When I had to retake part of my driving test (no infractions, just different norms for towing trailers/caravans in other EU countries) the examiner asked if I always looked in the rear-view mirror obsessively, or was it because it was a test - answer - after working nights and living within 500 yards of police, fire and casualty, I no longer hear any type of siren, not even the new yankee modulating ones j