just a thought have you considered raising the town area and spanning tracks with bridges?
as to street width it depends as to how much area you have. so do you want space to allow for parked cars at curb as well as a driving lane?
if not you can get cars approximately 1 1/2-1 3/4" wide so use that as a guide.
might be only me but I would think the roadway at lower part of drawing could be omitted only my opinion its your layout to do what pleases you true.
$oo
