A smart motorway speed limit reduced as I went past the camera. Will I be fined for speeding?

I was travelling down the M1 on at 70MPH and, as I reached a gantry, the speed limit signs flashed up 50MPH. I started to brake, but on the other side of the gantry was a speed camera, which promptly flashed me. I was doing about 60/65mph as there was a car behind me and I couldn't brake hard. Can they fine me for this? If they do, do I have any grounds for challenging the ticket?

Asked on 10 November 2020 by Alex Smith

Answered by Georgia Petrie
I believe that when a speed limit changes on a smart motorway, drivers have a one-minute grace period before speed cameras will flash them. That means the cameras don't begin to enforce the new speed limit until one minute after it has changed. You shouldn't be fined, but if you are, I would bring up the fact that it had only just changed and you couldn't safely brake to 50mph.
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