Had this by email today!
subject: New Yellow cameras on M5
Please be aware of the following:-
The new yellow cameras being installed between J29 and J31 on the M5
are not traffic cameras but are SPEC average speed cameras. The first
(and subsequent) cameras read your number plate and if you arrive at
the last camera too quickly it is £60 and 3 points. They do not use
film, and you will not see a flash. Prosecutions are electronically
produced.
There are 4 sets of cameras currently installed in each direction.
Although SPECs are used elsewhere in the country these I believe are
the first set to be installed in this region and are likely to catch
a lot of drivers.
I do not know when they will be switched on (they might be already
although there are no warning signs up yet but although warning signs
are in the Home Office guidelines their absence will not constitute a
defence).
The cameras are installed between M5 J29 Exeter (Honiton Road) and M5
J31 (A30 Interchange)