JGD - depends on what you mean by less mobile - if you're talking wheelchair and buggy users, the "long" way round is the only option now anyway.
I also genuinely don't see the closure of the underpass as having a negative impact on various local initiatives. The wortks have to be done sometime - it is entirely possible that they will only take 2/3 months but perhaps they want to err on the side of caution and build in a contingency. After all, if they say 2 months without builiding in a contingency, we'd all be on here complaining about the overrun if it didn't complete on time...