The Department for Transport does not routinely collate information about the location of variable speed limits. For principal roads or if the speed limit is varied to 20 mph, local traffic authorities have powers to introduce variable speed limits without consent from the Secretary of State. On the Strategic Road Network, variable speed limits are located among other locations, on:
M25—Junction 10 to Junction 16
M42—Junction J3A to Junction 7
M6—Junction 4 to Junction 5
M42—Junction 7 to Junction 9
M40—Junction 16 to M42 Junction 3A.