Transport for London (TfL) in the UK is planning a two-year trial of average speed cameras in the UK capital.

The cameras record vehicles entering and leaving a road to calculate the average speed, meaning that drivers cannot simply slow down before a camera.

The devices can be used to enforce 20mph zones in the city and potentially replace speed humps.

TfL is planning trials in one street in each of the four London boroughs, which includes Camden, Hackney, Southwark and Waltham Forest, according to

There are already about 100 cameras in the four boroughs and the trial will add to the 780 conventional speed cameras already operating in the city.

TfL plans to introduce average speed cameras across residential areas if the trial is successful.