ONLY around one in five drivers obeyed 20mph speed limits in two areas of Gwent during trials of the Welsh Government’s new traffic laws.

Parts of Abergavenny and Severnside were picked for pilot schemes to test out ministers’ plans to cut the default speed limit in Wales from 30mph to 20mph.

The Senedd passed the law last summer, and in six months' time the change will come into force.

The Welsh Government believes the new rules will bring “a number of benefits including a reduction in road collisions and serious injury, more people walking and cycling and improvements to health and wellbeing”.

But it has proved controversial. Nearly 50,000 people signed an online petition saying 20mph limits were “causing chaos” and “doing nothing to reduce emissions”, and drivers in the two Monmouthshire pilot areas also voiced their frustrations over the lower speeds.

The Welsh Government said new data showed “on average, motorists are already driving slower in the first phase areas with an average speed reduction of 3mph recorded across all eight communities” where 20mph limits were trialled.

In some cases the percentage of drivers obeying the new speed limit rose significantly, indicating “substantial behaviour change”.

“This latest data is already showing the benefits we can expect to see across Wales thanks to the bold move we are taking to lower the default speed limits later this year,” said climate change minister Julie James.

“Decisions like this can be unpopular and we know that change is never easy, however, evidence from around the world is clear – reducing speed limits save lives.”

But the data, published by Transport for Wales, also shows the two pilot areas in Monmouthshire had the lowest levels of compliance.

In Abergavenny, the number of drivers complying with the 20mph limit after the trial was just 23 per cent.

On Severnside, only 18 per cent of drivers were obeying the 20mph limit at the end of the pilot scheme.

This was the lowest of any of the eight trial areas around Wales.

The study also looked at whether the 20mph limits made journey times slower.

Results showed “mean journey times…are minimal and generally not more than one minute” in most of the trial areas.

The exception, however, was “the 8.9km route along the B4245 through the Severnside area, where mean journey times increased by up to three minutes”.

Which roads will become 20mph in Wales?

From September 17, all “restricted roads” – typically residential roads where there are streetlights – will automatically be designated 20mph roads.

Councils will be given powers to retain 30mph speed limits on roads where there the higher speed is safe.

Responsibility for enforcing the speed limit will lie with the police and the GoSafe speed camera agency, as it is currently.