I don't think it's just an issue of no trucks on the fast lane. If you drive on 3 or 4 lane roads, such as the M25, there is a visible disturbance to traffic f

I don't think it's just an issue of no trucks on the fast lane. If you drive on 3 or 4 lane roads, such as the M25, there is a visible disturbance to traffic flow even when a truck enters lane 2 on a 4 lane road. This has the effect of pushing all people that drive between 60 and 70mph out of lane 2 and into lane 3, where the average speed is between 70 and 80mph. This, in turn, pushes slower moving traffic into Lane 4 (inside lane) where its not uncommon to see people driving between 80 and 90mph. The overall net result is an awful amount of breaking, lane changing and short spacing between cars.