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Discussion in 'Infrastructure & Stations' started by sidmouth, 12 Jul 2012.
So whats wrong with OD crossings?
Good point, I hadn't considered that. I have used that track on foot or bicycle when the crossing has been closed for maintenance, but I admit I am not a standard pedestrian, and am happy to walk in the road. Of course, the Eastern crossing is the least busy, so it might not be worth doing anything with it at all, or do the road, and add the lights as you suggest, but leave the crossing in place as a CCTV controlled full barrier one, as you could see if it was closed and take the diversion only if necessary. Of course that might be taking everything too far and too expensive.
The Eastern Crossing might be the least used but possibly the cheapest to address and also ameliorates the multi-crossing interaction issues some what.
[Pedant on]*over[pedant off] The bridge is also 'a bit low' at 3.5m and would need to be raised, or perhaps more likely the road lowered. As the road is almost certainly at a lower level than the Great Ouse river some will now have a sharp intake of breath!
The farm track joins Queen Adelaide Way far too close to the rail bridge to give adequate sighting. Any road junction would need to be futher south, possibly with a roundabout for extra safety.
None of this solves the issue of extra crossing barrier downtime associated with (even more) trains using a combined route.
That's always been my impression, since the public meeting. I assume there is a formula for network rail to use for the distance between crossings, expected road traffic flow and expected closed time, to give an idea of interaction problems. I wonder what it says in this case?
I wouldn't change the bridge clearance, it isn't too much of that traffic anyway. If anything, the link would increase traffic, as the main destination for lorries in the area is the depot on the road south. If the crossing was left open as full barrier other lorries could either wait or take alternate routes. From Mildenhall way, they could stay on the A1101 and down from Littleport, from the south, use the A142.
The junction could move south, but I would expect the east/south path to be made the mainline, so sight-lines wouldn't be too much of a problem. But knowing the council round here, a roundabout would probably be used, even if it isn't needed.
The simplest thing to do these days (and probably most useful is probably a big wide spread APRN traffic survey for a fortnight to see what all the interactions are and what journey people are actually making
Survey has already been done!
Link up-thread at #86, which seems now non-working.
They did a survey at the end of 2016:
I remembered reading about it a while ago, but looking at it again shows some interesting things. The north/south route that doesn't use any of the crossings is the biggest route, so maybe a lights controlled under-bridge would not be a good idea. It is also odd that they separated the flows from Ely Road and King's Avenue, which has measured over 16% of the cars surveyed which are just going from the housing into Ely and back on the easiest route, without using the crossing at all. That might skew the figures a bit.
There lack of parallelism in the junctions is another factor with ramifications not as straightforward as at first glance. It may limit the total number of trains possible to run through the junction, but it also prevents a number of movement combinations that with double junctions could pass each other in the area, using the same road closure. That becomes especially important if the crossings were converted to MCB with much longer warning time.
I assumed the improvements were going to at least put a ladder in between the Peterborough and King's Lynn lines. That, and a crossover north of the Norwich junction would allow a lot of simultaneous moves. Am I right in reading the track diagram as showing all the platforms are bi-directional all the way through to the Ely South junction and crossovers?
Traksy suggests that to be the case:
Here's my development of the track reroute idea suggested above. This would involve reusing the old March-bound alignment for a rerouted road heading south to a new bridge over the junction into the Potter complex then exiting over their river bridge to Queen Adelaide Way. All three crossings would be eliminated for most traffic but the eastmost one would be retained for any local traffic that was overheight. It might be a MCB-OD that was normally closed to road traffic and opened on demand for vehicles that need it. The middle crossing might retain a pedestrian facility, perhaps a footbridge.
Yes, full bi-di between Ely South (actually "Dock") Jn to Ely North Jn via all platforms, plus the Down Peterborough line as far as Ely West Jn. Use restricted only via available crossovers (e.g. Using Platform 1 in the Up direction needs a wrong-direction move all the way from North Jn)
Watching on OpenTrainTimes maps the signallers creatively use the bi-di even in normal running is fascinating, especially to get around some of the signalling controls.
Also you can route an Up train via the Down Cambridge line to just past the end of the Down Goods Loop towards Cambridge.
I understand the piles for the bypass viaduct are as deep as Ely Cathedral is tall, to give some engineering context....
Gosh it will be as deep as [insert ancient monument here] is tall soon!
Cambs CC quoted 2/3rds height of Ely Cathedral in their opening press release:
That would make the pile depth 44m.
The 'ground' as stated in lots of places is to say the least difficult. But it is what it is.
Around Ely North the railway is close to the edge of the Kimmeridge Clay and may not be quite as bad to the west of the line. But to the east ..... ?
Geological survey map:
Just before they opened the bridge to traffic they let people walk its length for a day. There was an information board present on that day which said that it was the full height of the structure, measured from the top of the bridge to the bottom of the foundations, that was the same height as the cathedral.
