The point which 4444 and a few others does not seem to understand and did not understand from my post is that a NYC (or area) non-medallion Livery driver is NOT a restaurant minimum wage worker living on tips. Such a person often for the reasons I highlighted above does NOT expect a tip as it is in essence built into their distance fees (incidentally perfectly good livery companies can be arranged to/fr Greenwich and LGA for as little as $70, the most expensive hover around $100, so far from "AT LEAST $120" that we saw written above.....Google it if you want, its not rocket science).
A $20 tip is absolutely excesive, especially considering that no one that has a corporate account, who might in fact be paying LESS at a contract rate would ever tip, and these guys are not expecting it. Again, if you want to throw $5 or $10 at the guy because you feel like it, great! But it is not necessary....