The_Dark_Side said:unless i'm mistaken haven't the US police been using helichoppers to catch speeders for almost three decades?
This is true - the freeways here are patrolled by aircraft. There's warning signs about them on a lot of roads - the I-5 heading south from LA to San Diego and the I-15 between LA and Vegas for example.
I've only heard of one person having been done by one though.
In terms of cost, the justification is probably that the aircraft was going to be there anyway on regular patrols so when things are quiet it might as well recover some costs by nabbing speeding motorists.