It won't take 11 mins - more like 5 mins.

There are grass banks either side of the roads all the way to the NEC, although you will need to look where you are stepping with the amount of ducks there are around.

Anyhow, with regard to the roads ... if it's a big convention on, walk in the road - you will end up walking faster than the traffic.
If not, walk in the road anyway.