British drivers are being warned of "secret" speed traps being set up around the country, which could see them hit with hefty fines and penalties.
Experts are calling on motorists to slow down and take notice of speed limit signs as councils around the UK introduce more 20mph speed limits.
While drivers have been used to 20mph speed limits on certain roads for years, local authorities are introducing them at a greater rate.
Wales became the first country in the UK to make all restricted and residential roads 20mph in the interests of road safety.
While the Government pushed ahead with the scheme to reduce the number of injuries and deaths on roads, backlash to the scheme was widespread.
It prompted the largest petition in Senedd history with 469,571 signatures, beating out other petitions, including easing lockdown restrictions and boosting NSH funding.
While it has since been rolled back, with local authorities able to adjust limits in areas that require a higher speed, road safety benefits have been measured.
The latest data from Transport for Wales shows that vehicle speeds on 20mph main roads have fallen by an average of 3.8mph.
Drivers could face hefty fines when travelling in new areas, especially if there are new 20mph signs
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It found that average journey times increased in 57 of 60 test cases, although most of these were by no more than two minutes.
There has also been a drop in average speeds, contributing to an expected lower risk of collisions and injuries.
Separate data shows that in areas where 20mph limits have been introduced, the number of penalty charge notices has also increased.
Drivers can be slapped with a £100 fine and three penalty points on their licences if they go over the 20mph speed limit, even by a few miles per hour.
Average speeds in Wales have fallen since the introduction of blanket 20mph rules
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Experts have warned that this could be especially true for people driving in new areas where they are unfamiliar with the speed limits and any areas that are rife for police activity in dangerous hotspots.
Cherie Carter, director at Indigo Car Hire, said: "Drivers are being caught out by what some are calling secret 20mph speed traps.
"People don't realise the limit has changed until the fine drops through the letterbox, and motorists need to wise up.
"Even one fine could add points, push up your insurance and, if you are already near the limit, it could put you at risk of losing your licence."
A map of 20mph speed limits currently in place in Wales | GOV.WALESShe advised drivers to "take care", especially in built-up areas where there could be new signs, and called for motorists to assume that 20mph is "the new normal in towns and cities".
Ms Carter added that it was better for drivers to arrive a minute later than expected, rather than being slapped with a fine that costs hundreds of pounds in the long run.
Motorists are also encouraged to update their satellite navigation systems and map apps on their phones to ensure they are alerted when driving into a 20mph zone.