Motorway widening

[sarah.t]

When motorways get widened (as in the case of the M25 around junct. 13 at the moment) what happens about bridges - such as where they go over the motorway, or where the motorway becomes a bridge over another road / river. Do you think all these will have to get replaced as well, or will the road narrow down to its current width at these points? I imagine it would be quite irritating to keep merging in and out of lanes to get round these obstacles!

[darth vader]

Bridges have been built with this in mind and have space to create an extra lane. Where this may not be possible (older bridges) then the hard shoulder gets used and there is no hard shoulder for the 50 yards or so. As last resort yes they merge the traffic, but the M25 is (relatively) new so i don't think there would be a problem

[darth vader]

three stars! ta!

[smorodina]

If necessary they build new ones. They've just widened the M2 around Medway from two to four lanes and new bridges were built alongside the old ones, roads rerouted over them and the old ones demolished. Where it crosses the river they had to build a second bridge to carry the new lanes. I know they sometimes take away the hard shoulder, but I don't know of anywhere the road merges just because of a narrow bridge?

[SpyWriter]

I remember huge disruption with bridge alterations when the 2 lane parts of the M5 were widened. On the other hand some roads get altered by adding new ones running parallel to the original. I think parts of the A1 and the M42 were done like that.