Smart Motorways Not So Smart

Anyone who drives around the M25 will have noticed that the speed limits set on the overhead gantries appear to bear no relation to the traffic volumes. Speeds are often set at 60, 50 or even 40 for no obvious reason. Other “Smart Motorways” across the country show the same problem, and the result has been a large increase in the number of people fined (or diverted to speed awareness courses) for exceeding the set speed limit. The number of infringements doubled last year according to the Times.

The justification for smart motorways was that they can reduce congestion by smoothing the traffic flows and help to maintain safety. The speed limits are set partly by automated systems that measure the speed of traffic, but apparently they are also set “pre-emptively” by staff where known congestion is likely to occur at busy times. But as traffic volumes can be unpredictable this sometimes results in lower speeds being set than is appropriate – you can frequently see this around the western side of the M25 around London airport and on the eastern side near the Dartford Crossing.

In addition it is known that the odd particularly slow moving vehicle can result in the speed limit being reduced by the automated system. In other words, the “smart” system is not at all intelligent.

However Highways England is now undertaking a comprehensive review of variable speed limits on motorways. Surely it would be better to simply have an advisory system to tell drivers that there was congestion ahead so that they can slow down and avoid the “stop/start” problem that reduces traffic flows?

At present you have a dumb system instructing intelligent humans (which they mostly are) with the result of needlessly slower traffic speeds and drivers being caught out by unexpected changes in the limits or signs they may not have seen or noticed.

Roger Lawson

Twitter: https://twitter.com/Drivers_London

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Proposals to Improve M25/A3 Wisley Junction

Anyone who regularly travels around the western side of the M25 will know that the A3 junction near Wisley has been a congestion hot spot for many years. Traffic joining the M25 from the A3, or leaving it to get on the A3, results in traffic jams. Likewise queues can arise on the A3, partly because the roundabout at the junction contains traffic lights. Highways England have now published their preferred proposals to improve the situation.

There was an informal public consultation which considered several options, but Highways England have revised the one which proposed simply a larger roundabout so as to try to meet environmental concerns (RHS Wisley Gardens are very close by and there are ancient woodlands near the roads). That is the one they are proposing to put to a formal public consultation in early 2018. Prospective completion date might be as late as 2025.

More details are present here: https://highwaysengland.citizenspace.com/he/m25-junction-10-a3-wisley-interchange-improvement/

Comment: This junction is well overdue for improvement so the reaction of most motorists is likely to be that the sooner this is implemented, the better. The proposed solution does look like a reasonable compromise although the details of the traffic modelling would have been helpful. Perhaps we will see that in due course. Will the suggested design actually cope with the likely additional traffic flows around the M25, particularly if Heathrow airport is expanded? The proposed solution may provide only temporary relief and there will be considerable disruption while it is constructed.

Roger Lawson

Twitter: https://twitter.com/Drivers_London

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