M4/M5 smart motorway scheme in operation
Hard shoulder running has become the UK’s default response to increasing motorway capacity as Colin Sowman reports.
Facing a predicted 46% increase in traffic levels by 2040 and the current economic recovery leading to more people travelling to, from and for work leaves the UK government under short- and long-term pressure to increase the capacity on the main motorway network. Particular sections of motorways are already experiencing repeated, sometimes tidal, congestion and both tight Treasury limits and the protracted timescales rule out constructing new major roads – at least in the short term.
According to Paul Unwin, senior project manager with the503 Highways Agency, the UK Government’s default response to increasing motorway capacity quickly and cost-effectively is now to upgrade busy sections to hard shoulder running during peak periods. “By opening the hard shoulder as a running lane, we are effectively increasing capacity by 1,200 vehicles per hour,” he says.
The latest part of the network to use hard shoulder running, which the Highways Agency now prefers to call Smart motorways, is an 11km (seven miles) section around the M4/M5 interchange near the south-west port of Bristol. Costing less than £90 million ($148 million), the scheme was completed in two years and involved erecting 33 new (and refurbishing seven) gantries to carry variable message signs and installing more than 48km (30 miles) of fibre-optic cable. Six emergency refuge areas have been created and 22.5km (14 miles) of carriageway have been resurfaced.
When the UK first introduced the concept of hard shoulder running it was met with much public concern regarding safety.
However, at the opening of the latest smart motorway section near Bristol, Road Minister Robert Goodwill said the move to smart motorway will not only increase peak capacity by 25%, it will actually improve safety levels.
“Ninety per cent of people who stop on the hard shoulder do so for non-emergency reasons and 10% of deaths on the motorway are of people on the hard shoulder; so by putting in refuges we are actually improving the safety.”
Unwin told ITS International that to achieve that same capacity increase around the interchange by building an additional lane and retaining the hard shoulder would take 10 years and cost about £2 billion.
Figures from the UK’s first section of smart motorway, part of the M42 near Birmingham in the West Midlands, show that accident rates more than halved following the implementation of hard shoulder running.
While hard shoulder running is only used in perk periods, there have been no fatalities on the 10.5 mile stretch of motorway since the scheme was opened in 2006.
A lot of lessons learned from the original M42 smart motorway have been incorporated in the design of the latest M4/M5 section. This includes spacing of the gantry signs which are 800m to 1km apart on the latest section (rather than 500 metres on M42) with the loops positioned at the midway point. While the new spacing is more economical, Unwin says it provides ample opportunity for driver information. “It would be difficult to do this over a longer section and there is little need for it but in the smart motorway sections we know the congestion is going to happen every morning and every evening.”
Operationally, when the loop-based MIDAS (motorway incident detection and automatic signalling) system detects an increase in traffic volumes above a threshold value, it automatically reduces the speed limit signs from 112km/h (70mph) to 96km/h (60mph) and then to 80km/h (50mph). However, the decision to open the hard shoulder to running traffic is taken by a control room operator.
“They have a threshold indicator showing the loop data and this turns from green to amber as the traffic builds, and they also use the cameras to see what is happening on the roads. This gives the controller the information needed to decide the optimum time to open the hard shoulder,” says Unwin.
The previous schemes have shown a degree of experience is required in timing the opening of the hard shoulder; too late and congestion will be unavoidable, too early and driver compliance starts to fall.
“It’s about predicting the onset of congestion, rather than waiting for it to happen and this is the whole premise of the system,” says David Grant, divisional director with the Highways Agency. “It’s about predicting when congestion will occur and acting to alleviate it before it happens; it’s about smoothing the traffic flow by restraining motorists from travelling quickly and simply adding to the congestion. “This has brought significant benefits in the West Midlands.”
However, in order to implement this strategy successfully Unwin says a major message has to be conveyed to drivers on all motorways and not just the smart sections: “When motorists see the speed limit has been reduced but don’t see any queues or congestion they feel the system isn’t working properly – but actually it is. We are keeping those vehicles in a ‘bubble’ because there is congestion ahead and slowing them down to prevent them joining the back of the queue.”
Grant adds: “Sometimes drivers will see the speed limits but may never experience the incident or congestion because by giving them that information sooner and changing the speed limits the incident has been cleared or the controller has smoothed the traffic flow and eliminated the congestion.”
The M4 and M5 motorways skirt Bristol to the north and west, leading to a lot of local drivers ‘junction hopping’ remaining on the motorway for only one or two junctions and often passing through the interchange. Many are heading for the Aztec West Business Park which has an exit from the M5 just a short distance from the M4/M5 interchange.
In order to separate local from the long distance travellers, local drivers heading for Aztec West on the westbound M4 will be able to remain on the hard shoulder through the interchange, onto the M5 southbound and all the way to the off ramp. Unwin says this not only leaves two lanes for through traffic it also reduces the speed differentials of merging motorists: “The local motorists won’t be looking to accelerate because they will be exiting the motorway almost immediately.”
