From my observations a major source of traffic clustering on 2 lane UK A and M roads is lorries overtaking each other. This seems to happen because some lorries

From my observations a major source of traffic clustering on 2 lane UK A and M roads is lorries overtaking each other. This seems to happen because some lorries drive at 50 mph and others at 60 mph. If all lorries were to drive at precisely the same speed they would rarely have cause to leave the slow lane and clustering of cars would be reduced.