The Welsh Government report "M4 Corridor around Newport, WelTAG Appraisal Report Stage 1,Issued 24 June 2013 and authored by ARUP shows that shows that traffic levels on the motorway have remained near constant on certain sections over the 7–year period between 2005 and 2012. On some sections they have marginally increased on others they have marginally declined.
The case for a new motorway hinges on the traffic forcasts for 2020 and 2035. If they are right then it is a brilliant investment, if they are wrong and traffic remains static then it is a disaster as the capital could have been better invested. Department of Transport modelling has a chequered history.
The motorway in 2012 was operating at times at it theoretical limit but no mention is made of the variable speed limit system and how that affects capacity.
If changes in lifestyle, especially for the younger generations who are less likely to drive and own a car, continue and deepen then this is maybe a monumental mistake. Personally think there are many things that could be done with the old road and other transport options.
There is still a long way to go with this but Edwina made a firm decision, she must rapidly becoming Jantras favourite politician