keep THE SPECIFIED ROADS
These Regulations implement variable speed limits on a 7-junction stretch of the M25 (junctions 16-23). They require drivers to comply with speed limits displayed on variable speed limit signs (diagram 670), which remain in force until another sign indicates a different limit or a national speed limit sign is passed. The regulations provide technical definitions for speed determination, including a '10-second rule' for sign activation.
Variable speed limits on the M25's busiest section manage genuine externalities — this corridor carries extremely high traffic volumes where unconstrained speeds would cause more accidents, worse congestion, and greater economic costs from delays. Without this legal framework, no dynamic traffic management would be possible, harming both safety and economic productivity on Britain's most critical motorway. The regulation is targeted, geographically specific, and directly addresses demonstrable market failures on shared infrastructure.