Urban transportation is a highly dynamic system where one component impacts others, with retroactive (feedback) effects also to be expected. Congestion is a classic example of a feedback loop through induced demand. Pressures to transport infrastructure managers (usually the public sector) by different user groups being impacted by congestion may often result in adding new capacity, such as new or wider roads. This new capacity often results in lower friction to mobility, and this may impact urban sprawl as people may trade more space for a similar amount of time. The outcome is likely to be an increase in trip lengths, more trips, and eventually more congestion. Consequently, users, through their modal choices, are recursively influencing the development of the urban transport system.
Several motorized cities found themselves in a vicious cycle that triggered an increasing reliance on road transportation and the automobile. This vicious circle can be mitigated if urban population and economic growth stabilize, lifestyles and preferences change, or alternatives such as public transit are more readily available. Irrespective of the location, this vicious cycle remains a challenge for urban planners worldwide.