Underpasses are notorious for their susceptibility to flooding, even in areas well above sea level where drainage is not normally a problem, as illustrated by this week’s heavy rains further north.
On the coastal plain where the water table is only just below the surface, they are an impossibility.
We have only recently seen flooding of the A27 cured at road level east of the Broadbridge junction (and a little earlier east of the Fishbourne junction).
As I have shown previously, using the right hand lanes of the present bypass for uninterupted ‘through traffic’ (diverted past Portfield junction) and carried over the Bognor, Fishbourne (and probably the Whyke Road) junctions, could cope with all present (and probable future) through traffic at 60mph.
The other lanes can link all other local roads and also provide access to and egress from the bypass, reducing delays at present junctions to offset the time for an extra mile or two and probably requiring no more fuel for the the extra distance than idling the engines at the junctions.
This is probably the cheapest and most effective solution to the problem.
K W Newby, Elm Park, Bosham