a road clearance vehicle
a bin lorry
a breakdown vehicle
a vehicle with a 25 mph top speed
a vehicle wider than 2.9 metres
a roadworks vehicle
an escort vehicle
a Revenue and Customs vehicle
a surveying vehicle
a clamping or tow truck vehicle
airport vehicles
any other specially authorised vehicle
Good job it is illegal on private cars ! can you imagine what it would be like on a dark wet evening on a motorway with thousands of drivers with powerful rotating flashing amber lights on the roofs, chaos!