Being a smart motorway the hard shoulder is used when the road is busy and the speed limit can be changed from 70mph to 60mph, 50mph or even as low as 40mph. Look out for the overhead variable speed limit changes and STICK to them.
The cameras themselves are almost impossible to spot, as they are small and grey in colour. Some are sited besides the road, while others are in the overhead gantries. Read more about HADECS 3 here.