M3 Low Bridge

[Micro The Maniac]

Not seen this reported previously...

A footbridge across the M3 near to junction 3 (Bagshot/Lightwater) is to be demolished this weekend, with a full closure over the weekend.

The bridge is an original feature, having been in place since the M3 opened... but it has suddenly been found to be only 16'4" and not the required 16'6" - but only in the outside lane

https://nationalhighways.co.uk/our-road ... ootbridge/

I'm puzzled why (a) it's only just been found to be under-height, and (b) why demolition is the only option, as opposed to a permanent height limit in lane 4? Especially when a replacement footbridge is not going to be in place before Autumn 2025!

[jnty]

Is there precedent for a lane-based height restriction on any other motorways in the UK? It seems as though expecting perfect compliance to this unusual restriction might be too much to ask, especially on a route in the South which leads to Channel ports, and the consequences could be quite severe. An over-height vehicle is unlikely to be in the outside lane legally anyway and, charitably, might end up there 'accidentally' (eg. taking evasive action after being cut up.) Once you've acknowledged the risk, I think a full lane closure might seem like the only reasonable mitigation.

Having said that, if it's not been hit yet...

[AndyB]

Also for any closure of Lane 1, even if Lane 2 is still open.

[Conekicker]

Not seen this reported previously...

A footbridge across the M3 near to junction 3 (Bagshot/Lightwater) is to be demolished this weekend, with a full closure over the weekend.

The bridge is an original feature, having been in place since the M3 opened... but it has suddenly been found to be only 16'4" and not the required 16'6" - but only in the outside lane

https://nationalhighways.co.uk/our-road ... ootbridge/

I'm puzzled why (a) it's only just been found to be under-height, and (b) why demolition is the only option, as opposed to a permanent height limit in lane 4? Especially when a replacement footbridge is not going to be in place before Autumn 2025!

Most likely the carriageway has had one or two overlays since it was originally built, with a subsequent loss of headroom.

If this is the case, then quite frankly a weekend closure, where the carriageway level is reduced by, say, 75-100mm over a distance of 100m or so either side of the bridge would be a better solution. Any safety barrier alterations could then be done during the week via lane closures. That would be massively cheaper than demolishing and replacing the bridge.

This lack of headroom problem has happened before on the M1 near Woolley Edge services, on the southbound, at the overbridge just before the exit slip. The headroom over lane 3 became sub-standard due to overlays. Easily fixed by a planer and a new wearing course, or surface course as it's now called I believe.

Edit: Top tip for scheme designers - CHECK THE ****ING HEADROOM!

[WHBM]

That section was rebuilt not too long ago for ALR. My guess is the footbridge was previously just compliant, the resurfacing etc added two inches to the carriageway, and it has only just been realised.

Has it been struck ?

[Conekicker]

Is there precedent for a lane-based height restriction on any other motorways in the UK? It seems as though expecting perfect compliance to this unusual restriction might be too much to ask, especially on a route in the South which leads to Channel ports, and the consequences could be quite severe. An over-height vehicle is unlikely to be in the outside lane legally anyway and, charitably, might end up there 'accidentally' (eg. taking evasive action after being cut up.) Once you've acknowledged the risk, I think a full lane closure might seem like the only reasonable mitigation.

Having said that, if it's not been hit yet...

An overheight vehicle could very easily be in the offside lane if maintenance works meant it was the only lane left open to traffic.

[wallmeerkat]

Is there precedent for a lane-based height restriction on any other motorways in the UK?

Not a motorway but the NI A1 dual carraigeway has a restriction on the offslip lane at Dromore - https://www.google.com/maps/@54.4144681 ... &entry=ttu

[Bryn666]

Not seen this reported previously...

A footbridge across the M3 near to junction 3 (Bagshot/Lightwater) is to be demolished this weekend, with a full closure over the weekend.

The bridge is an original feature, having been in place since the M3 opened... but it has suddenly been found to be only 16'4" and not the required 16'6" - but only in the outside lane

https://nationalhighways.co.uk/our-road ... ootbridge/

I'm puzzled why (a) it's only just been found to be under-height, and (b) why demolition is the only option, as opposed to a permanent height limit in lane 4? Especially when a replacement footbridge is not going to be in place before Autumn 2025!

Most likely the carriageway has had one or two overlays since it was originally built, with a subsequent loss of headroom.

If this is the case, then quite frankly a weekend closure, where the carriageway level is reduced by, say, 75-100mm over a distance of 100m or so either side of the bridge would be a better solution. Any safety barrier alterations could then be done during the week via lane closures. That would be massively cheaper than demolishing and replacing the bridge.

