The portable device tracks drivers from 100m away

The new portable speed monitors are designed to encourage drivers to slow down by displaying their speeds on a roadside board.

Twenty-four of them are now in use on roads in the Belfast area.

Similar automatic speed signs are already in use on roads, but the new monitors are the first to be small enough for use in built-up areas.

The new Speed Indicator Display (SIDs) will initially be used in urban areas.

The portable device tracks drivers from a distance of 100m and beams up their speed on a roadside board.

'Careless driving'

PSNI Chief Inspector Mark Purdon said the devices would remind drivers to watch their speed and officers would place them in areas such as schools, shopping centres or built up areas.

"In fact, these displays can be placed almost anywhere that a perceived speeding problem exists," he said.

"It is very important to remind drivers that they must remain within the speed limit. These devices will help to encourage drivers to do so. We are giving motorists every opportunity we can to make them slow down."

The police are also set to launch an operation targeting careless driving which will take place in the coming days in the greater Belfast area.