Enforcement tolerances set by police are often incorrect and result in even lower tolerances. Insurance rates have been falling in the United States despite increased speed limits starting December 1996. This graph shows that total fatalities in both BC and Canada have been cut almost in half since the late 1970's. A poor economy is well known to reduce crashes. Note the big drops in the above graph during the recession of the early 1980's.
Few crashes are the result of one factor.
In both cases, photo radar is of no value in prevention or punishment. Despite shoddy media reporting, these studies imply , but do not show a correlation between tickets and at-fault crashes. Our position on automated traffic enforcement. 17 pages which discuss various related issues, many with footnoted research. 35, no. 3, August 1968.