Originally Posted by
ATNotts
A logical extension of this kind of "policy" is surely that when there are heavy crosswinds making landings difficult we might wind up with "level crossing gates" on motorways that will be closed as every arriving aircraft comes in - just in case something goes pear shaped.
That's not really a logical extension.
The criterion that appears to have been applied here (though we can't be sure) is that an aircraft that has declared an emergency (which we know is the case as it was squawking 7700) is presumed to represent a potential danger to traffic on a busy motorway that it is intending to overfly at low level.
We can argue till the cows come home about how realistic the prospect was of the aircraft falling out of the sky (though of course there have been aircraft declaring fuel-related emergencies that have done exactly that in the past), but it's hard to fault the police who are, after all, programmed to react to the word "emergency" in the public interest.