Airplanes are also very ironclad.

Not in CA, they're not. California has some very interesting laws on the books:

40801.  No peace officer or other person shall use a speed trap in

arresting, or participating or assisting in the arrest of, any person

for any alleged violation of this code nor shall any speed trap be

used in securing evidence as to the speed of any vehicle for the

purpose of an arrest or prosecution under this code.



40802.  (a) A "speed trap" is either of the following:

   (1) A particular section of a highway measured as to distance and

with boundaries marked, designated, or otherwise determined in order

that the speed of a vehicle may be calculated by securing the time it

takes the vehicle to travel the known distance.

   (2) A particular section of a highway with a prima facie speed

limit that is provided by this code or by local ordinance under

subparagraph (A) of paragraph (2) of subdivision (a) of Section

22352, or established under Section 22354, 22357, 22358, or 22358.3,

if that prima facie speed limit is not justified by an engineering

and traffic survey conducted within five years prior to the date of

the alleged violation, and enforcement of the speed limit involves

the use of radar or any other electronic device that measures the

speed of moving objects.  This paragraph does not apply to a local

street, road, or school zone.

There's lots of language following 40802 (a) (2) that defines local roads, training requirements for use of radar, &c. And 40803 and up say that speed trap evidence is inadmissible in court, witnesses testifying on the basis of speed traps are incompetent, &c.

40802 (b) can be useful for beating a radar ticket. But it's 40802 (a) (1) that's interesting here.

Basically, what this means is that in CA, even aircraft have to pace you. That's why you see Cessnas flying low and parallel to the road, rather than orbiting at a higher altitude with a stopwatch like you do in other states.

On twisty roads, they don't have a chance. Otherwise, there's a fair amount of room to argue that the aircraft cut corners, &c. Note that since winds aloft can't be determined with any great precision, they have to time themselves against ground objects. (I suppose they could use GPS) Obviously, aircraft will work pretty well on I-5.

Of course, IANAL, YMMV, and YGMGOE.

-Zandr
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