Grant highlights another benefit: “The positioning of the off-ramp to Aztec West is not ideal and is often a seed for congestion which quickly backs up onto the interchange. Keeping local and long distance travellers apart and narrowing the speed differential reduces instability and as a result there are far fewer accidents. We have seen this on the M42 where a similar scheme led to a 55% reduction in incidents and subsequent clear-up time that involves.”
Simulator-based research on different groups of drivers was undertaken on the M42 project before the first section was opened in order to confirm the signs would be both clearly visible and easily understood. Yet the transition to smart motorway and hard shoulder running has raised driver education and compliance issues.
Some drivers on the M42 have been anticipating the hard shoulder opening or moving onto the closed hard shoulder before the junction to avoid tailbacks. Other motorists appear reluctant to move back into the main carriageway when the hard shoulder closes.
Grant says: “Hard shoulder misuse is a factor but only with a tiny proportion of motorists. Around 140,000 vehicles a day use that section of road and we have seen about 230 vehicles a month misusing the hard shoulder – some through ignorance; others deliberately.
Any misuse could have significant consequences so the local police have sent letters to the motorists involved. For most motorists it is a case of awareness and education but we do see repeat offenders and the police will now be targeting them for enforcement.”
While compliance may remain an issue with a tiny minority of motorists, the initial safety concerns relating to hard shoulder running have not proved to be a problem in practice – indeed the move has been shown to improve safety. So in a world of growing demand and restricted budgets, any capacity improvement scheme that takes a fifth of the time and one twentieth the cost of road widening must be worth considering.
Variable speed limits
The use of variable speed limits on smart motorway sections has increased driver compliance during periods when the hard shoulder is not being used. David Grant says: “Speed compliance on the smart motorway section of the M42 is more than 95% and remains much better than average throughout the day even when the variable speed limits are not in use. People now recognise that driving sensibly on that section of road actually makes a much better experience with journey times maintained. That becomes self-regulating because when you get a body of vehicles travelling at the correct posted speed, it becomes difficult for others to go faster.”
Safety
In 2006 the M42 in the West Midlands became the first section of motorway in the UK to adopt hard shoulder running during periods of congestion. In the five years prior to the introduction of hard shoulder running there had been eight fatal accidents on that section of motorway. There have still been no fatal accidents on that section either when it is running in traditional configuration or when the hard shoulder is being used as a running lane.
The rate of serious accidents also fell dramatically from 0.7 per month prior to the introduction of hard shoulder running to 0.17 as a managed motorway while the occurrences of serious injuries fell from an average of just over one a month to less than 0.2. Minor accident rates also fell from almost 8.5 per month to 3.72.
At the same time the average traffic speed through the section had increased, as is evidenced by a 22% reduction in journey time which has been accompanied by a 10% fall in emissions.
Facing a predicted 46% increase in traffic levels by 2040 and the current economic recovery leading to more people travelling to, from and for work leaves the UK government under short- and long-term pressure to increase the capacity on the main motorway network. Particular sections of motorways are already experiencing repeated, sometimes tidal, congestion and both tight Treasury limits and the protracted timescales rule out constructing new major roads – at least in the short term.
According to Paul Unwin, senior project manager with the
The latest part of the network to use hard shoulder running, which the Highways Agency now prefers to call Smart motorways, is an 11km (seven miles) section around the M4/M5 interchange near the south-west port of Bristol. Costing less than £90 million ($148 million), the scheme was completed in two years and involved erecting 33 new (and refurbishing seven) gantries to carry variable message signs and installing more than 48km (30 miles) of fibre-optic cable. Six emergency refuge areas have been created and 22.5km (14 miles) of carriageway have been resurfaced.
When the UK first introduced the concept of hard shoulder running it was met with much public concern regarding safety.
However, at the opening of the latest smart motorway section near Bristol, Road Minister Robert Goodwill said the move to smart motorway will not only increase peak capacity by 25%, it will actually improve safety levels.
“Ninety per cent of people who stop on the hard shoulder do so for non-emergency reasons and 10% of deaths on the motorway are of people on the hard shoulder; so by putting in refuges we are actually improving the safety.”
Unwin told ITS International that to achieve that same capacity increase around the interchange by building an additional lane and retaining the hard shoulder would take 10 years and cost about £2 billion.
Figures from the UK’s first section of smart motorway, part of the M42 near Birmingham in the West Midlands, show that accident rates more than halved following the implementation of hard shoulder running.
While hard shoulder running is only used in perk periods, there have been no fatalities on the 10.5 mile stretch of motorway since the scheme was opened in 2006.
A lot of lessons learned from the original M42 smart motorway have been incorporated in the design of the latest M4/M5 section. This includes spacing of the gantry signs which are 800m to 1km apart on the latest section (rather than 500 metres on M42) with the loops positioned at the midway point. While the new spacing is more economical, Unwin says it provides ample opportunity for driver information. “It would be difficult to do this over a longer section and there is little need for it but in the smart motorway sections we know the congestion is going to happen every morning and every evening.”