This lack of headroom problem has happened before on the M1 near Woolley Edge services, on the southbound, at the overbridge just before the exit slip. The headroom over lane 3 became sub-standard due to overlays. Easily fixed by a planer and a new wearing course, or surface course as it's now called I believe.

Edit: Top tip for scheme designers - CHECK THE ****ING HEADROOM!

Wonder which group of cowboys is advising the mega expense and screwing over of non-motorised users who will now have an unreasonable detour to the next crossing?

Easy to see why no-one has a glowing opinion of National Highways outside of road construction circles when stunts like this keep happening.

[swissferry]

Back in 2018 there were VMS saying "M9 BRIDGES CHECK YOUR HEIGHT 4.9 METRES MAX". 4.9m is roughly 16' 1". Not sure which bridge(s) were too low. I'm not aware of anything obvious having been changed. I haven't seen such messages in the last couple of years, though I did see a similar message recently for the A9.

[Vierwielen]

Back in 2018 there were VMS saying "M9 BRIDGES CHECK YOUR HEIGHT 4.9 METRES MAX". 4.9m is roughly 16' 1". Not sure which bridge(s) were too low. I'm not aware of anything obvious having been changed. I haven't seen such messages in the last couple of years, though I did see a similar message recently for the A9.

Maybe the Scots have a different approach to the English.

[Vierwielen]

Here is a picture of the bridge taken in the "A" carriageway.

This bridge had an unfortunate incident many years ago. One dark night a yobo lobbed a brick from the bridge into the path of an on-coming HGV. The brick shattered the windscreen of the HGV and caused the driver to suffer a heart attack. He was able to get his vehicle off the road before dying. The M3 was closed for 18 hours while the police did a finger-tip search. They retrieved the brick that caused the accident, and found some fingerprints on it. The fingerprints were not on their computer. They also took a DNA sample from the fingerprints which they filed away.

A few years later, someone else was hauled into a police station for domestic abuse. A DNA swab was taken and fed into the computer. The DNA showed a relationship of the third degree between the person who lobbed the brick and the person now in the police station. Thuis the two were either great-grandfather and great-grandson or uncle and newphew. It proved to be the latter. I believe that the person who threw the brick is still enjoying a "holiday" at His Majesty's expense.

[Micro The Maniac]

Here is a picture of the bridge taken in the "A" carriageway.

Not that one, Vierwielen, this one, nearer J3

But I remember that incident well... one of several brick-lobbings in quick succession.

[Chris5156]

Here is a picture of the bridge taken in the "A" carriageway.

Not that one, Vierwielen, this one, nearer J3

But I remember that incident well... one of several brick-lobbings in quick succession.

When I saw all the "low headroom" warning signs that appeared recently, I was hoping it was to do with works to fix the missing parts of the gantry sign which have been gone for a couple of years now. No such luck. Maybe they'll fix that while they have the road shut for the bridge works.

[tom66]

Here is a picture of the bridge taken in the "A" carriageway.

This bridge had an unfortunate incident many years ago. One dark night a yobo lobbed a brick from the bridge into the path of an on-coming HGV. The brick shattered the windscreen of the HGV and caused the driver to suffer a heart attack. He was able to get his vehicle off the road before dying. The M3 was closed for 18 hours while the police did a finger-tip search. They retrieved the brick that caused the accident, and found some fingerprints on it. The fingerprints were not on their computer. They also took a DNA sample from the fingerprints which they filed away.

A few years later, someone else was hauled into a police station for domestic abuse. A DNA swab was taken and fed into the computer. The DNA showed a relationship of the third degree between the person who lobbed the brick and the person now in the police station. Thuis the two were either great-grandfather and great-grandson or uncle and newphew. It proved to be the latter. I believe that the person who threw the brick is still enjoying a "holiday" at His Majesty's expense.

Only given manslaughter and six years in 2004, so probably would have been released around 2/3rds the way through or around 2008. Hopefully it was enough time to learn his lesson but does seem like an absurdly short sentence for what was effectively second-degree murder (not that such a crime exists in the UK, but the concept exists in sentencing).

https://www.getsurrey.co.uk/news/local- ... m3-4851112

[RichardA35]

Not seen this reported previously...

A footbridge across the M3 near to junction 3 (Bagshot/Lightwater) is to be demolished this weekend, with a full closure over the weekend.

