With violent crime, quite often you hear yelling and screaming before the gun shots. In the movies, the music changes, but with complacency, there's usually no warning; nobody's worried about anything, and then "wham"—somebody's dead—every day, thousands (and thousands) of times a day, all over the world. When you add it all up, complacency contributes to more unintentional deaths than anything else, especially when you combine it with rushing, frustration or fatigue.
How do people get so complacent that they don't look for transport trucks or that they fall asleep at the wheel? Why do people get so complacent that they don't even think about the risk anymore? (When was the last time you "worried" about your safety as you got behind the wheel?) How do people get complacent enough that they will do something that they know contributes to making a "mind not on task" error, like texting while driving? Or to not use a safety device like a fall arrest harness, which reduces the risk if they do happen to make an error with balance, traction or grip? And finally, since it happens to all of us—we all do get complacent—what can we do to fight it?