Smart motorways are still a relatively new concept – the first pilot in the UK took place in 2006 – but they are already an important part of the UK Government’s transport strategy. The most visible aspect of these schemes is making the hard shoulder available for use by traffic. However, smart motorways also use dynamic speed limits and other alerts to keep traffic flowing as smoothly as possible and reduce journey times.
On the face of it this makes considerable sense. Highways England estimates that congestion on the motorway and major road network in England costs an estimated £2 billion every year. As such, smart motorways – using a combination of technologies to increase the capacity and efficiency of the UK’s major road network – are an intelligent solution to tackling this economic burden, at far less cost than traditional road widening schemes.
Smart motorways now account for 200 miles of the UK’s motorway network – a small proportion of the total – but where they are in place, analysis has shown that capacity on the busiest motorways has increased by up to a third. Studies on the smart sections of the M25 have shown that the schemes have supported an additional 11,000 journeys a day.
However, a recent report published by the Department for Transport has painted a slightly more mixed view of the success of smart motorway schemes in the last five years. The data revealed that 38 deaths occurred on smart motorways over the last five years. Moreover, data for 2015-18 (inclusive) highlighted that while smart motorways carried 10.7% of motorway traffic they accounted for, on average, 11.4% of the serious casualties.
Some of these incidents are linked to issues with some of the technology infrastructure that the detail of the report highlights. For example, the camera-based car detection system – used to spot vehicles that are broken down or encountering issues and rapidly send out rescue teams – still takes an average of 17 minutes to spot a vehicle in trouble, and a further 17 minutes for a rescue team to arrive on the scene. Clearly this is exposing drivers to unwanted risk.
As a result of this data, Transport Secretary Grant Shapps has made clear his intentions to tackle these issues. Looking at the data it is clear that the starting point for these solutions needs to be the fundamental technology used in smart motorway deployments.
The limitations of point sensors
The problem with the technical implementation of smart motorways is the reliance on point sensors – in the form of cameras and induction loops in the roadway.
However, point sensors can never deliver full visibility of the entire motorway. Even in a best case scenario you may have loops or cameras every 400 metres. While this gives you good coverage, it absolutely does not give you true continuous monitoring – and these gaps in coverage are where the delays and errors creep in, that increase the risks to drivers.
And where sensors fail – as is common, particularly with induction loops – then the gaps obviously increase. Unfortunately, installing sensors at more regular intervals is very costly – and so there will always be compromises in the coverage point sensors can provide.
Changing the economics of smart motorways
Of course, Distributed Acoustic Sensor (DAS) technology can provide an answer to these challenges. With a fibre alongside a motorway, DAS can provide full continuous monitoring of the entire motorway – providing additional detecting capabilities to spot disruptions in the flow of traffic and changing behaviour in the vehicles.
In this way DAS not only closes the gaps in the sensor infrastructure, increasing the efficacy and accuracy of identifying incidents, but also boosts the speed of response by detecting incidents anywhere on the motoryway in real-time. This is crucial to minimising the potential disruption to keep traffic flowing even more smoothly.
As well as enhancing the core operation of a smart motorway, DAS can also introduce additional benefits – for example detecting potholes in the signatures of the vehicles passing over it, or even providing a rapid alarm system for incidents such as wayward animals entering the roadway or items falling off heavy goods vehicles.
More importantly, DAS fundamentally alters the economics of smart motorways. Because it can make use of fibre that is already installed, DAS makes it commercially viable to extend smart motorway systems, not just to more of the motorway network, but also to the A and B road networks. In this way DAS could truly enable a network of smart highways, not just smart motorways.
We are only just beginning to explore the full potential of DAS to significantly improve the safety and efficiency of our road networks – with several trials currently underway.
But there is no doubt that the technology will be a powerful tool in the effort to eliminate congestion and keep the country moving safely.
Read our technical explainer to find out more about the continuous monitoring enabled by DAS.