M1 hard shoulder work brought forward
Work to convert the hard shoulder on a stretch of the M1 in West Yorkshire into a permanent traffic lane will start in November.
The Highways Agency had initially planned to begin work on the six mile (9.6 km) stretch, between junctions 39 and 42, in 2014.
It said the £120m project would provide "much-needed" extra capacity when completed in September 2015.
The permanent use of the hard shoulder has been described by some as unsafe.
Similar schemes on other motorways, such as on the M62 between junction 25 and 30, see the hard shoulder used only during times of heavy traffic.
Ch Insp Mark Bownass, of West Yorkshire Police, previously said the M1 changes would "put people in danger".
Meg Munn, Labour MP for Sheffield Heeley, said: "It doesn't make sense and it's not safe."
The Highways Agency said more than 113,000 vehicles a day use the section between junctions 39 and 42.
A spokesman said: "We are confident that the all-lane running design will tackle congestion on some of the busiest sections of motorway, while at the same time maintaining or improving safety.
"Existing schemes have not only improved reliability and eased congestion, but have also improved safety. Findings from the M42 pilot scheme showed that accidents more than halved."
In August the speed limit between junctions 39 and 42 was reduced to 50mph so improvements to the central reservation could be carried out. That work is expected to be completed in July 2014.