A permanent 50mph limit along the M4 around Newport has been proposed as an alternative to building a new motorway bypass south of the city.
South East Wales Transport Commission set up to look at an way of improving traffic flow after First Minister Mark Drakeford axed the recommended new road on environmental and cost grounds said the lower permanent limit would be a “fast-track” measures to ease traffic at the Brynglas tunnels.
The current variable limit up to 70mph produces a “ripple effect” of changes in speed which disrupt traffic, it said. The 50mph limit between junctions 24 and 28 would apply all day.
In a progress report, the commission admitted this would mean slower travel times for vehicles at off-peak times.
“It is worth noting the case for 50mph speed control goes beyond congestion alleviation. There are also good arguments from an emissions and road safety perspective – these apply to all parts of the day,” it said.