Average speed cameras on M25 - working or not?

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I always travel at 50mph through the average speed camera zones on the M25. Currently many miles long. Yet half the population speed right past me. Either these people know the cameras do not work, or have no clue to the meaning of the word average. Which is it? Has anyone on here ever received a ticket from these M25 average speed zones?

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I know the gantry camera do not work

It is the average speed cameras I was talking about: Yellow cameras at road traffic works, which goes on for many miles wihout a single worker in sight. Ever.

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Thinking about this some more. I would be suprised if the cameras work at night. The car headlights would be shining towards the cameras. So how would they read the numberplates? Or do they have other methods rather than visable light, such as infa red too?