Tubes hanging from bridges

Bongedone

I am just curious. Does anybody know why they hang plastic tubes off bridges at roadworks? Specifically on the M4 near reading.

Thanks

wallbash

Guessing its to warn high sided lorries of lower bridges to come.

Bongedone

That's what a collegue said but I was not sure I believed him.

the_big_fact_hunt

it is also common for chains to be hung from beams before bridges, they are simple warning devices for high vehicles as they attract more attention than signs, how can you miss a chain dragging along your roof?

real1314

More likely to be for some of the plant equipment - e.g caterpillar tracked diggers with front arms that can reach higher than the roof of any lorry. The obstacle makes sure the operator lowers the arm when going under bridges.

All the bridges on motorways can cope with all the legal lorries, and you wouldn't have a taller lorry in roadworks - it woudn't make sense.

Dr.Shoe_2

Yes, it is for heavy plant.

goldspanners

or as happened near me last year a tipper lorry that had been emtpying his load in the road woks area forgot to bring the tipping body back down again and took out a bridge.

Simon11

They're there because there's a heigh limit to be inforced!

The bridges may be fine, but there's are other cables ect that cross over later on.

Young_Pretender

They also work on bridges in dips, because it may be enirely possible to drive the front end of a high vehicle through the bridge, but as it climbs up the other side of the dip, it lifts the middle of the vehicle into the bridge. The tubes/chains show the driver the max height of a long vehicle that can actually pass safely through the bridge in this circumstance.

verybigchris

goldspanners wrote: »

or as happened near me last year a tipper lorry that had been emtpying his load in the road woks area forgot to bring the tipping body back down again and took out a bridge.

It's an easy mistake to make: http://www.youtube.com/watch?v=28rKliMFmTI

:rotfl::rotfl::rotfl: