Air pollution speed limits that force motorists to drive at 60mph should end, campaigners have said, after it emerged they have lasted twice as long as originally proposed without producing evidence they work.
Drivers on stretches of the M1, the M6, the M5 and the M602 have been limited to a top speed of 60mph in a bid to ascertain if driving more slowly helps reduce emissions.
But the restrictions, which were only supposed to last between 12 and 15 months, have now been running for more than two years, despite no evidence to show they are effective.
There are even questions over whether the increased congestion caused by the new speed limit may have actually increased pollution.
Motoring groups and a former roads minister are among those now calling on National Highways to come clean with the data or end the trials.
Testing stuff is just great. But the aim is actually yo test stiff. Which means doing it, measuring it, then publishing.