Speed averaging cameras on bridges

[Merlin]

I've been pondering the speed averaging cameras in use around the Cape Town CBD; specifically the route from the N2 through to Rhodes Drive, although to the best of my knowledge, they all suffer from the same flaw: These cameras are mounted to footbridges at either end of the trapping zone.

I recall a big fuss several years ago, relating to trapping from bridges, as they were deemed unstable, due to their designs allowing for slight movement, to tolerate vibrations, tremors, etc..

Surely that invalidates all of these averaging fines too?

I'd love to hear your input on this.

 

[hawker]

For average speed measurements - not an issue surely??

 

[ScottulusMaximus]

Unless the bridge swaying somehow alters gravity and changes the clock on the camera I don't think it's something you should concern yourself with.

 

[Merlin]

Hahaha!

I ask because I'm not an expert on these things. It just seems to me that there could be place for a calibration error, with movement between the cameras and their sensors, especially as these locations are in high wind areas.

 

[supersunbird]

Surely that invalidates all of these averaging fines too?

Why surely? It doesn't work the same as a instant speed capture where sway of bridge can influence the instant speed measurement.

This system does not measure your speed on entry or exit of the zone at all.

 

[ScottulusMaximus]

Hahaha!

I ask because I'm not an expert on these things. It just seems to me that there could be place for a calibration error, with movement between the cameras and their sensors, especially as these locations are in high wind areas.

The average speed cameras work differently to normal speed cameras. They just take a pic of your number plate and then compare the times between the 2, if the 2 camera's clocks are in sync and unless it's vibrating so much the software can't make out the plate it'll be fine.

 

[Merlin]

Thanks for the info', chaps.

Much appreciated.

 

[genetic]

As long as the cameras can see your numberplate, they will work.