The term "aggressive driving" is believed to have been coined by the media, grasping for a single adverb to describe myriad acts of reckless driving. When retaliatory, such acts are called "road rage." The etymology of the term is a study of careless use of the language. Misuse of the term gained popularity (roughly 2 decades old) and has become so ubiquitous in the media that retraction and correction in the short term is very unlikely. Even the NHTSA has partially adopted the misnomer and unfortunately defines 'aggressive'sic driving as occurring when "an individual commits a combination of moving traffic offenses so as to endanger other persons or property." About 18 states have codified laws regarding so-called aggressive driving. Timid is the opposite of aggressive. Careful or prudent would be the opposite of reckless.
Timid drivers creep slowly out into merge lanes, fail to move quickly to avoid dangerous situations, stop in protected merge lanes to see if there is traffic coming, operate vehicles significantly out of step with traffic flow, back up traffic more frequently than their peers, tend towards hesitation, rarely anticipate or look ahead, and typically have not learned to drive as fully functional adults. The timid driver is essentially devoid of a sense of timing. Timid drivers are characterized and motivated by fear rather than confidence. Timid drivers (unlike aggressive drivers) stop without warning, stop where no stop is warranted, fail to act, wait without reason, slow down at unexplained times, and drive too much slower than the rest of traffic.