UK speed limits for your 7.5 tonne truck. A roads ( single carriage way ) 50 mph, Dual Carriageway 60 mph Motorways 70 mph. If you get the summons send a photo copy of the tachograph disc or printout showing your speed at the time of the alleged infringement. The tachograph disc is a legal document, - just try arguing with VOSA that it is not. Some of the 'Gatso' cameras are set to catch vehicles over 7.5 tonnes as they are restricted to 40 mph on single carriage ways - the one on the southbound A5 at the A444 junction ( Royal Red Gate ) is a well known example. The problem is, they work on the size ( length ) of vehicle & cannot differentiate between vehicles of different weight classes. They have even flashed cars towing caravans. I know they deserve it just for being on the road!!