Try Throwing some zaps around!!It works wonders in my country.Or pull a gun on the dudes head!Just joking.Smom people just don't have any manners,and thats the way it is!Nothing we can do to change that.
Generally, drivers in the south do acknowledge, although I must say that I do NOT particularly make a point watching them to check - much prefer to concentrate on driving. Whereever possible I always let buses out and they always say thanks. Never ever however let taxis out - so do not know if they do give thanks but with theit manners doubt it very much.
I drive a van, yes a big white one, and most of the time people are courteous but when there not I just stick up the proverbial finger to show my appreciation....