Average speed cameras are being switched on this week at a “collision hotspot” on the A55 at Denbighshire.
A study in March found 55% of vehicles, 217,642 out of 394,326, driving westbound at Rhuallt Hill exceeded the 70mph limit.
Cameras have been installed at junctions 28, 29 and 30 as part of a trial.
“We’re working towards no speed-related incidents, not more speeding tickets,” said a Traffic Wales spokesman.
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“The intention of this trial is to achieve a reduction in high-speed collisions westbound, thus improving safety, reducing the disruption brought about by such incidents and roadworks required to repair infrastructure.”
Traffic Wales is the Welsh Government’s traffic information service.