What does 2 even mean here?
Broadly, people tend to drive at speeds dictated by the design of the road, by what is 'comfortable', regardless of the speed limit. A speed camera doesn't improve much in that regard.
For example, straight roads with more lanes, wider lanes, etc will generally result in higher speeds. If one truly needs slower traffic speeds for safety in an area, the road can be designed with that in mind, reducing\narrowing lanes, introducing curves, etc (all variable depending on the area). A lot of these measures work well in combination in areas that are seeking to make things more pedestrian friendly.