Post by Chris M on Nov 14, 2015 14:49:55 GMT
<<rincew1nd:The initial seven posts in this thread were originally in a thread discussing the Croxley Link.>>
Well, redesigning the station would cost a lot more for starters and an island plaform isn't necessarily cheaper than side platforms. You do need fewer lifts and stairs, but you need a wider formation at either end and then two trackbeds - on embankment/bridges here - rather than one. The whole plan needs to be wider as the lifts and stairs have to be inbetween the tracks not beside them (the station in plan will be very approximately []== shaped) and an island platform ideally needs to be wider than two side platforms for safety.
For Cassiobridge station, the splay would have to start on the bridge/viaduct at the west end which will be more complicated and require more material and thus be more expensive. Structures carrying the track bed need to be much stronger than those carrying platforms, which means they cost more too.
If you look at the DLR in the Royal Docks and elsewhere that was on new land rather than reusing existing infrastructure, and also built to a budget, and you'll see that stations on viaducts almost always have side platforms. The only island platforms above ground on the DLR are:
Nov 14, 2015 12:33:03 GMT trt said:
So... why not an island at Cassiobridge then? I'm considering that the costs of this project are skyrocketing and the whole scheme's economic viability was hanging on a thread anyway. Any measure which could reduce costs would be attractive.Well, redesigning the station would cost a lot more for starters and an island plaform isn't necessarily cheaper than side platforms. You do need fewer lifts and stairs, but you need a wider formation at either end and then two trackbeds - on embankment/bridges here - rather than one. The whole plan needs to be wider as the lifts and stairs have to be inbetween the tracks not beside them (the station in plan will be very approximately []== shaped) and an island platform ideally needs to be wider than two side platforms for safety.
For Cassiobridge station, the splay would have to start on the bridge/viaduct at the west end which will be more complicated and require more material and thus be more expensive. Structures carrying the track bed need to be much stronger than those carrying platforms, which means they cost more too.
If you look at the DLR in the Royal Docks and elsewhere that was on new land rather than reusing existing infrastructure, and also built to a budget, and you'll see that stations on viaducts almost always have side platforms. The only island platforms above ground on the DLR are:
- Tower Gateway (original design) - space reasons (there isn't room for two tracks and two platforms)
- Shadwell - reusing an old viaduct is probably an island for structural reasons and safety adjacent to c2c
- Pudding Mill Lane (original station) - also for space reasons
- Stratford (present terminating platforms) - I suspect there was little cost differential at this site, and an island platform is better for the passengers at a terminus.
- Canning Town (upper level) - the DLR and Jubilee platforms need to be of the same design to allow interchange, and I suspect the infrastructure and staff costs for dealing with interchange between two sets of side platforms (not to mention the disadvantage in terms of passenger provision). I also think that the first DLR station was built as a two-island platform interchange with the North London Line (although I'm not certain).
- Island Gardens (original station) - Island platforms are favoured at terminii from a passengers point of view, but I don't know the rationale for this design here.