Why do road over rail bridges always seem to have these sides making it difficult to see the track?

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Tom Williams
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Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by Tom Williams »

Hi there,

Wasn't sure whether to put this here, but I was just wondering why all the railway bridges that I seem to see have these things in the way of the view of the track, like here:
https://www.google.com/maps/@52.0350103 ... K9Oxgw!2e0
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the cheesecake man
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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by the cheesecake man »

I assume it's done to make it harder to jump in front of a train, throw things at it, or electrocute yourself on the wires.
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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by Chris Bertram »

I think it must be a legal requirement to have solid parapets on a bridge over a railway. Travelling westbound on M40 between J15 and J16, you see a long bridge carrying a road over both the motorway and the parallel railway line. For most of its length it has open railings, but over the railway line only, it has solid sides. I suspect that with light signals being so fundamental to railway safety, providing a shield against extraneous lights from motor traffic may have something to do with it.
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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by Jonathan B4027 »

Also makes it a bit harder to drive through, ending up on the tracks. Train detection isn't going to know there is an obstruction.
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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by AndyB »

Don't forget that most road bridges over rail were built from stone, same as rivers. The M40 example (Shrewley Common) is definitely two separate bridges, and the Hereford example doesn't have enough room for containment armco (which, incidentally, is treated as adequate in a couple of places in NI!)

I know of a couple of bridges on the west side of Edinburgh where the sides have been raised quite considerably. I suspect that the reason is vandals throwing stones rather than additional protection against falling onto the overhead wires.
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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by rhyds »

Wasn't it one of the recommendations after the Selby rail crash?
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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by Johnathan404 »

This comes up surprisingly often, and only ever seems to attract speculation, despite us surely having members who have built the things!

Obviously the type of railing depends on the circumstance. Railways with overhead electric wires need to have higher barriers so you can't poke the wires with an umbrella. Bridges in areas with a history of anti-social behaviour may need barriers that are harder to climb or throw things over. Certain road layouts, traffic levels and bridge designs may warrant reinforcement, especially after Selby. Bridges where railways go over roads (not under) will need something to stop ballast being thrown over.

However, none of those points answer the OP's question as to why all bridges have some sort of filter over the railway section. I'm not sure it is any harder to climb than the usual grill, and if it's to reinforce the barrier it would need to be longer.

So this is going to be a guess as well, but it's the only answer I can see that makes sense and applies to all scenarios: it is to stop train drivers seeing a red taillight on the bridge and thinking it's an overhead signal.

This would be the same reason as to why roads that run parallel to railways often have some-kind of filter too.
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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by Chris Bertram »

AndyB wrote: Tue Jul 16, 2019 13:33 Don't forget that most road bridges over rail were built from stone, same as rivers. The M40 example (Shrewley Common) is definitely two separate bridges, and the Hereford example doesn't have enough room for containment armco (which, incidentally, is treated as adequate in a couple of places in NI!)

I know of a couple of bridges on the west side of Edinburgh where the sides have been raised quite considerably. I suspect that the reason is vandals throwing stones rather than additional protection against falling onto the overhead wires.
The M40 bridge I'm thinking of is this one, near Turner's Green - this is a single bridge over both motorway and railway, and you can clearly see the solid section over the railway with open railings either side - the top of the solid section is at the same height as the remainder. The railway is not electrified - it's the Chiltern main line between Birmingham Snow Hill and Marylebone via Leamington, Banbury and Wycombe.
Last edited by Chris Bertram on Tue Jul 16, 2019 16:29, edited 1 time in total.
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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by Brenley Corner »

Would this also be to do in many cases with the protection of the railway from vehicles coming off the bridge (e.g, Great Heck) as well as the other suggestions already made. The M2 near J7 received an additional parapet on the hard shoulder over a railway bridge after this event, for example - Streetview.

Article of interest about this happening at Oxshott on the A244.

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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by Viator »

Thinking of how old (probably still the majority of) railway bridges are, it probably also helped in avoiding frightening the horses.
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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by Big L »

This on the A10 is a good example of a long bridge with a short section with solid sides to go over the railway line. This one on the M23 is a little different.
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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by M4 Cardiff »

I think there is a law dating back from the Victorian times stating that all bridges (I think that station footbridges are exempt and had / have different design requirements) over railways must have solid parapets. Some very early bridges did have lattice parapets or fences, and there were accidents with items/livestock/vehicles ending up on the track. The law also stipulated minimum height requirements for the parapets, which is why these sections are often higher than the adjacent section. I think also that back in the days of steam, the use of solid parapets served to prevent steam burns to persons or livestock on the bridge at the time.

Where there are longer viaducts with the short 'solid' section, the 'solid' section is often just thin sheet metal attached to the existing barriers, but in the eyes of the law, that is required to make it 'solid', even though it does not add to the structural strength.

The post-Selby modifications generally comprised significant extensions to the 5T grade barriers upstream of railway underpasses.
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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by nowster »

How about this footbridge https://goo.gl/maps/KEuZz44CiGzpMtXP7 where half is over the road and half over the rails?
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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by Vierwielen »

High walls (whether or stone or steeel) also rmove the temptation of the driver being distracted by looking down the railway line. This is the same reason (I believe) that drivers of motor cars cannot look at the aeroplanes at Heathrow (See here). (Note, the comera on the Google Car are mounted on the car roof!).
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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by drm567 »

Here's a pdf by Network Rail that explains the current rules. Start on page 30. http://www.bathnes.gov.uk/sites/default ... cation.pdf

And here are a couple of threads in another forum that deal with the historical reasons. As with all (?) forums there is a certain amount of ignorant speculation, but the first two answers in the solid parapet one are essentially on the ball.

https://www.railforums.co.uk/threads/wh ... id.118431/
https://www.railforums.co.uk/threads/br ... on.135720/

Edit - added the Network Rail pdf link
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Re: Why do road over rail bridges always seem to have these sides making it difficult to see the track?

Post by the cheesecake man »

It seems the same rules apply to tram over rail bridges.

Long viaduct taking the tram over various busy roads, with open fences, but just here it passes over a railway and has solid sides.
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