The national speed limit of 70mph is to remain on 'smart' motorway stretches of the M1 and M3, despite the Highways Agency consulting on plans to reduce the limit to 60mph.
The 60mph plans were designed to reduce impact on local air quality.
The Highways Agency will continue to use the necessary legal powers to enable them to vary the speed limit from the routine 70mph at certain times.
Transport Secretary Patrick McLoughlin said:"Let me be absolutely clear, I want all motorways to run at 70mph. While it sometimes makes sense to use variable limits to keep people moving, blanket reductions are not acceptable.
"Smart motorways are an effective and cost efficient way of increasing space on our roads, cutting jams and speeding up journey times and I am pleased to announce the start of work on these schemes."
Parts of the M25 are already operating as a 'smart' motorway.
The M1 scheme starts operation from autumn 2015, and the M3 scheme opens to traffic in 2016.