Can I make two suggestions?

Back in the UK, on the country roads and in Scotland the roads are often only one vehicle wide, with passing places ever so often - this makes the cost of paving significantly cheaper. To save on costs how about just concentrating on a single track, where most needed, properly built with a hard core base and culverts and, given people will have to give way/watch out for on-coming traffic, it would probably force people to take it slower!

My other suggestion is to ask the mayor if he would, say, double, the charge for the bridge crossing so that the funds can be used for maintenance of the road north, combined with the cash from owners, it might make a real fund raising difference.