Was raised about a year ago.. but I'll suggest it again.
Can vehicles move a bit quicker if they're on an emergency? They seem to never drive any quicker than the speed limit, even on large roads like motorways (or highways to those across the pond). I've roughly measured the time it took to travel between two motorway junctions and it worked out at 68mph. The motorway speed limit is 70mph and a police vehicle could well be entitled and capable of driving twice that at 140mph.
I'm aware there is a difference in speed when zooming in but the logic of this doesn't make sense either.