The Highways Agency proposed a 60mph speed limit on a 32-mile stretch of the M1 as part of an attempt to ease congestion.
The proposed reduction is part of the "smart motorway" scheme, which would involve the hard shoulder being used as an extra lane.
But the added volume of traffic would risk violating EU restrictions on air pollution.
Lowering limits would reduce amounts of pollution emitted by vehicles at high speed and reduce polluting traffic jams, the Highways Agency believes.
More top news
Approaching Atlantic frontal systems will give a wet and windy night right across the UK with some heavy bursts of rain for everyone.
Police said 375 people attended a rally in Newcastle by the anti-Islam group Pegida, while 2000 people joined a counter-demonstration.
Kelly Osbourne has quit Fashion Police after the E! show came under fire over a comment Giuliana Rancic made about Zendaya's dreadlocks.