When automobile trips exceed 75% of all personal trips (such as commuting and shopping), a situation of high automobile dependency is observed. In the United States, 76% of all commuting trips are done using an automobile. Automobile dependency ranges from low where a set of transportation alternatives (transit) are available to high where little if no alternatives outside automobile use are possible. Automobile dependency is also linked with the urban spatial structure as cities with a low level of car dependency tend to be centralized with high levels of density, while cities with a high level of automobile dependency are dispersed. Low density and high automobile dependency are therefore interrelated.