Operationally, when the loop-based MIDAS (motorway incident detection and automatic signalling) system detects an increase in traffic volumes above a threshold value, it automatically reduces the speed limit signs from 112km/h (70mph) to 96km/h (60mph) and then to 80km/h (50mph). However, the decision to open the hard shoulder to running traffic is taken by a control room operator.
“They have a threshold indicator showing the loop data and this turns from green to amber as the traffic builds, and they also use the cameras to see what is happening on the roads. This gives the controller the information needed to decide the optimum time to open the hard shoulder,” says Unwin.
The previous schemes have shown a degree of experience is required in timing the opening of the hard shoulder; too late and congestion will be unavoidable, too early and driver compliance starts to fall.
“It’s about predicting the onset of congestion, rather than waiting for it to happen and this is the whole premise of the system,” says David Grant, divisional director with the Highways Agency. “It’s about predicting when congestion will occur and acting to alleviate it before it happens; it’s about smoothing the traffic flow by restraining motorists from travelling quickly and simply adding to the congestion. “This has brought significant benefits in the West Midlands.”
However, in order to implement this strategy successfully Unwin says a major message has to be conveyed to drivers on all motorways and not just the smart sections: “When motorists see the speed limit has been reduced but don’t see any queues or congestion they feel the system isn’t working properly – but actually it is. We are keeping those vehicles in a ‘bubble’ because there is congestion ahead and slowing them down to prevent them joining the back of the queue.”
Grant adds: “Sometimes drivers will see the speed limits but may never experience the incident or congestion because by giving them that information sooner and changing the speed limits the incident has been cleared or the controller has smoothed the traffic flow and eliminated the congestion.”
The M4 and M5 motorways skirt Bristol to the north and west, leading to a lot of local drivers ‘junction hopping’ remaining on the motorway for only one or two junctions and often passing through the interchange. Many are heading for the Aztec West Business Park which has an exit from the M5 just a short distance from the M4/M5 interchange.
In order to separate local from the long distance travellers, local drivers heading for Aztec West on the westbound M4 will be able to remain on the hard shoulder through the interchange, onto the M5 southbound and all the way to the off ramp. Unwin says this not only leaves two lanes for through traffic it also reduces the speed differentials of merging motorists: “The local motorists won’t be looking to accelerate because they will be exiting the motorway almost immediately.”
Grant highlights another benefit: “The positioning of the off-ramp to Aztec West is not ideal and is often a seed for congestion which quickly backs up onto the interchange. Keeping local and long distance travellers apart and narrowing the speed differential reduces instability and as a result there are far fewer accidents. We have seen this on the M42 where a similar scheme led to a 55% reduction in incidents and subsequent clear-up time that involves.”
Simulator-based research on different groups of drivers was undertaken on the M42 project before the first section was opened in order to confirm the signs would be both clearly visible and easily understood. Yet the transition to smart motorway and hard shoulder running has raised driver education and compliance issues.
Some drivers on the M42 have been anticipating the hard shoulder opening or moving onto the closed hard shoulder before the junction to avoid tailbacks. Other motorists appear reluctant to move back into the main carriageway when the hard shoulder closes.
Grant says: “Hard shoulder misuse is a factor but only with a tiny proportion of motorists. Around 140,000 vehicles a day use that section of road and we have seen about 230 vehicles a month misusing the hard shoulder – some through ignorance; others deliberately.
Any misuse could have significant consequences so the local police have sent letters to the motorists involved. For most motorists it is a case of awareness and education but we do see repeat offenders and the police will now be targeting them for enforcement.”
While compliance may remain an issue with a tiny minority of motorists, the initial safety concerns relating to hard shoulder running have not proved to be a problem in practice – indeed the move has been shown to improve safety. So in a world of growing demand and restricted budgets, any capacity improvement scheme that takes a fifth of the time and one twentieth the cost of road widening must be worth considering.
Variable speed limits
The use of variable speed limits on smart motorway sections has increased driver compliance during periods when the hard shoulder is not being used. David Grant says: “Speed compliance on the smart motorway section of the M42 is more than 95% and remains much better than average throughout the day even when the variable speed limits are not in use. People now recognise that driving sensibly on that section of road actually makes a much better experience with journey times maintained. That becomes self-regulating because when you get a body of vehicles travelling at the correct posted speed, it becomes difficult for others to go faster.”
Safety
In 2006 the M42 in the West Midlands became the first section of motorway in the UK to adopt hard shoulder running during periods of congestion. In the five years prior to the introduction of hard shoulder running there had been eight fatal accidents on that section of motorway. There have still been no fatal accidents on that section either when it is running in traditional configuration or when the hard shoulder is being used as a running lane.
The rate of serious accidents also fell dramatically from 0.7 per month prior to the introduction of hard shoulder running to 0.17 as a managed motorway while the occurrences of serious injuries fell from an average of just over one a month to less than 0.2. Minor accident rates also fell from almost 8.5 per month to 3.72.
At the same time the average traffic speed through the section had increased, as is evidenced by a 22% reduction in journey time which has been accompanied by a 10% fall in emissions.
