If you take the lane on the Menai Bridge with a loaded tourer nothing will be able to get past you and anyway you'll probably be stuck doing 5mph behind some bloke in a 4x4, towing a caravan and trying to negotiate the arches, I've driven over that bridge many times and never faster than about 15mph.
How long to resurface Holyhead Road? Is it just one bloke with a wheelbarrow and a shovel doing the work?
You'd think so. It's signed as lasting from 18/8 to 8/9. It took at least three weeks to resurface Caernarfon Road.
You are right about the bridge traffic; rather than cross the whole bridge at a moderate speed, most drivers get a bit nervous about the first arch, clear it, accelerate, and repeat. Then they have to slow down anyway for the bend or roundabout.