Ignore Tinted Windows

From now on, whenever you pass a bus or a limousine with dark windows, start smiling and waving as if you recognize someone in there. Approach the car for a split second as if you were going to talk to them.

If it's someone who's never been in a limo before (e.g. bunch of teenage girls on the way to a wedding), they will probably temporarily forget that you can't see them and get freaked out. It's fun to imagine the possible scene inside even if you don't know the actual outcome.

Whenever you pass a bus that has tinted windows, stare at the (imaginary) people inside the bus, as if you were critiquing their clothes or hairstyle. Again, the fact that the windows are tinted shouldn't matter; the effect, if enough people in the city do this, will be to negate the feeling of coziness and security tinted windows offer.