Official figures show smart motorways like the one to be introduced on the M1 in Northamptonshire are more likely to cause accidents.
Highways England's £373million project to turn a 33-mile stretch from junction 13 at Milton Keynes to junction 16 for Northampton and Daventry into a four-lane carriageway with no hard shoulder is due to be completed in March 2022.
BBC Panorama will tonight reveal that 38 people have died on Britain’s 200 miles of smart motorways in the last five years, compared to 90 a year over the whole 2,300-mile network.
And the number of near-misses on one section of the M25 rose from 72 in five years before it was converted into a smart motorway in 2014, to 1,485 in the five years after -- a 20-fold increase.
A "near miss" is an incident with "the potential to cause injury or ill health".
Transport Secretary Grant Shapps told BBC Panorama smart motorways are too confusing for drivers.
He said: "We absolutely have to have these as safe or safer than regular motorways or we shouldn't have them at all."
Smart motorways were introduced to improve the traffic-flow at busy times by using the hard shoulder as an extra lane and relying on overhead signs to warn traffic of hazards ahead.
One section of the M1 between Junction 10 for Luton Airport and 13 was converted in 2012. Critics point to the dangers of cars breaking down and being stranded in lanes of speeding traffic with no hard shoulder for safety.
The Milton Keynes-Northampton’s stretch is among a further 300 miles due to be converted to smart motorway by 2025.
Watch BBC Panorama, ‘Britain’s Killer Motorways?’ on BBC One at 8.30pm tonight.