I followed a large goods vehicle towards a local roundabout this evening. As the truck entered the roundabout I noticed a sign that had lit up on his approach:
'Your vehicle is overheight for the next low bridge - turn round here' The sign went off as I approached, so I assume it must me equipped with a sensor that can measure the height of vehicles.
I though this was a very good idea, as it gives the vehicle an opportunity to turn before getting trapped in front of the bridge and having to reverse. As it happened said truck was taking the 1st exit from the roundabout anyway.
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There has been one of these on Chertsey Lane Staines on approach to a rail bridge. Sensor on pole activates a sign and a siren. Been there since the 90s. Even so, this bridge has been struck several times in that time period.
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>> I assume it must be equipped with a sensor that can measure the height of vehicles
There would have been an infra-red beam being shone from a grey pole a little way before the sign, to a similar grey pole on the other side of the road. Any overheight vehicle which breaks the beam will trigger the sign.
These signs usually only go up near bridges with a very high strike rate such as on the A52 at Tollerton, or unusually low bridges on major trunk roads, such as the A505 near Hitchin station. Sometimes warning signs from miles back, plus huge bright yellow and black chevrons on the bridge itself, are not enough.
Last edited by: Dave_TD {P} on Wed 21 Apr 10 at 19:18
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I attended one of these incidents some years ago, not in any professional capacity.
I was visiting friends in Nottinghamshire. He had his own company doing bridge inspections for British Rail, mostly to do with the underwater side of things.
He got a call to go and have a look at a bridge in Grantham and I went along for the trip.
On arrival, there was a double deck bus under the bridge with it's roof...er, not under the bridge! No passengers, thank God. GNER expresses were creeping overhead very gingerly.
He looked at the girders and brickwotk, filled in some paperwork and gave the OK for the trains to speed up, saying to me that it would take more than a bit of aluminium to effect a bridge like that ! He liked those callouts, 'easy money', he said!
Ted
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The one I used to like best was on the A30 at Goss Moor in Cornwall. The bridge is 14' 3'' and we had 13' 10'', 14' 3'' and 14' 9'' trailers so it meant that sometimes we could get under but sometimes it meant a lovely detour, when heading west, through Roche and some delightful little lanes for an artic.
The highlight was the farm at a T Junction on Harmony Lane where an old chappie always used to stand leaning on the wall and wave to all of the lorry drivers.
He got to know me ( being female, presume!) and used to positively wave his hand off:)
Sadly, it's now bypassed and his life can't be better for it, though many wouldn't agree.
The infra red beam is not very accurate though, we would often go west under the bridge but the warning would come on on the way back which posed the question, 'I've been under it once with this trailer, so do I ignore it or obey'?
I usually obeyed but the diversion wasn't half so narrow or pretty going East!
Pat
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>>>The one I used to like best was on the A30 at Goss Moor in Cornwall <<<
I wondered if someone would mention 'the old iron bridge' as it was known,
saves me getting my qwerty out you see ;)
Oy've lived in 'the duchy' for 14 years now and it really did used to amaze me to hear on radio cornwall that
'yet another' lorry had clouted said bridge.
When I used to drive TK's through the blackwall tunnel there used to be hanging fings so as you would clout them instead of said tunnel - always seemed a good idea, to me.
Old A30 Goss Moor is mucho bueno for cycling now (Ssshh!)
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So how do we end up with one lorry a week stuck in the blackwall tunnel?
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>>> So how do we end up with one lorry a week stuck in the blackwall tunnel? <<<
I'm going back a bit Z, (decades in fact) but there used to be some dangley bits on the approach to the Nth. bound tunnel entrance used as a height restriction IIRC.
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The dangly bits are still there.
I think the problem arises because the southbound tunnel is higher and a lot assume that the northbound will be the same but those dangly bits will catch on a CB Aerial and set of the warning which triggers the alert.
Pat
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>> The infra red beam is not very accurate though we would often go west under
>> the bridge but the warning would come on on the way back which posed the
>> question 'I've been under it once with this trailer so do I ignore it or
>> obey'?
maybe the ride height had gone up on the trailor as you were travelling empty on the way back, why i ask i once unloaded an artic with a forklift truck and as it was raining the driver parked the rear of the trailor inside the warehouse doors to keep him dry
subequently due to the rise in the suspension as he drove off empty the whole lot wouldnt budge as the back end was trapped in the doorway, i remedied the situation with a pallet of sugar on the tailboard to give him clearance
Last edited by: zookeeper on Thu 22 Apr 10 at 11:48
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That's very true zookeeper, it probably was that.
It's amazing how useful a pallet of sugar can be:)
Pat
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>>
>> subequently due to the rise in the suspension as he drove off empty the
>> whole lot wouldnt budge as the back end was trapped in the doorway i remedied
>> the situation with a pallet of sugar on the tailboard to give him clearance
Saw a camper van similarly "beached at manchester airport. He'd driven onto the multi storey with passengers and baggage. But having seen them off he was to high to get down again.
Last seen recruiting plane spotters to act as ballast - no pallets of sugar were available.
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>>'Your vehicle is overheight for the next low bridge - turn round here'
Much better to turn them away at a roundabout than have to reverse away from the bridge.
Near here there is a brick arch bridge under the railway. Only one narrow lane and a three foot wide footway.
It is signed at 7' 9" and 2.5m and has infra-red type sensors on the approaches but still catches out a lot of vans.
The brickwork in the tunnel is gouged by decades of ill-advised attempts to get too big a van through.
At the local van hire office there are special warnings on the walls and photos of what happens when you don't heed them - and just how much it will cost you!
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A Useful Sign - Cpt. Flack
