That is a truvelo(they do a few different styles) and they do tend to be facing towards the front of the vehicle (though they can either way on narrow roads) and they rely on Peizo strips in the road to do the time/distance measurement (hence they can't be detected by a radar/laser detector). They do flash though it's very subdued mainly due to it being an infra-red flash unit (works then in all light enviroments). It's alll they have in bedfordshire/northhamptonshire... [for legal purposes the next bit is pure fiction
] It's the ONLY camera that's ever flashed me but I was on two wheels at that point in time and yes you can see the flash