The new hi-tech signs include display pictures followed by text information warnings and have been designed to provide motorists with images of road conditions, accidents and speed limits.
Transport minister Kim Howells said: 'Providing motorists with prompt and accurate information about road conditions is essential for the smooth running of the network and making journeys safer and more reliable.
'These innovative signs can be understood at a glance and will assist drivers on their journeys, allowing them to react and adapt to changeable road conditions.'
The signs are automatically triggered to detect slow moving traffic but can also be manually set by the local police. If the trial is successful the signs will be installed across the motorway network.