Bridge hits

[compsci]

The one that really makes my (and the entire population of Cambridgeshire's) head spin is number 4 - Stuntney Road, Ely, Cambridgeshire, formerly number 1. This used to have a level crossing next to it for the overheight vehicles, but in this case overheight means that a Police van with blue lights on top will come out without blue lights on top.

The county council spend a fortune building a bypass, including a new bridge over the river and railway. Said fortune was significantly increased when it was realised that the water table was almost at the surface, which is what tends to happen in the Fens. The road under the bridge has now been narrowed down to a single lane with traffic light control (with a reasonable width pedestrian and cycle path taking up the freed up space). As a result the level crossing has been closed. So everyone naively thought that the bridge bashes would stop, but because it is so low most of them are vehicles driven by people who won't normally need to think about the height of their vehicle e.g. supermarket delivery vans and camper vans.

Unfortunately the high water table means that the road can't be dug down to increase the headroom as it would turn into a ford.

[alpinejohn]

Nov 11, 2020 23:01:35 GMT Chris M said:

rincew1nd I know for height restrictions there is always a minimum of 3-6 inches between the bottom of the bridge and the height of a vehicle that is the same height as on the sign (the maximum legal height) and that the measurements are taken at the lowest point (i.e. on pavements if there are any). I imagine that width restrictions are similar but I don't know.

Knowing that last year a vehicle managed to pass unscathed under a low bridge seems a dangerous attitude if you are actually exceeding the official height limit and are relying on making use of the notional leeway built into the max height displayed on signs.

Presumably a bus returning empty to its depot will a bit be taller than a fully laden one, and of course there is always the risk that the road surface may be raised as a result of subsequent resurfacing works which may reduce the available clearance with potentially disasterous results.

If councils seem unwilling to prevent damage to low bridges then it may be time for fresh legislation to equip them all with stand off beam protection located several metres before the actual bridge structure and precisely set at a height which is perhaps just 5 cm above the permitted height limit. This should ensure that actual railway bridges and train traffic will remain unaffected even if truck after truck gets their roof ripped off by the stand off beams.

Perhaps vehicle owners will finally justify the investment in installing quality GPS over height warning systems to all their potentially over-height vehicles.

[cudsn15]

I fully understand the need to safety check each and every bridge hit - but I'm wondering when was the last time a bridge hit actually caused a shift or actual damage to the bridge/running lines?

[Chris M]

The reason for the leeway is to allow for variance in height between laden and unladen condition, new/worn tyres, suspension bounce, etc and measurement accuracy. [url=HSE say that "The stated clearance should be at least 75mm less than the measured height.The stated clearance should be at least 75mm less than the measured height." (source)) This means your idea would need to give 75mm clearance at minimum.

Remember that in all circumstances a vehicle that is the same height as the limit must be able to pass safely beneath the obstruction. This does mean that there being a bit of leeway if you are slightly over the legal limit to pass safely is inevitable. Bridges are remeasured after resurfacing and other things that might affect the clearance.

It is of course illegal to pass a height restriction if your vehicle is greater than that limit, but prosecutions are rare as it's not easy to detect.

The issue with council's not providing beams is primarily a combination of the liability issues I've mentioned a few times (new legislation would need to explicitly address this) and also costs. Councils have very limited budgets and government keep giving them more responsibilities with no commensurate increase in funding. This means highway budgets get squeezed. The council is not significantly impacted in any way by bridge strikes (Network Rail and the vehicle insurers bear the vast majority of the cost) which means that it is very hard for councils to justify any significant expenditure on deterrent or mitigation measures. Again new legislation would need to square this circle - either by funding councils directly, allowing Network Rail (or TfL or whoever else owns the bridge) to pay for councils to install and maintain, or allowing the bridge owner to install and maintain them on council land. Remember Network Rail don't have an unlimited pot of money either.

If there was a single simple fix for the issue we wouldn't be sat here discussing it now, it would have been in widespread use for many years.

[Chris M]

Nov 12, 2020 20:12:34 GMT cudsn15 said:

I fully understand the need to safety check each and every bridge hit - but I'm wondering when was the last time a bridge hit actually caused a shift or actual damage to the bridge/running lines?

