The scene is the main road out of White Plains, on a Saturday night. There are a number of cops, and they are stopping each and every car, but only briefly. Cop asks driver “have you had anything to drink tonight”, driver replies in somewhat broken English “just a little”. “How much?” “Only a glass.” “Ok, you can go then.”
Which leads me to the conclusion that either they’re very trusting, or you have to reek of alcohol and be slurring your words before you get breath tested, or have your license inspected.
It’s a bit the same with speeding. Observation suggests that they don’t care if you do 5, 10 or usually even 15 mph over the speed limit, but more than that and you’ve got a court appointment.