What Are Smart Motorways and How Do They Work?
It seems like there’s a smart version of everything these days: smart phones, smart televisions, smart kettles – you name it. While it’s fairly easy to see how the items just listed could be termed ‘smart’, it’s not quite as simple to conceive of a smart motorway.
Well, as it turns out, the idea behind them isn’t too complex: sections of motorway that use a combination of variable speed limits and hard shoulder usage at busy times to increase road capacity and traffic flow.
What am I likely to see on a smart motorway?
Control signals: There tends to be two types of control signal which you are likely to encounter on a smart motorway. 1) small signals mounted over individual traffic lanes or the hard shoulder, and 2) larger overhead signals which can display longer, more complex messages, mounted over the hard shoulder or on the verge. Normally, these signals will communicate which lanes are open or closed, and what the current speed limit is.
Variable speed limits: Certainly not a new concept, variable speed limits have been in place on the M25 since the mid 90s. The thinking behind them is that slower vehicles travel more closely together which, in turn, allows other vehicles to make better use of the available road space.
Hard shoulder usage: No longer merely reserved for emergency stops and breakdowns, the hard shoulder can be opened up on smart motorways when the road is particularly busy. This allows another lane of traffic and an instant boost in road capacity to help relieve congestion.
While hard shoulder running, in its early stages, was only open to traffic between junctions to be used an extended exit lane, it’s now used through junctions, too, if necessary. This is because an increase in control signals and the installation of rotating panels on fixed blue direction signs has made communicating to road users a great deal easier.
How do smart motorways work?
Smart motorways are all about keeping traffic moving. So, with this project in mind, it’s essential that the speed and volume of traffic in each and every lane is constantly monitored. But how are they doing this?
- Inductive loops embedded in each lane at regular intervals count the number of vehicles passing along each lane.
- A system of CCTV cameras along the length of the road identifies vehicles in traffic lanes and estimates their speed. From here, the cameras can then give an accurate measure of how quickly each individual lane is moving.
- The loops and cameras feed their data into a central computer system that keeps track of how many vehicles are on the motorway and where they are. When traffic becomes heavy and flow starts to break down, the system will automatically adjust speed limits in an effort to keep it moving.
- Not everything is automated, however: the CCTV cameras and the actions of the central computer system are monitored by the Highways Agency in a control centre. They can choose to intervene or override the automatic system. They can also communicate with Highways Agency officers and direct them towards incidents.
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