After 2 minutes researching this on google, the answer is at least 7 September 2020, possibly 13 October 2020 (bridge is damaged, unclear if the railway lines were).
The same google search suggests that impacts that continue to necessitate speed restrictions after inspections are carried out (i.e. not just precautionary pending inspection) happen at at least 1-2 times per year on average, but I would be surprised if the true figure was more often than that.
Impacts that cause multiple days worth of disruption to the railway seem to happen on average about once every 1-2 years based on the same far from perfect google search.

[johnlinford]

2010 also contains the "alternative style" bridge strike incident in November at Oxshott where a cement mixer managed to crash off the bridge and on to a train... A miracle noone died in that one!

[zbang]

Nov 12, 2020 20:25:14 GMT Chris M said:

Impacts that cause multiple days worth of disruption to the railway seem to happen on average about once every 1-2 years based on the same far from perfect google search.

Possibly skimming RAIB report titles would also yield some info, I expect they'd look at anything like that; not offering to do so at the moment.

(Topic drift- whatever happened with that 100m+ section of brick wall that fell down on some tracks?)

[Chris M]

Nov 13, 2020 0:08:40 GMT zbang said:

Nov 12, 2020 20:25:14 GMT Chris M said:

Impacts that cause multiple days worth of disruption to the railway seem to happen on average about once every 1-2 years based on the same far from perfect google search.

Possibly skimming RAIB report titles would also yield some info, I expect they'd look at anything like that; not offering to do so at the moment.

I've looked through the index of all the RAIB reports published to date and believe the only incidents of road vehicles striking railway bridges the RAIB have investigated have been:

• Oxshott (cement mixer fell off overbridge onto a train)
• Froxfield (lorry reversed into parapet of overbridge, train collided with fallen masonry)
• Barrow-upon-Soar (train collided with a footbridge that had been knocked down by the raised body of a tipper lorry on a road parallel to the railway)

This is not surprising because the RAIB's remit only includes incidents where there are (or might be) new safety learnings for the railway industry. Bridge strikes are common and the safety implications are well known to the railway, and the processes to be followed after they occur are at this point routine (stop trains until the bridge has been examined by a competent person; block lines and/or impose speed restrictions until any necessary repairs have been completed). As there has not been any incidents causing death or injury on the railway as a result of road vehicles striking bridges under the railway in at least the 15 years (the RAIB was established in 2005) it seems these processes are working.

[35b]

Nov 13, 2020 1:36:24 GMT Chris M said:

Nov 13, 2020 0:08:40 GMT zbang said:

Possibly skimming RAIB report titles would also yield some info, I expect they'd look at anything like that; not offering to do so at the moment.

I've looked through the index of all the RAIB reports published to date and believe the only incidents of road vehicles striking railway bridges the RAIB have investigated have been:

• Oxshott (cement mixer fell off overbridge onto a train)
• Froxfield (lorry reversed into parapet of overbridge, train collided with fallen masonry)
• Barrow-upon-Soar (train collided with a footbridge that had been knocked down by the raised body of a tipper lorry on a road parallel to the railway)

This is not surprising because the RAIB's remit only includes incidents where there are (or might be) new safety learnings for the railway industry. Bridge strikes are common and the safety implications are well known to the railway, and the processes to be followed after they occur are at this point routine (stop trains until the bridge has been examined by a competent person; block lines and/or impose speed restrictions until any necessary repairs have been completed). As there has not been any incidents causing death or injury on the railway as a result of road vehicles striking bridges under the railway in at least the 15 years (the RAIB was established in 2005) it seems these processes are working.

I wish I shared your confidence. The bridge where the A52 crosses under the ECML in Grantham is regularly hit, and line speed is over 100mph. Network Rail, LNER and the police are practiced at dealing with these, but with the best will in the world, there is a time lag between incident and notification. My fear is of what happens when there isn’t time to put precautions in place, and it is a seri impact, not just (as is usually the case) a low speed clout of a curtain sided trailer.

