[Madhatter]

The signs anywhere aren't mandatory nless it's in a red circle or it says only. All road works have a lane closed sign on the run up, it's the red triangle with one straight line and one bent.
To drive legally in this country you have to be driving in a lane of your own, if you overtake, you need a clear lane to overtake in, creating a third, or fourth lane is an offence. if you are in a que of traffic and the offside lane is occupied then it's not legal to go between them, there is no lane there. car drivers do it too when overtaking parked cars, your not allowed to squeeze through, your supposed to wait till the opposit side of the road is clear. same with over taking tractors.