All vehicles that are restricted to 60 mph (e.g. Trucks, lorries, campervans etc.) are only restricted to the left hand lane on all motorways, A roads and dual carriageways, with the exception of extreme circumstances (e.g. accidents etc.) and are therefore not permitted to overtake unless the road  behind is absolutely free from any traffic.  This would reduce the amount of traffic and uneccasary congestion but more importantly prevent accidents.