sept 1, 2013 14:22:42 GMT
Another option would have been to build the crossover somewhere between Acton Town and Hatton Cross, and convert the branch south/west of the crossover to right hand running (like the Central Line is through White City). Potentially less expensive than a flying junction at Hatton Cross but still not cheap with the need to both build the crossover and resignal the line. There is also the question of what benefit an anti-clockwise loop would have over what was built?
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Post by Deep Level on Sept 1, 2013 19:07:14 GMT
The original location for T5 was to be served by the same loop, so doing a left on the westbound at Hatton Cross made sense at the time. There's a straight section of track with a pre formed box area where the proposed T5 station was intended to be. So it would have been Hatton Cross, T4, T5 then onto H123. So journeys to the more popular Heathrow 1,2&3 station would have been even longer, how would that have been the best option? |
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Chris M
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Post by Chris M on Sept 1, 2013 19:27:37 GMT
They would only have been the length of one station stop (~2 minutes) longer, which on a ~50-60 minute journey from Central London is basically negligible.
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Post by railtechnician on Sept 2, 2013 8:18:51 GMT
Another option would have been to build the crossover somewhere between Acton Town and Hatton Cross, and convert the branch south/west of the crossover to right hand running (like the Central Line is through White City). Potentially less expensive than a flying junction at Hatton Cross but still not cheap with the need to both build the crossover and resignal the line. There is also the question of what benefit an anti-clockwise loop would have over what was built? Another option would be to bi-di signal all three roads (Westbound, Eastbound and T4 loop) between Hatton Cross and T123 and then one could 'play trains' to one's heart's content! Seriously as both Hatton Cross (a terminus before T123 opened) and T123 are reversing points it would be possible to run trains wrong road into HX eastbound and all the way through T123 eastbound and around the loop to HX westbound and cross back over to eastbound on the pre T5 layout had bidirectional signalling been installed. I expect the track layout has not changed apart from the alterations for the T5 stub. No need for flyunder or flyover anywhere and probably no impact whatever on services pre T5 and the added advantage of operational flexibility in times of failure! Of course a bidirectional single track loop would've been a nightmare for tourists freshly arriving at T123 and T4 from the airport! I can only imagine the sense of bewilderment that such might've created. |
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