Car dependency generally means permanently leaning on a car as the only transport mode. However, it can be observed at the city, individual, local, and trip levels. A city is called car-dependent if most of its journeys are by car and offers little incentive to travel by public transport or active mobility. A person is car-dependent if they use a car excessively by choice. Some locations are car-dependent if most journeys that start or end there are by car (for example, an airport or a stadium). Finally, some journeys are car-dependent if they are mostly by car (for instance, travelling between cities).

Cars have created a huge burden in our cities. They create unsafe roads, noise, pollution, and promote sedentary habits. Also, transportation-related pollution has killed millions, and road accidents annually result in the loss of 1.3 million lives, disproportionately affecting pedestrians, cyclists, and motorcyclists. Beyond that, cars require too much space and costly infrastructure primarily dedicated to parked cars.

Although there are some car-free cities, islands, streets and neighbourhoods, it is unrealistic to think that modern cities will soon move to be car-free. Some services (ambulances, police, or firefighters), some journeys, and some individuals (for example, those with a mobility disability) might rely on cars. However, the aim is to design cities with diverse mobility options, where driving a private car is the least preferred option.