I seem to recall a while back a member here won his case against a speeding ticket because the speed limit signs in a transition zone were obstructed by an 18 wheeler.
Here's a story from one lady who lost her vehicle under the new excessive speed laws because the sign was obstructed:
The Fitzhugh - August 25, 2011
How can you possibly justify a roadside trial and execution for a "crime" the courts in some cases have dismissed?