A man who died in a road crash on the M1 in Northants on Sunday has been named as Ben Jeacock, 20, of Fletcher Way, Hemel Hempstead, police say.
He was a passenger in a Nissan Almera which hit the central reservation at Rothersthorpe junction.
A 21-year-old car passenger also from Hemel Hempstead, was seriously injured and is being treated in Northampton General Hospital.
The car was travelling south before the crash at junction 15A.
Police believe the crashed vehicle was forced to make a manoeuvre because another driver made a last second decision to leave the motorway.
They have appealed for witnesses who may help them trace that driver.