According to the Police's own statistics less than 5% of all injury accidents are caused by people who have exceeded the posted speed limit. Therefore 95% of all injury accidents are not affected by a speed limit. Bad driving causes the vast majority of accidents. Poor driving skills and inattention are the two major factors, and the latter is adversely affected by having even more signs/speed cameras taking their attention away from the road.
The whole 'speeding' issue has taken the attention away from the REAL cause of accidents, and it's an utter sham that the Government have decided to opt for raising cash rather than saving lives.