They're all over the place in N.VA but I still see people running lights daily. Pretty much at every intersecion :-/
No they are not all over the place in N.VA
The only red light cameras that I know of are on 28 south of Braddock Road, on 7100 at Pope's Head Road, on 50 at a street whose name I cannot recall right now, and in Alexandria in front of Landmark Mall.
Those cameras you may see on TOP of the lights are not red light cameras. Those are traffic detection cameras and replace the failure-prone loop detector so that the light won't stay green for cars that aren't there or fail to give a green to cars that are.