We have seen with the M6 Toll that drivers can be turned off by the imposition of charges. There is already a toll to get into Wales on the Severn Crossing but no toll to get out.
There is no doubt that the M4 around Newport needs improving. At the moment if there is a bad accident and the road is closed there is no real alternative for drivers.
But if the road is tolled it reduced its economic effectiveness as a lot of people will be put off using it and will simply avoid it.
More top news
Six people have been killed and a seventh is critically injured after a multi-vehicle crash in Birmingham in the early hours of Sunday.
It will be a frosty start for many across the UK with slow-clearing mist and fog across parts of central and southeastern England.
The prime minister says she has proven the "doubters" wrong but still faces opposition from both sides of the Brexit line.