[class411]

Nov 13, 2020 8:20:28 GMT 35b said:

Nov 13, 2020 1:36:24 GMT Chris M said:

I've looked through the index of all the RAIB reports published to date and believe the only incidents of road vehicles striking railway bridges the RAIB have investigated have been:

• Oxshott (cement mixer fell off overbridge onto a train)
• Froxfield (lorry reversed into parapet of overbridge, train collided with fallen masonry)
• Barrow-upon-Soar (train collided with a footbridge that had been knocked down by the raised body of a tipper lorry on a road parallel to the railway)

This is not surprising because the RAIB's remit only includes incidents where there are (or might be) new safety learnings for the railway industry. Bridge strikes are common and the safety implications are well known to the railway, and the processes to be followed after they occur are at this point routine (stop trains until the bridge has been examined by a competent person; block lines and/or impose speed restrictions until any necessary repairs have been completed). As there has not been any incidents causing death or injury on the railway as a result of road vehicles striking bridges under the railway in at least the 15 years (the RAIB was established in 2005) it seems these processes are working.

I wish I shared your confidence. The bridge where the A52 crosses under the ECML in Grantham is regularly hit, and line speed is over 100mph. Network Rail, LNER and the police are practiced at dealing with these, but with the best will in the world, there is a time lag between incident and notification. My fear is of what happens when there isn’t time to put precautions in place, and it is a seri impact, not just (as is usually the case) a low speed clout of a curtain sided trailer.

Surely they can have automatic monitoring in places like that.

All you need is a laser pointed at a target alongside the rails (bridges are rarely curved). If it stops registering the signals go red.

Pretty cheap, very fail-safe, and probably not much chance of false positives.

[35b]

Nov 13, 2020 8:55:13 GMT class411 said:

Nov 13, 2020 8:20:28 GMT 35b said:

I wish I shared your confidence. The bridge where the A52 crosses under the ECML in Grantham is regularly hit, and line speed is over 100mph. Network Rail, LNER and the police are practiced at dealing with these, but with the best will in the world, there is a time lag between incident and notification. My fear is of what happens when there isn’t time to put precautions in place, and it is a seri impact, not just (as is usually the case) a low speed clout of a curtain sided trailer.

Surely they can have automatic monitoring in places like that.

All you need is a laser pointed at a target alongside the rails (bridges are rarely curved). If it stops registering the signals go red.

Pretty cheap, very fail-safe, and probably not much chance of false positives.

They may, I don’t know. At the speeds involved, that still only gives me limited comfort.

[norbitonflyer]

Nov 13, 2020 1:36:24 GMT Chris M said:

Nov 13, 2020 0:08:40 GMT zbang said:

Possibly skimming RAIB report titles would also yield some info, I expect they'd look at anything like that; not offering to do so at the moment.

I've looked through the index of all the RAIB reports published to date and believe the only incidents of road vehicles striking railway bridges the RAIB have investigated have been:..............
.

A long time ago, but I remember this one from 1978. (Digger on a low loader hit a bridge just as a train was approaching, and derailed it.

Despite one carriage going down the embankment and another ending up on its side there were only minor injuries.

The same excavator had been driven under the bridge before, but on this occasion, after loading and unknown to the driver, the jib had been operated and not stowed properly.

The lorry driver ran along the track to warn oncoming trains (choosing the direction with the poorer sightline), but unfortunately the train came from the other direction.

The accident happened on a Friday morning. By Sunday afternoon the damaged span had been replaced and the line re-opened!

[class411]

Nov 13, 2020 9:06:08 GMT 35b said:

Nov 13, 2020 8:55:13 GMT class411 said:

Surely they can have automatic monitoring in places like that.

All you need is a laser pointed at a target alongside the rails (bridges are rarely curved). If it stops registering the signals go red.

Pretty cheap, very fail-safe, and probably not much chance of false positives.

They may, I don’t know. At the speeds involved, that still only gives me limited comfort.

They may have civil engineering solutions such as having the track 'float' on the bridge structure.

[Chris M]

Nov 13, 2020 8:20:28 GMT 35b said:

I wish I shared your confidence. The bridge where the A52 crosses under the ECML in Grantham is regularly hit, and line speed is over 100mph. Network Rail, LNER and the police are practiced at dealing with these, but with the best will in the world, there is a time lag between incident and notification. My fear is of what happens when there isn’t time to put precautions in place, and it is a seri impact, not just (as is usually the case) a low speed clout of a curtain sided trailer.

