Failing traffic lights that have been causing “horrendous” traffic were damaged during recent resurfacing work, it has emerged.

The lights on the A41 roundabout at junction 20 of the M25, near Kings Langley, have been having phasing issues, Hertfordshire County Council (HCC) has confirmed.

Engineers have been working to fix sensors under the road that normally adjust traffic light timings to traffic levels – but the problem will not be totally fixed until later this month.

A county council spokesperson said: “The majority of sensors are now working, but a final set will need to be replaced while the A41 is shut for resurfacing next weekend.

“We’d like to thank residents for bearing with us while we fix this problem.”

The final works will take place on March 19, and it is expected the lights will be back to normal the following day.

It comes after several people described the traffic as “horrendous,” “dreadful” and “awful” on social media.

One person said only four cars were let through before the lights turned red.