Looking at your map I thought I saw or heard something suggesting that NR was already looking at a route similar to the red line on your picture.
I did a google car view along the road that refers to Queen Adelaide and was surprised to see all three crossings were of the AHB variety. Firstly is this correct and that Google car is out of date? If its still in date I'm surprised they haven't been made full barrier Crossing with CCTV supervision or Full Barriers as MCB OD Level Crossings.
No need really. The crossings at Peterborough, Lynn, & Norwich Roads (as they where known) work perfectly well as AHBs.
Really? If I could find that, it would make good reading, and probably make the residents a bit happier.
Google isn't out of date, the only thing that might be new is the traffic enforcement cameras to ticket those who go through the crossings while flashing. The problem is that if they put MCB crossings in, they would be down way too much, and cause massive problems on the road, and possible queues from one crossing blocking another. Full barriers were one of the things they talked about at the public meeting last year, when considering increasing the number of trains through the area.
The red line would be very much slower than the existing; 20mph at most. This means that the 700m long container trains would take an extra couple of minutes to clear the junction, which in turn would actually reduce capacity.
The crossings' renewal and replacement by something safer is no doubt the primary factor driving the project to look at different options. Growth of traffic, both road and rail, and development in the area will have made the risk of traffic at one crossing blocking back to the next higher, and this is very dangerous with AHBCs. MCBs, with their much longer warning time, would increase the likelyhood of block-back, but if it happened the crossing wouldn't clear, so trains would be delayed instead of road vehicles being hit. Even if they can't all be eliminated, a reduction in the number of crossings here will definitely improve matters.
A wider curve looks plausible. At least 500m radius as shown here:
That is bad ground! The worst I've had to do is 24m for a 2 story building...
(The aim was foundations reusable for 200+ years)
Trowse Bridge, it is not such a bottleneck as people seem to think, two trains can follow within 1 minute of each other fairly easily, it can seem a bit of a log jam due to some of the timings of trains, and of course if they are on time! the 1Rxx ex Norwich only needs to be 1 late, and that will affect the 1pxx to Liverpool Street.
This is the average 2 hour level of traffic:
PASS 10:58 1R82 NORWICH
PASS 11:01 1P31 NORWICH
PASS 11:06 1L04 NOTTINGHM
PASS 11:25 1P16 LIVERPLST
PASS 11:28 1K66 CAMBRIDGE
PASS 11:31 1P33 NORWICH
PASS 11:41 1K73 NORWICH
PASS 11:46 1P18 LIVERPLST
PASS 11:58 1R86 NORWICH
Even with the propose /possible additional London's there will still be space for more, it will be late running that slows it down !
When the North Walsham tanks run, that takes a chunk out of the availability, due to the speed that it has to run onto the Wensum Curve, and the approach controlled signal (GPL)
It was mentioned that the inbound 1Lxx get held at Trowse quite a lot, however this is not the case unless A) It is early approaching the Junction, which is quite often, or B) the up IC service is late for whatever reason, and even then the IC could run via the DL allowing the EMT to approach the Bridge.
As DK says, Trowse was and still is a marvel when you think about what it does, (OHL feed and isolation when swung) and it's been there since 1987, just a shame the electronics to make it swing were on the dodgy side !
Chettisham, a couple of miles west of Queen Adelaide was converted from AHB to MCB-OD about 18 months ago. The level crossings at Quen Adelaide are still AHBs.
Even so, you’d be lucky to get 40mph through there, probably 30.
Also building new railway will face the same challenge as new road. There will need to be deep foundations.
Yes, but that one stretch of lines foundations might be cheaper than a road that will in addition need at least 2 bridges over rail, and one over the river. Is 40 a problem? I have never seen a freight train move fast over the Peterborough crossing anyway, and all passenger trains stop at Ely, except one sunday service which uses the West Curve, so has to be slow for that.
I know there is no easy solution to this stretch of road, and I do want the rail service to be increased, so something has to give, but I think it quite unlikely they are going to pay the same or more as the Ely South bypass to fix a short section of road that has only 10,000 trips a day, so the road is going to get a bit worse. As long as they can remove some of the biggest risks.
Very much doubt Potters would be ok with such a huge structure going through their property....and if you are going to go with the expense of a large raised road and various bridges why not do it north of the current ahbs where there are fields and avoid the need and cost to mess about with the track alignment.
Ely North Junction is 50mph for most routes except Down Peterborough which is 60mph, and to/from West Curve which is 25mph.
If you reduce the speeds through the junction any gains made from doubling the junction and/or closing the level crossings will be more than cancelled out by the longer times for trains, particularly the long liners, to pass over the junction.
I have no idea why people are so surprised by the ground conditions around Ely, or to give it it's olde name, Isle of Ely.
Yes, Ely used to be an island surrounded by water ! (Which was drained and created the "Fens", leaving very black peaty soil).