Odd M42 Gantry Camera Behaviour

[Freypal]

Just been along the motorway and the overhead gantries were on showing 50, 40 then 40 again.

I actually noticed the camera flash someone in the distance and I was doing 40 myself. As I approached the gantry the sign changed from 40mph to the national speed limit sign. As I don't trust them I stayed doing 40mph through it however as i passed through it it flashed as I was at the end of the white line markers. Looking around there was only one other car near me in the fast lane but they can't have been doing more than 45-50mph themselves.

Question is if it had changed to show the NSL sign, how can it flash? There is no way anyone was going anywhere near 70+ through it and I myself was only doing 40... got me worried now!

That series of gantries have been behaving strangely the past week or so In the mornings having these 40 limits on and saying queue caution when the road has been clear...

Edited by Freypal on Tuesday 23 October 17:45

[996Keef]

From what I can make out, Hadecs3 does a flash to calibrate for the new speed limit .

So every time the limit changes , there's a flash from the end of the gantry, rather from the actual cameras on the gantry

Could be bks but I think it's been discussed here before

Also, there is a 10 sec to 1 min delay in between gantry change and speed limit enforcement, to save drivers wellying the brakes

[Freypal]

That's interesting and could explain it, the flash would have been around 5-10s after the overhead sign changed to NSL. Hopefully it is as you say a calibration flash!

I'd heard that about a grace period when the limit decreases to prevent as you say people slamming brakes on and thought it was around a minute.

This was just bizarre though as it was going from a 40 to NSL so should change the trigger instantly.