Vicious Circle of Congestion

Urban transportation is a highly dynamic system where one component impacts on others, but retroactive (feedback) effects are also to be expected. Congestion is a classic example of this process. Public pressures resulting from a congested transport system may often result in the addition of new capacity such as new or wider roads. This new capacity often results in easier movements and the increased potential mobility may impact on urban sprawl as people may trade more space for a similar amount of time. The outcome is likely to be longer 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 North American cities found themselves in a vicious cycle that triggered an increasing reliance on road transportation and on the automobile.