A lorry driver who waved to motorists to warn them of a speed trap did not obstruct the police, a court has ruled.
Charles Glendinning, 55, from Taunton, was convicted of obstruction, but the ruling was later overturned.
The High Court heard Mr Glendinning, a milk tanker driver, was stopped by police who spotted him waving to tell cars to slow down ahead of the trap.
But judges decided there was no proof his gesture had been seen by any speeders, so it was not "obstructive".
Supporting the decision to overturn the conviction, Lord Justice Scott Baker asked prosecution lawyers what the difference was between Mr Glendinning's arm signal and a sign warning motorists of speed cameras.
Mr Justice Owen suggested that some people might think the police would appreciate "the efforts of others to prevent speeding".
Crown counsel Ben Tabiner said "two completely different strategies" were involved - warning signs were preventative, while a speed trap was specifically designed to catch people.
He said police had set up the trap because earlier that day an average of one driver per minute had been breaking the speed limit on the A303 at Tinkers Hill, Stoke Trister, Somerset.
The judges held that, because there was no evidence that any other drivers were influenced by his signal and slowed down as a result, Mr Glendinning did not obstruct the police.