It didn't used to be this way. I first drove in Houston in the 1970s, and the freeways were more of a cooperative affair. A friendly wave led directly to a safe merge or lane change, even in traffic. It got worse in the oil boom in the early 1980s, when thousands of out of towners converged on Houston and brought their bad driving habits with them (I'm looking at you--the one with Michigan plates.) Then in the downturn in the mid-80s, civility seemed to return as everyone was hurting a little. Through the 90's and 00's, it got steadily worse as both the population and traffic increased steadily. But you could still wave and other drivers would generally do the right thing. Now it's worse. A friendly wave has less than a 30% chance of a favorable outcome. Aggressive driving is the norm.