once again
ive also used lights to control traffic for a building job
the council get involved and its also a pain
you best bet, and how i would do it, use your van as i "block " and put the hazzards on and slowley walk in front of the van whilst cleaning
put a few cones or warning triangles out in front, so cars have plenty of warning
its not ideal, but you wil get the job done without the council involved
