No more smart motorways without hard shoulders will be able to open without additional safety measures in place, the government has said.
It said any new "all lane running" roads would need radar technology installed first to detect stopped cars.
Smart motorways use technology and other measures to cut congestion, such as opening the hard shoulder.
But there are fears about their safety after fatal accidents involving stationary cars being hit from behind.
In a written statement to Parliament, Transport Secretary Grant Shapps said that for every hundred million miles driven there were fewer deaths on all-lane motorways than conventional ones.
But he added: "We are determined to do all we can to help drivers feel safer and be safer on our roads - all our roads."
He said Highways England would now accelerate the introduction of a number of safety measures set out last year.
"Most significantly, radar-based stopped vehicle detection technology will now be installed on all operational all lane running (ALR) motorways by September 2022, six months earlier than planned," he said.
"Highways England has also made a commitment that no ALR motorways will open without radar technology to spot stopped vehicles, enable lanes to be closed where necessary and get help to drivers quickly."
Other measures include upgrading cameras so motorists ignoring closed lanes indicated by red X signs can be caught and prosecuted, and putting more signs up about distances to emergency refuge areas.
The RAC's head of roads policy, Nicholas Lyes, said the motoring organisation was "concerned that drivers will still need to wait up to 18 months before all cameras are enforcing red X lane closed signs".
He said: "Enforcement is vital in getting all drivers to obey these signs as anyone who disregards them is at a much greater risk of being in collision with a stranded vehicle."
Smart motorways, which use technology to maintain the flow of traffic and give information on overhead displays, have existed in England since 2002.
The "all lane running" versions - which involves opening the hard shoulder permanently to drivers - began in 2014.
But a coroner in Sheffield found in January that such roads "present an ongoing risk of future deaths" after two people were killed when a lorry ploughed into their vehicles while they were stationary on the M1 in South Yorkshire.
Claire Mercer, whose husband Jason Mercer died in the accident in June 2019, and who now campaigns against smart motorways, said: "It's all compromises. Nothing is new. Nothing short of giving back the hard shoulder in every single instance will be acceptable."
She said she was sitting in a coffee shop with her husband Jason just before he was killed.
"We were sat chatting. At 8 o'clock he got up to leave, kissed me goodbye, told me he loved me, and apparently he was dead by 8:15," she said.
Her husband and another motorist, Alexandru Murgeanu, had stopped after a minor collision.
She said over the past few months support for her campaign had grown exponentially.
"I just don't understand why they [the government] are digging in against accepting public opinion... People are starting to get really angry about being ignored."
In 2019, 15 people were killed on "all lane running" and "dynamic hard shoulder" motorways. This is four more deaths than in 2018.
The number of people being killed on motorways without hard shoulders increased each year from 2015 to 2019, and totalled 39 deaths.
By contrast, on so-called "controlled motorways" - a type of smart motorway which have variable speed limits and a hard shoulder - there were 24 deaths in that period.
On conventional motorways, which cover more of the UK than smart motorways, there were 368 fatalities from 2015 to 2019.
The Highways England report found that crashes between moving and stationary vehicles were more likely on such motorways.
But collisions between two or more moving vehicles - which is how more people die - were less likely due to speed regulation.
The Commons' Transport Select Committee has launched an inquiry into smart motorways, with chairman and Tory MP Huw Merriman warning there are "genuine worries" about the roads.
And the AA and RAC have raised concerns that vehicles that break down on sections of road with no hard shoulder face greater dangers than before.
Reacting to the Department for Transport's update, AA president Edmund King said: "It is encouraging that progress has been made on our demands to make 'smart' motorways safer. The objective should be to create the safest roads we can.
"The number one improvement advocated by the AA and our members is to increase the number of emergency refuge areas (ERAs) and retrofit them to older schemes to ensure they are placed at approximately 0.75 miles apart.
"More ERAs, together with improving the accuracy of stopped vehicle detection radar, should be the urgent priorities."
There are plans for about 800 miles of smart motorway in the UK by 2025 - up from just under 500 miles currently.
At the moment parts of the smart motorway network are not monitored by radar technology, but by human observation from watch centres.
It's the nightmare scenario. Breaking down on a motorway, without a hard shoulder to take refuge on, and with cars and lorries whizzing past inches away.
The government says smart motorways are safer than conventional ones. And it points out that hard shoulders themselves are far from safe. People get killed waiting there, too.
Many motorists will find all this hard to accept, especially when they see other drivers ignoring speed limits or lane closures when incidents occur.
But the government needs to convince them. It's cheaper to have smart motorways than bigger roads.
That's why it says it's going all out to improve safety on roads it claims are already very safe. It wants to reassure people.
The question is, will critics be persuaded?