I drove back from Wigan to Bristol today and the radio said there was a problem southbound between J4 and J13 on the M6. The traffic info signs about 20 miles north of J14 said time to Birmingham something like 55 minutes. Another gave a time to a junction past the delay and said it was going to be fairly quick.
I wonder where the traffic info system gets its information from. My guess it would be ANPR cameras spotting a car at one location and again at the next and taking the time difference. Add up several of these would give the time for a longish section.
However, this requires a car to actually reach the next ANPR camera and if it does its not held up in the delay. Cars at the front of the queue will go through quickly and the queue will build longer and longer. When you join it at the back, how will it be able to time a car just in front of you reaching the next ANPR camera the other side of the delay.
I would say it is CCTV rather than ANPR cameras. They can monitor the traffic flow and calculate the speed and then relay the information to activate the signs. You can check some of the cameras on the motorways online yourself.
I would guess it's done by continuous analysis of gps locations of a large amount of vehicles travelling on the stretch of road. Big brother is probably watching your sat nav...
As well as the traditional methods that the highways agency use, i.e. loops in the road, I understand that mobile phone companies sell information on traffic information based on the location and speed of movement of the phones. Add to that all the information from the GPS vehicle tracking systems used in fleet vehicles and you'll be getting a good picture of what is happening.
------------- Ollie
2016
Monplaisir - Provence
Camping Les Gorges du Loup
When the road is clear the time indicated is always less than it takes me at my usual 65mph so I guess the data is mostly lifted from the nutters doing 80 in the outside lane.
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Topic: Motorway traffic info source
