These Regulations amend Schedule 6 to the Road Traffic Regulation Act 1984 which sets speed limits in respect of particular classes of vehicle. The speed limit for a heavy goods vehicle falling within class 5(2)(b) in Part I of that Schedule is 40mph, except where the vehicle is being driven on a motorway or dual carriageway. These Regulations increase the speed limit for such a vehicle to 50mph when it is being driven on a single carriageway stretch of the M9/A9 Trunk Road specified in the Schedule to the Regulations. The relevant stretches all lie between Perth and Inverness.