New York City's transit strike, on the other hand, prompted millions of people to find alternative means of travel, or to forego traveling altogether. With the onset of the two transit strikes, transit travelers had to find alternatives, such as walking, bicycling, getting a ride from a friend or family member, taking a taxi, or trying to find a place in a carpool or vanpool. Complementors and competitors are central to understanding individual behavior when it comes to how, when, and where people travel. Continual transit use, like automobile use or walking, tends to be informed by habitual behavior. A habit is a behavioral tendency to repeat responses and the discipline of psychology defines habit as "learned sequences of acts that have become automatic responses to specific cues, and are functional in obtaining certain goals or end-states." The most important factor in the choice of route is the travel time on the route compared with travel times on alternative routes.