That bridge has sacrificial beams adjacent to it. On the east side it's about 2 metres before the bridge goo.gl/maps/HpkA3UNKXgjoPiEB6 on the west about a metre goo.gl/maps/dKbKURV4Mtf6s4Wj6

[John Tuthill]

Nov 11, 2020 10:30:09 GMT billbedford said:

Nov 10, 2020 16:40:12 GMT djlynch said:

The signal is tied in to the detectors for the warning sign. On the videos the lights go yellow (amber) at the same time the warning sign lights up, but American laws generally allow entering the intersection up to the instant the red light comes on and a lot of drivers will keep going even if they get there a second or two too late, so it's not as effective as it could be.

But, then there's the old joke:

What do the colours on traffic lights mean?

Red = Stop

Green = Go

Amber = Go faster

"Traffic lights? What traffic lights?"

[alpinejohn]

When it comes to bridge strikes I really do not think there is great merit in focusing attention on somehow automatically monitoring the track alignment and triggering the signals to red if/whenever they happen.

Basic physics cannot be avoided - a HST travelling at 125 miles per hour covers 176 feet of track every second! Also..

Mr. Redwood

To ask the Secretary of State for Transport what the safe braking distance is of a 125 mph diesel train to stop from maximum speed. [81247]


Mr. Spellar
The Health and Safety Executive have advised that, assuming a standard-load diesel commuter train, on a flat gradient with good rail/wheel adhesion conditions, approximately:

2,568 metres using defensive driving brake application;
1,713 Metres using full service brake application; and
1,283 Metres using with an emergency brake application.



So to bring that HST to rest using the full emergency brake application would take at least 4203 feet (assuming dry rails and an alert driver) - (sorry I still think in imperial measurements).

So what happens if a dozy driver smashes his overheight truck into a bridge travelling fast enough to distort the track. Your automatic laser monitoring system will instantly detect the problem and set signals to red. BUT it will really only help if can garantee that there are no trains within 0.8 miles of the bridge - as there is a risk that any trains within that distance are going to reach the defective track even using maximum braking.

Trains just cannot defy momentum.

The answer must be to bite the bullet and make sure we prevent any over-height vehicles hitting the bridge in the first place. Sadly imposing massive fines and driving bans are inherently "after the fact" sanctions - they do not prevent idiot drivers potentially killing rail passengers.

Sadly those RAIB statistics suggest it is really only a matter of time before we have yet another Ladbrook Grove/Hatfield type disaster moment which will finally get Government to properly address this risk.

[norbitonflyer]

Nov 13, 2020 9:16:18 GMT norbitonflyer said:

Nov 13, 2020 1:36:24 GMT Chris M said:

I've looked through the index of all the RAIB reports published to date and believe the only incidents of road vehicles striking railway bridges the RAIB have investigated have been:..............
.

A long time ago, but I remember this one from 1978. (Digger on a low loader hit a bridge just as a train was approaching, and derailed it.

Also this one in 1975 (in Ireland, so not investigated by the RAIB but by its Irish counterpart). Similar circumstances except that there were no warning signs, and more serious consequences (five fatalities).

[zbang]

Nov 13, 2020 10:36:41 GMT alpinejohn said:

When it comes to bridge strikes I really do not think there is great merit in focusing attention on somehow automatically monitoring the track alignment and triggering the signals to red if/whenever they happen.
[...]
So what happens if a dozy driver smashes his overheight truck into a bridge travelling fast enough to distort the track. Your automatic laser monitoring system will instantly detect the problem and set signals to red. BUT it will really only help if can garantee that there are no trains within 0.8 miles of the bridge - as there is a risk that any trains within that distance are going to reach the defective track even using maximum braking.
[...]
The answer must be to bite the bullet and make sure we prevent any over-height vehicles hitting the bridge in the first place. [...]

You're mixing the apples of real-time action with the watermelon of active prevention.

No, a red signal will not stop the train that's already within stopping distance of the problem, but then this is true for anything that will put up a Danger (like a broken rail).  The purpose is to alert the trains (and signalers/controllers) that there is a problem ahead (like a broken rail). And even if the train can't fully stop, any energy dissipated in braking won't have to be dissipated in a crash. (Railways in areas of avalanche or rock slides often spend a fair bit know that one has occurred, better to send out a plow or digger to clean up than send a goods train at 60kph.)

