The signs, introduced by authorities in rural St Hilary, in the Vale of Glamorgan, South Wales, to warn drivers about placing too much faith in the directional gadgets, could be brought in across the country if the trial is successful.
According to some media reports, problems arose after foreign drivers found it difficult to understand phrases such as "unsuitable for heavy goods vehicles" but could understand pictorial notices.
The four signs have been introduced around one particular black spot in the village, where the electronic devices direct truck drivers to a shortcut between the main M4 motorway and Cardiff airport. However, the road is far too narrow for many to travel down, causing them to get stuck and sparking major traffic problems.
