An 18-point "action plan" to boost smart motorway safety has been launched by Transport Secretary Grant Shapps.

Measures include more places to stop in an emergency and faster roll-out of a radar-based system to detect broken-down vehicles.

Smart motorways involve various methods to manage the flow of traffic, such as converting the hard shoulder into a live running lane.

They are used by Highways England to boost capacity rather than the more costly process of widening roads.

Concerns have been raised about incidents where vehicles stopped in traffic are hit from behind.

Mr Shapps published the findings of an "evidence stocktake" which found that "in most ways" smart motorways are as safe or safer than conventional ones.

The report stated that the risk of a collision between moving vehicles is lower on smart motorways because technology is used to smooth traffic flow.

But the chances of a crash involving a moving vehicle and a stationary vehicle is higher when the hard shoulder is removed.

At least 38 people have died on stretches of smart motorways in the past five years, according to BBC Panorama figures.

Mr Shapps said he has been "greatly concerned" by the number of fatalities.

He went on: "Evidence shows that in most ways smart motorways are as safe as or safer than conventional ones.

"But I am clear that there is more we can do to raise the bar on smart motorway safety."

He claimed the measures he has set out will "help rebuild public confidence in our motorway network and ensure that safety is firmly at the heart of the programme".

Highways England chief executive Jim O'Sullivan said: "We will be taking forward the measures the Secretary of State for Transport has set out, and we will be improving further our information to drivers to help them be safer on all of our roads, including our smart motorway network."

The "action plan" creates a new standard for the spacing of places where vehicles can stop when there is no hard shoulder.

Emergency refuge areas will be installed every three-quarters of a mile where possible in future schemes, down from an existing maximum spacing of one mile.

The use of a radar-based stopped vehicle detection (SVD) system will be rolled out on all smart motorways without a hard should over the next three years.

SVD is specifically designed to detect stationary vehicles "typically within 20 seconds", the report stated.

Dynamic hard shoulder smart motorways - where the hard shoulder is opened up for traffic during busy periods - are to be scrapped amid concerns that they confuse drivers.

AA president Edmund King, a long-time campaigner for smart motorway safety improvements, said the measures announced by Mr Shapps were "a victory for common sense and safety".

But RAC head of roads policy Nicholas Lyes warned "it remains to be seen" whether they go far enough to protect drivers who break down in live lanes.