Rule 151 In slow-moving traffic. You should: reduce the distance between you and the vehicle ahead to maintain traffic flow never get so close to the vehicle in front that you cannot stop safely leave enough space to be able to manoeuvre if the vehicle in front breaks down or an emergency vehicle needs to get past not change lanes to the left to overtake allow access into and from side roads, as blocking these will add to congestion be aware of cyclists and motorcyclists who may be passing on either side