And we know from long experience that even with training, fines, etc, humans make mistakes. A simple (and relevant) example is Correct Side Door Enable- a trained driver would never (I hope) intentionally open the wrong side, but it's happened enough to warrant adding CSDE to the trains. Heck, most of signaling is to prevent things that shouldn't happen anyway.

[countryman]

Nov 12, 2020 20:13:44 GMT Chris M said:

It is of course illegal to pass a height restriction if your vehicle is greater than that limit, but prosecutions are rare as it's not easy to detect.

I don't believe that it is automatically for an overheight vehicle to pass a restriction. It depends on the signage. An example is Eastbury Road at Bushey. The height limit is 14' 3", but for years Routemasters and RTs, both 14' 6", run under it regularly. When a bus running day in Watford was operated a few years ago, the signage for the bridge was triangular warning signs, and Routemasters and RTs ran under it on that day. The next time the event was held the signs had been changed to round prohibition signs, so then it became illegal to run them under the bridge and only single deckers could run. Hopefully you should be able to see the current signs on Streetview.


www.google.co.uk/maps/@51.6463675,-0.3858067,3a,75y,71.35h,90t/data=!3m7!1e1!3m5!1sUS0oxj7yTcjC30dqkyxIXA!2e0!6s%2F%2Fgeo0.ggpht.com%2Fcbk%3Fpanoid%3DUS0oxj7yTcjC30dqkyxIXA%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D61.455505%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656?hl=en&authuser=0

Note: You may need to copy the URL above into Google Maps to view.

[Chris M]

Yes, there is a difference between a height warning (triangular sign) and height restriction (circular sign). I think warnings should be placed in advance (e.g. on directional signage) with restrictions placed at the point of no return before the obstacle with limited clearance, however there are still bridges that are signed only with warnings. I don't know what the criteria for a restriction actually is.

[croxleyn]

Nov 16, 2020 22:06:20 GMT countryman said:

www.google.co.uk/maps/@51.6463675,-0.3858067,3a,75y,71.35h,90t/data=!3m7!1e1!3m5!1sUS0oxj7yTcjC30dqkyxIXA!2e0!6s%2F%2Fgeo0.ggpht.com%2Fcbk%3Fpanoid%3DUS0oxj7yTcjC30dqkyxIXA%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D61.455505%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656?hl=en&authuser=0

Note: You may need to copy the URL above into Google Maps to view.

If you are not aware, the clock symbol/icon next to the location allows you to look back at historical shots:

www.google.co.uk/maps/@51.646369,-0.3858008,3a,75y,71.35h,90t/data=!3m7!1e1!3m5!1sb4lDcbmLYm78Xv7Fi1o3PQ!2e0!5s20080801T000000!7i13312!8i6656?hl=en&authuser=0

shows the triangular warning sign in 2008: the next in 2012 shows the round mandate!

[roythebus]

A couple more incidents, one was a double decker in Cambridge where the road apparently is used by single and double decks, runs parallel to the railway, doube decks must turn before the road bridge over the railway and busway. One didn't the other week and neatly took the top clean off the bus. Who on earth would design a busway which could be used by full height buses to have a ow bridge part-way along it?

My partner is a pilot for a London operator and was piloting on the Watford-Harrow job a while ago, going under the bridge at Bushey mentioned above. She told the driver to stop before the brige, he asked why, then she looked back down the bus and didn't see any stairs. She wasn't used to piloting single decks!

More recently an agency driver with a new pilot missed a turn at Bow and continued along the new A12 next to the Central Line. Being a new A road it is built with full height bridges. Howver, some 50m from that road is a bridge on the parallel Grove Green Road where the GOBLIN crosses the road. That cloked up on the iBus system, warning, low bridge. He correctly stopped and took the next exit from that road. the trouble was the road he chose to take took him back along Grove Green Road towards the low bridge. Luckily he stopped well before the bridge and no damage was done, but beacause he ignored advice from the office he was not offered any more work. But it goes to show that the "best" navigation systems can be wrong even when they're right if that makes sense. Had he continued on the A12, he would have been ok.

