OK, A confession before I ask the question.
Back in July I drove my little truck down to Barmouth. I was doing another agency a favour as they did not have anyone who was authorised to drive it. My brief was to drive it down, set it up, make myself scarce and then pack up and drive home. I had a wonderful day...must have been the hottest day of the year - took a book, lazed around with a coffee for ages.
Time came to set off for home. I had driven down via the normal route I would have taken but this had involved a 6 mile diversion via a narrow road because of a weight restriction on a bridge that's being upgraded (thanks to the good taxpayers of Surrey), as I was driving out of town I considered driving home another way...as all this was going on I drove my 11'6" high truck under a 10'5" railway bridge....there was a clatter as I did this (clearly) and I stopped straight away (clearly) and phoned in a "bridge-strike" to Network Rail. Checked my truck for damage and found that there was some superficial damage to the roof-top air-con unit. I checked the bridge and found some paint marks on the galvanised steel lining of the bridge. I checked the signs and found them to warn drivers that it was 10'5" - clearly it was more than that given the minimal damage to the bridge and van. Hands up my fault, no excuses etc.
Anyway I am now a very careful trucker and double check widths and heights - driving home tonight I turned onto the new Porthmadog by-pass and noticed that there are to railway bridges (one for the mainline and the other for the WHR/Ffestiniog lines) now these have been built at a height to allow trucks safely underneath but there is no warning as to how high the bridges are...
Two questions arise...
1. How much margin of error do Highway Authorities build into the warning signs, is this random or is there a fixed rate ?
2. Why are these new bridges not signed with appropriate height ? - this route is used to transport big boats on occasion....
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Q1 - I've no idea
Q2 - Trucks operating within their length, width, and height restrictions are restricted in height (16' 4" IIRC) and bridges higher than that don't need to be signed.
It's only when an indivisible load which goes outside these limits is carried that the height of bridges above 16' 4" would be a concern.
Last edited by: Number_Cruncher on Tue 29 Oct 13 at 18:05
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You beat me to it NC;)
Q1 Never rely on ANY margin of error, and never believe what another driver tells you.
If it says 12' then don't even try it if you are over that.
Remember if the sign is enclosed in a red circle it is prohibited even if you do manage to get under it safely!
Pat
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"I drove my little truck"
God knows why but whenever you mention that thing this guy pops into my head...
www.windofkeltia.com/allo/grubertank.jpg
;-)
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>> "I drove my little truck"
>> God knows why but whenever you mention that thing this guy pops into my head...
>> www.windofkeltia.com/allo/grubertank.jpg
Me also, perhaps we're watching too many old repeats?
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Q1 - I've no idea.
Q2 - As NC says. In a previous life about 20 years ago I used to design bridges. IIRC we designed to 5.1m but added extra height to allow for resurfacing and for sag curves.
Some roads were designated special high vehicle routes and the bridges were designed for a few feet more. Although the highway authorities would need to be consulted before these were used.
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If the two bridges are new and on a main road then they must be at least 16'6" clearance across the span if they are unsigned.
As to the tolerance; I was always taught that there is none. Every vehicle over 3.5 tonnes GVW (or above a certain height but i can't remember what)should have a fixed height indicator in the cab, clearly visible to the driver. If you are pulling an articulated trailer then it is up to you to ascertain the maximum height before setting out on your journey and re-set the marker accordingly. Ditto a high load on a flatbed.
It doesn't always do to assume that the cab plate is correct either. I took delivery of a new lorry in April whose marker was set at 12'5"; walking round it, the lorry just LOOKED bigger and the nagging feeling would not go away. Out came the tape measure and sure enough it was 12'6". Now you may think that is either bulldust or phenomenal spatial awareness, I really don't care; in fact it's probably something to do with having spent thirty years driving the damn things and you get a sixth sense of when something is not right.
Either way, had I taken the marker as gospel it could have had very embarrassing and expensive consequences.
