Great Western Coffee Shop

From my walk through Melksham on Sunday - new railings on the river bridge which will help keep pedestrians and vehicles apart. Been going on for a while - the other side now being done.

(http://www.wellho.net/pix/brrailings.jpg)

To my knowledge, no pedestrians have been hurt by vehicles mounting the pavement ... it has been suggested to me the the footways are weak, and the real concern is that a heavy vehicle on the footway could cause the bridge to collapse.

Many bridges of that sort of age would have been widened at some time in the last century, and it was often the case that if a new pedestrian pavement was being added on one or both sides then the underlying arch wouldn’t necessarily need to be as strong as for the vehicle carriageways.  It might be obvious if viewed from underneath? 

They may also be worried about the parapet strength with regard to vehicle impact, the new railings will protect against that as well.

Paul

Not only bridges of that age - this has been done to some of the overbridges on the M4 (built c1969-71), although I think the habit of some who parked on the "pavements" on the bridges to sit and watch the traffic go by did not help.

Its a long time since I was involved in bridge design (about 1980) but IIRC the carriageway is designed to a full traffic load including an abnormal vehicle, but the worst loading case for a footway was a single accidental HGV wheel load of 113 kN (about 11 tons).

Unless the bridge deck had badly deteriorated I am not sure that a parked car would have much effect, but a parked multi axle HGV might as it could have more than one wheel load acting at once.  I suggest that the barrier is most likely to be to keep HGV's off the footway therefore.