The sign does not record number plates or issue fixed penalty notices

The signs, nicknamed Smiley Sids, show how fast drivers are travelling, smiling at those within the speed limit but frowning at those going over it.

Redcar and Cleveland Council is to expand the number in use from two to eight across the borough.

The borough was among a handful of areas to pilot the signs, which were initially sited near schools.

Data from the signs, which can store more than 50,000 vehicle speeds, will help the council produce a profile of road accident black spots.

'Positive reaction'

The authority's cabinet member for strategic planning, Eric Empson said: "The signs are a friendly reminder to motorists and they don't record number plates and they don't issue fixed penalty notices.

"But what they do is get a positive reaction from motorists.

"We have had several reports of drivers deliberately slowing down after getting that downcast look.

"It may seem a simple idea, but they are very often the best."