True, some highways in the Netherlands already use a system like this.

Worst part is, in a stretch of road with for instance 15 camera's . they won't take the average speed between camera 0 and 14, they'll fine you for the most expensive one.

So:

if you average 100 Km/h from 0-14,

and average 115 Km/h from 0-5,

and average 117 Km/h from 8-9.

You get a fine for the 117 km/h

And, in any case, isn't much different than automated radar + photo tickets that have been implemented in some places in the US.