Speeding to a ticket

In an earlier post I mentioned that I haven't received a speeding ticket in over eleven years.  It's partly because I'm a careful driver, but luck helped—I've been given a warning or two.  But instead of a system of warnings and tickets, where so much is left to the cop's whim, why don't they use a more objective system of total miles per hour over the speed limit?  Every time you're pulled over, your m.p.h. over the limit is added to your total, and if your total is still under some number, say 25, you just get a "warning", but if it goes over, then you pay a standard fine for every 25 m.p.h. over the limit.  Wouldn't that work better?