The automobile generated the most familiar and most violated branch of law

Evidence

The automobile also created a whole new field: traffic law. There were rules of the road before the automobile, but they were not terribly important. By the middle of the twentieth century, automobile traffic had mushroomed; the automobile touched everybody’s life. States required drivers to get licenses. In the second decade of the twentieth century, the stoplight was invented. Parking regulations, auto insurance: no branch of the law was more familiar to citizens (or more commonly avoided and violated). The first speed limits were imposed early in the century. Traffic violations run into the millions every year; they are, like vagrancy and minor assault cases in police court, the plankton, the krill, of criminal justice. — Lawrence M. Friedman, A History of American Law, 3853