Police chief's concerns over smart motorways as four lanes opened on M1 between Northampton and Milton Keynes

National Highways has opened all four lanes to traffic on a 9.4 mile stretch of the M1 between Northampton and Milton Keynes amid more safety concerns over smart motorways.

The agency says 60mph speed limits will stay until technology designed to spot stranded vehicles is fully commissioned later this year.

Yet Northamptonshire Police Chief Constable, Nick Adderley, admits he is “not a fan” of scrapping hard shoulders in favour of an extra live lane.

In July, one man died and four passengers were injured on an existing stretch of smart motorway in Northamptonshire, near junction 17.

Crash investigators believe the victim was standing behind a stalled Mercedes in lane one when it was in collision with a Toyota Previa.

A National Highways spokesman said: “All four lanes on the 9.4-mile stretch between Newport Pagnell Services and junction 15 are now available for use.

“A 60mph speed limit, temporary additional CCTV from the roadworks and a free recovery service will remain in place alongside the new permanent systems while final technology tests are carried out.

“New lanes junction 15 and 16 will also be in use next month.

“Both upgraded sections are expected to be fully open with the national 70mph speed limit restored before the end of the year.”

Extra safety measures have been included following recent reviews and the finished upgrade will feature 46 new emergency areas every 0.9 miles — around 1,400 metres apart — for vehicles to stop in emergencies, eight more than were originally planned.

Stopped Vehicle Detection systems will alert controllers to stranded traffic in live lines, allowing them to close lanes by operating Red X signals.

Mr Adderley said recently: “Having worked on roads policing for many, many years, the dangers of motorways are there for all to see.

“I’m not a fan of smart motorways, really. When you have no dead lane, if you break down you have nowhere to go. You’re running the gauntlet.

“Two things were promised when smart motorways were introduced. One was there would be refuge areas every 700 metres. That hasn’t happened and that’s a risk.

“The second thing was a CCTV system to alert highway patrols when a vehicle is broken down or is in difficulty, not placed where they need to be placed.

“I know the Department of Transport is working on.

“But if they were to ask me, I’d be a happier person if they should revert back to traditional motorways.”

Earlier this year, Thames Valley Police revealed how two officers had to run several miles to a fatal M1 crash on a stretch between MK and Northampton.

PCs Matt Diduca and Colin Riley were stopped by four lanes of stationary traffic and, with no hard shoulder, were forced to abandon their vehicle.

New Prime Minister, Liz Truss, last month admitted another review into smart motorways is needed following a number of deaths.

Ms Truss was asked by a Tory party member ahead of the leadership election whether she would scrap smart motorways.

She responded: “I absolutely think that we need to review them and stop them, if they’re not working, as soon as possible, and all the evidence I have agrees with the point you’re making.”