§ Mr. AdleyTo ask the Secretary of State for Transport what assessment he has made of how much the kinetic energy as affecting road surfaces has increased through the raising of speed limits(a) of lorries from 50 to 60 mph and (b) of coaches from 60 to 70 mph.
§ Mr. Peter BottomleyDetailed research into this aspect of road wear is still in progress. The interplay of the different vehicle forces and suspension types is complex, and the effect on the road surface varies according to speed and loading. Current indications are that, at higher speeds, dynamic effects increase the loading on road surfaces. The increases are small and are countered by the improved load spreading properties of most roads at such speeds. The research programme is aimed at determining where the balance between these opposing effects lies.