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.
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This year's half marathon is well underway. Runners are already making their way through Cardiff Bay.
Conservatives begin their annual conference looking forward to the Assembly election campaign with UK election victory behind them
Thousands of people are taking to the roads of Cardiff to take part in the Cardiff Half Marathon 2015 today.