The bridge is an original feature, having been in place since the M3 opened... but it has suddenly been found to be only 16'4" and not the required 16'6" - but only in the outside lane

https://nationalhighways.co.uk/our-road ... ootbridge/

I'm puzzled why (a) it's only just been found to be under-height, and (b) why demolition is the only option, as opposed to a permanent height limit in lane 4? Especially when a replacement footbridge is not going to be in place before Autumn 2025!

Most likely the carriageway has had one or two overlays since it was originally built, with a subsequent loss of headroom.

If this is the case, then quite frankly a weekend closure, where the carriageway level is reduced by, say, 75-100mm over a distance of 100m or so either side of the bridge would be a better solution. Any safety barrier alterations could then be done during the week via lane closures. That would be massively cheaper than demolishing and replacing the bridge.

This lack of headroom problem has happened before on the M1 near Woolley Edge services, on the southbound, at the overbridge just before the exit slip. The headroom over lane 3 became sub-standard due to overlays. Easily fixed by a planer and a new wearing course, or surface course as it's now called I believe.

Edit: Top tip for scheme designers - CHECK THE ****ING HEADROOM!

I too was surprised by the signs going up and also the seeming surprise by NH.
To me it looks like there has been no overlay of surface course, only an inlay when you look at the pre- and post- SM works where the surface course was progressed one lane at a time and the carriageway looks co-planar with no (or minimal) change in level.
2009 GSV
2015 GSV

With these recent SM works the designer or contractor would have surveyed all structures for integration into the latest incarnation of a 3D model.
To me it is inconceivable that the SM designer, contractor, NH PM and NH maintaining PM were unaware of the issue.
The SM designer would have identified a need for a departure or relaxation for reduced headroom.
The SM contractor would have measured the height of the structure and placed GS6 protection (as seen in the verge in GSV) along the trace and would have had some reassurance that they would be blameless in placing the surface course with substandard headroom.
Another possibility is that the theoretical dynamic deflection of the vehicle against the concrete barrier has impinged into the headroom but I thought there was no vertical deflection taken account of (but I could be wrong).
Whatever the cause, I am unsure whether the story is exactly as told by NH as, if so, it implies some measure of incompetence given they are the PM's of the SM programme and also the maintaining authority.

[SteveA30]

Interesting to see the changed practices within HA/HE/NH. In 2007, footbridges from Camberley to Basingstoke were replaced. Two overnight closures, demolition in July, new bridges in August. Two pleasant midsummer nights out for me on the A30. I'm not complaining about the weekend closure mind......

[Conekicker]

I too was surprised by the signs going up and also the seeming surprise by NH.
To me it looks like there has been no overlay of surface course, only an inlay when you look at the pre- and post- SM works where the surface course was progressed one lane at a time and the carriageway looks co-planar with no (or minimal) change in level.
2009 GSV
2015 GSV

With these recent SM works the designer or contractor would have surveyed all structures for integration into the latest incarnation of a 3D model.
To me it is inconceivable that the SM designer, contractor, NH PM and NH maintaining PM were unaware of the issue.
The SM designer would have identified a need for a departure or relaxation for reduced headroom.
The SM contractor would have measured the height of the structure and placed GS6 protection (as seen in the verge in GSV) along the trace and would have had some reassurance that they would be blameless in placing the surface course with substandard headroom.
Another possibility is that the theoretical dynamic deflection of the vehicle against the concrete barrier has impinged into the headroom but I thought there was no vertical deflection taken account of (but I could be wrong).
Whatever the cause, I am unsure whether the story is exactly as told by NH as, if so, it implies some measure of incompetence given they are the PM's of the SM programme and also the maintaining authority.

You'd like to think everyone did as they were supposed to but perhaps at least one person in the chain didn't do their job. Then everyone else might have assumed, not unreasonably, that with nothing flagged up as a problem, everything was OK.

The other possibility is "scheme limits". If the scheme doesn't involve any works to the bridge it could well have been deemed outside of the scheme limits and thus "Not our problem". For example, on several SM schemes I was peripherally involved in, I pointed out that existing signing on entry and exit slip roads was in need of replacement for various reasons. Every time the response was, "Not in the scheme limits", so the end result was a nice shiny new SM with manky looking slip roads. Spoiling the ship for a ha'porth of tar?

In this case, they weren't altering the carriageway level, so why consider the headroom? If there was already a problem, someone would have been aware before the scheme even started. Or not, as it was in this case.

Remember, the NH PM is effectively "just" an administrator, they tend not to get into the nitty-gritty of the design. I'd be amazed if they were to query something as specific as a headroom if they didn't have a reason to doubt it was dodgy.