Edited to add that in the early 1970s the bridge past the Kew Records Office, part of the south circular road got moved by an overheight lorry. They had to put single line working into operation between Gunnersbury and Richmond. I was spare guard that day so got a job as pilotman on the District Line train that was trapped there for a couple of days. The bridge was subsequently rebuilt, road lowered and track level raised to make the bridge clear for 4.5m.

[Chris M]

Nov 23, 2020 22:27:19 GMT roythebus said:

More recently an agency driver with a new pilot missed a turn at Bow and continued along the new A12 next to the Central Line. Being a new A road it is built with full height bridges. Howver, some 50m from that road is a bridge on the parallel Grove Green Road where the GOBLIN crosses the road. That cloked up on the iBus system, warning, low bridge. He correctly stopped and took the next exit from that road. the trouble was the road he chose to take took him back along Grove Green Road towards the low bridge. Luckily he stopped well before the bridge and no damage was done, but beacause he ignored advice from the office he was not offered any more work. But it goes to show that the "best" navigation systems can be wrong even when they're right if that makes sense. Had he continued on the A12, he would have been ok.

Yes, false warnings like this are a problem because drivers on routes that are subject to them will get used to ignoring the warning and then one time it wont be false. Going off topic for a moment, it's also why vehicles aren't yet routinely limited to the speed limit of the road they are on and such systems are not a panacea for solving road traffic incidents (as many militant cyclists and anti-car campaigners) are want to claim) - there are far too many occasions when the speed limit "read" is for a nearby road with a different limit.

[johnlinford]

There's a railway bridge in Wandsworth where the warning sign used to activate well before a vehicle is too high - it was a right of passage to be scared by this by a local company as a passenger in their 7.5T trucks that activated the warnings but didn't break the height limit.

Warnings and alerts given that aren't valid devalue them when they are.

[compsci]

Nov 23, 2020 22:27:19 GMT roythebus said:

A couple more incidents, one was a double decker in Cambridge where the road apparently is used by single and double decks, runs parallel to the railway, doube decks must turn before the road bridge over the railway and busway. One didn't the other week and neatly took the top clean off the bus. Who on earth would design a busway which could be used by full height buses to have a ow bridge part-way along it?

This is a little more complicated than that, and most likely related to very recent service changes. There are two completely separate busways in Cambridgeshire. One runs from St Ives along what was the Cambridge to St Ives railway, passing a number of villages until it reaches a junction at Orchard Park (a housing development on the north edge of Cambridge, south of the A14 but not politically part of Cambridge). It splits here, with one arm going through Orchard Park to Histon Road and the other going past the Science Park to Milton Road. Buses then join the road network to reach the city centre. This busway is essentially a bus bypass of the A14. It is used by both single and double deckers. Until 1 November 2020 all the double deckers terminated via a loop of the city centre.

Single decker busway buses (and the double decker route C from 1 November, do you see where this is going?) continue on road to the railway station. Single deckers pass through the bus station and then enter a busway only (but not guided) road (straight ahead at this junction), while the double deckers terminate and rejoin the road by turning right at the same junction. The busway only road goes through a newly built underpass that was carved out of the abutments of the bridge that carries Hills Road (the main road from the city centre to Addenbrooke's hospital and the south) over the railway. This underpass took months to build as it was effectively a reconstruction of part of the bridge. It can only take single deckers, and this is where the bridge strike happened. This busway then continues alongside the railway (passing but not stopping at Long Road sixth form college, relevant later), before diverging away slightly to the west, where there is a junction, with one arm crossing the railway to Addenbrooke's hospital and the other following the former Cambridge to Bedford railway into a cutting to Trumpington park and ride. The width of this cutting means that the busway goes to a single track here, with an unguided transition point between the single and double track sections. There have been two serious derailments here, with the buses ending up on their side in the bushes, having gone straight over the cycleway that parallels the track.

We know that the bus involved in the bridge strike was a double decker route C, which given the time of day was most likely scheduled to travel by road from the railway station to Long Road sixth form college. So it had to turn right at the junction along with all the other ordinary buses leaving the railway station to go south. By now it should be obvious where the potential for confusion lies. I expect that a multitude of flashing signs will be installed soon.