As Pat says, if your indicated height is greater than that indicated on the bridge and you prang it, you are in deep carp, specially if it's a railway bridge.
Last edited by: Harleyman on Tue 29 Oct 13 at 19:13
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In fairness the vehicle dimensions are clearly marked on the (redundant) interior mirror - there was no excuse for what I did .....my mind was in neutral and it could have been a damn sight worse
I had a discussion with a very nice Officer from the BTP over the phone - not heard nothing since.
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"Pedant" writes:
It's the minimum headroom you need to watch, not the maximum. :)
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Wasn't he some TV nutter? I'm sure I've seen something on one of the freeview channels about it.
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Early days Channel 4 character....I enjoyed it ! :-)
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An ex double decker bus got its picture in the local papers last week. Bus company said the driver was very experienced.
Me, I say the driver is a prat, perhaps used to single deckers, but the rail bridge in Harpenden is well known for getting bridge strikes as it's a bit low.
Only place I came unstuck with a mast equipped Range Rover (I used to work for BBC Engineering) was a road to a car park that turned out to be height restricted - and the sign was after the road became one way... I checked this out as the only way I could get out was to drive the wrong way down a one way street and had ample opportunity to double check the signs.
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The famous 11'8" bridge. Its has flashing lights to warn you are approaching over height.
They get ignored.
www.youtube.com/watch?v=JsAlzV4qSD8
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The signed height should be the measured height, less 3", then rounded down to the next 3".
So, for example, if the measured height is 15' 2" then knock 3" off which gives 14' 11" then round down to 14' 9".
Source: Traffic Signs Manual, Ch. 2
I have been retired from highway design for 6 years now and am just begining to forget these things. :-)
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Sorry, brain fade, that should be Traffic Signs Manual, Ch. 4
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Arctophile, can you explain why some bridges have a triangular advisory sign and some a round prohibition?
Thanks
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>> Arctophile, can you explain why some bridges have a triangular advisory sign and some a
>> round prohibition?
It's a long while since I last looked at this as most of my work related to roads with new structures which usually provided full height.
From a quick read of the manual it would seem that the triangular warning signs should be used at arched bridges where the main danger is from vehicles striking the sides of the arch. The circular prohibitory sign should be used at non-arched bridges where strikes are likely at any point under the bridge.
I am sure that there must be many, many locations where this regime is not followed.
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>> Arctophile, can you explain why some bridges have a triangular advisory sign and some a
>> round prohibition?
I understand triangular signs are warning and circular are mandatory.
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All the regulations relating to signage and road markings can be found here.
www.gov.uk/government/publications/traffic-signs-manual
Fascinating they are too. How many on here know that the "Migratory Toads Crossing" warning sign can only be displayed between May and September?
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>> Fascinating they are too. How many on here know that the "Migratory Toads Crossing" warning
>> sign can only be displayed between May and September?
yeah - read it.
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>> All the regulations relating to signage and road markings can be found here.
>>
>> www.gov.uk/government/publications/traffic-signs-manual
Strictly speaking the Traffic Signs Manual provides advice on how to apply the regulations.
The regulations themselves are contained in "The Traffic Signs Regulations & General Directions (2002)", known as the the TSRGD. A much weightier tome. They can be found here:-
www.legislation.gov.uk/uksi/2002/3113/contents/made
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I shall commit it to memory.
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>> The signed height should be the measured height, less 3", then rounded down to the
>> next 3".
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Very interesting, thank you for that.
It would explain the variations in loading gauge which perplex many drivers; I had no idea that there was a standard formula for it, having assumed that the more generous tolerances on some bridges was down to other factors such as subsidence or resurfacing.
I should add that by perplexing, I mean that on some bridges one's lorry roof is far closer to the edges than on others, despite the bridges being apparently of the same clearance. So by using your formula, the actual clearance height of your example can vary by up to five inches.
