Police have been out and about today asking motorists to stop and read the registration plate of a vehicle parked 20.5 metres away - the legal standard set by the DVLA.
They are warning that drivers who fail this roadside eyesight test could have their licence revoked instantly.
Many sailed through the spot-check - but for others it was a wake-up call, as our correspondent Carl Edwards reports.
More top news
Local authorities said the move is necessary to "avert the growing number of deaths and increasing harm linked to psychoactive substances".
Sunny and bright spells for most of us this afternoon, feeling pleasantly warm.
North Wales Fire and Rescue Service say incidents of deliberate fires are more common during the school holidays.