All-lane smart motorways show boost in average speeds

Data suggests that the removal of a hard shoulder brings a higher miles per hour rate, but concerns over safety remain

Credit: Rui Vieira/PA Wire/PA Images

The government’s favoured type of smart motorway – all-lane running with no hard shoulder – appears to result in higher average speeds than sections of smart motorway that retain a hard shoulder, according to data published by the Department for Transport.

Average road speed data for sections of the M1, M6, M25, M42 and M62 motorways published on 5 March showed all-lane stretches had an average speed of 63mph in 2019, the same as conventional parts of these motorways. ‘Controlled’ smart stretches, which have variable speed limits but retain a permanent hard-shoulder, averaged 58mph and ‘dynamic’ stretches, which have a part-time hard shoulder, averaged 55mph. 

On the M1 and M6, all-lane smart stretches had faster average speeds, of 65mph and 64mph respectively, than the 63mph averages on both motorways’ conventional stretches. All smart motorway stretches use technology to monitor and manage traffic, primarily with variable speed limits. 

Highways England cautioned against comparing different sections of road, given variations in usage, safety performance, speeds, vehicle and journey types and traffic volumes. 

“To assess the impact of a road scheme, rather than comparing it with other roads our usual practice is to compare the same section of road before and after the intervention, taking into account any background trends to give a ‘counterfactual’ view of what would have happened if the scheme had not been built,” said a spokesperson. “For this reason, we do not typically compare average speeds across different motorway design standards.”

Average speed of all-lane smart motorways across England

Number of fatalities on roads in England in 2018, including 86 on motorways, of which 19 were on smart motorways

Proportion of vehicles travelling above 50mph on the all-lane running stretch of the M25 to the north of London

135 miles
Cumulative length of all-lane running motorways across England

The government-owned company, which runs motorways and major A-roads in England, has previously carried out a counterfactual comparison of two stretches of the M25, after converting them standard three-lane motorway with hard shoulder to all-lane running. The evaluations, published in 2017, both found increased average speeds as a result of less congestion. 

For junctions 23 to 27 north of London, the proportion of vehicles travelling at between 51mph and 70mph increased from 65% to more than 85%, with a similar shift on junctions 5 to 7 south of the capital. Comparisons of lane speeds on two days before and after the conversion showed periods of congested slow running greatly reduced by the move to all-lane running on both stretches, as well a narrowing in differences between lane speeds.

Safety concerns
But all-lane running has been criticised on safety grounds, given that drivers experiencing a breakdown have to find an emergency refuge area rather than just get across to the hard shoulder, or risk being stationary in a live traffic lane. The head of the Police Federation John Apter has described them as “death traps”. There were 19 deaths on smart motorways in 2018, out of 86 on all motorways and 1,522 on all roads.  

On 12 March, transport secretary Grant Shapps said that radar-based ‘stopped vehicle detection’ systems which help detect stationary vehicles will be installed on all smart motorway sections within 36 months and that more emergency refuge areas will be added with the aim of having no more than a mile between each one. 

He also said that ‘dynamic’ smart motorway stretches will be converted as they confuse drivers. This followed the department’s announcement of plans for several new stretches of smart motorway in its road investment strategy for 2020-25, including parts of the A1(M), M25, M3, M40/M42 interchange, M56, M6 and M62.

Data released in an evidence stocktake and action plan published by the Department for Transport with Shapps’ announcement provided a mixed picture of all-lane running’s safety, with higher fatal and serious casualty rates than dynamic and controlled stretches measured by vehicle miles travelled but a lower rate of less severe casualties. 

“We are determined to do all we can to make our roads as safe as possible… 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”
Jim O’Sullivan, Highways England

All the smart motorway types had proportionally more serious and slight casualties than conventional motorways, but fewer deaths. A counterfactual comparison of nine stretches of conventional motorway converted to all-lane running found total casualty rates are 18% lower than if they had not been converted, although the number of fatal and serious casualties is 2% higher.

“Every death in any road accident is tragic, and we are determined to do all we can to make our roads as safe as possible,” said Jim O’Sullivan, chief executive of Highways England, in a statement. “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.”


Sam Trendall

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