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No idea what the standards are for vehicles, but I'd expect the quoted height to be when unladen and tyres at the fully laden pressure. Bit daft if the sign in the cab says 15 foot clearance needed and it hit a 15 foot 2 inch bridge.
I've seen film of a stuck vehicle getting out after the tyres were let down.
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I've witnessed the after-effects of taking a chance on it. Back in the 80's I used to deliver to an industrial estate outside Brighouse, on the A58 IIRC, which was crossed by a railway bridge further down the road. Was there once and my load took ages to tip so I was there a long while; saw a well-laden artic crawl up the hill, pull in to a neighbouring factory, unload and eventually leave.
A few minutes later, traffic began to back up on the main road, and then the sirens started. Apparently matey had just scraped under going up the hill with a load on, coming back down empty he forgot how close he'd been, hooned down the hill back to the motorway and turned a perfectly good curtainsider trailer into a flatbed. Luckily nobody else was involved and he was unhurt.
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>> Wasn't he some TV nutter? I'm sure I've seen something on one of the freeview
>> channels about it.
>>
youtu.be/cYdpOjletnc
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There-but-for-the-grace-of-God, RP.
That will have been an expensive mistake, I should think. I once drove into a B&Q carpark in a Luton van, without thinking about it, under the bar. It went through without thinking about it... On the way out when my brain was switched on, I cannot have had more than an inch's clearance.
Harleyman, you can in fact have up to six inches (less a thou') clearance.
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Exactly Mapmaker - I was extraordinarily lucky...a smidgin higher and that air-con unit would have been off. It was a fantastic day and this spoilt it a bit. First time on a public beach in the UK I saw topless sunbathing. (earlier in the day).
Funnily enough noticed that the road tunnel where I work has a 3.0m warning which is mandatory...never noticed that today. I love this site where you can learn about stuff like this.
The other hazard with this van is forecourt canopies - I use the local Morrison's which offers 5 meters.
I was scared of this van when I first met it - 11'6" tall and 27 feet long....it really daunted me but based on the "how hard can it be" principle I have learned to love it. Very tight turning circle for such a long thing...
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Tip for you RP, watch the rear overhang behind the axle.
Try and memorise how much there is and think of the tail swing when turning in tight places;)
Pat
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Thanks Pat....It should have a reversing camera....I get some respect from other truckers in it...:-)
I've also learnt the art of momentum....keep going regardless smaller fry will generally give way
Last edited by: R.P. on Wed 30 Oct 13 at 18:25
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Aaaaah, at last we have one who understands why lorry drivers are so bull headed:)
Pat
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>> Tip for you RP, watch the rear overhang behind the axle.
>>
>> Try and memorise how much there is and think of the tail swing when turning
>> in tight places;)
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>> Pat
>>
Too right!
I borrowed the firm's van to do a family removal, and forgot that when turning in our drive, and demolished a rockery with the tail lift.
I'm not familiar with the van, and never normally drive it. It seems so like a car most of the time it's easy to forget.
I remember the first time I drove a Volvo 240 I forgot the long front overhang and side-swiped a friend's gatepost when reversing. I suppose both are the price paid for manoeuvrability, in not having the wheels at the corners.
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I guess if you parked it up in Waitrose you'd only get people asking for your advice on whether to stick with the Chablis or risk the Chenin Blanc.
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Probably - might do that tomorrow - You're showing off wine wise now aren't you
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Bought a book y'know. Up to chapter 3 already. Watch this space...
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>> Harleyman, you can in fact have up to six inches (less a thou') clearance.
Theoretically yes, I'd considered that but assumed that they'd only be dealing with whole inches in practice.
Last edited by: Harleyman on Wed 30 Oct 13 at 22:13
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You did that ?!
Jeez !
Last edited by: Runfer D'Hills on Sun 5 Jan 14 at 11:12
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Must have dislodged the plug...
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I'd get that leaking radiator seen to if I were you.
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33 seconds in and you can see the signage for the bridge (I approached from the other direction)
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Max Headroom... - Number_Cruncher
