Urban Transport Challenges
Cities are locations having a high level of accumulation and concentration of economic activities. They are complex spatial structures supported by infrastructures, including transport systems. The larger a city, the greater its complexity and the potential for disruptions, particularly when this complexity is not effectively managed. Urban productivity is highly dependent on the efficiency of its transport system to move labor, consumers, and freight between multiple origins and destinations. Additionally, transport terminals such as ports, airports, and railyards are located within urban areas, help anchor a city within a regional and global mobility system. Still, they are also contributing to a specific array of challenges. Some challenges are ancient, like congestion (which plagued cities such as Rome), while others are new like urban freight distribution or environmental impacts.
Congestion is one of the most prevalent transport challenges in large urban agglomerations. Although congestion can occur in all cities, it is particularly prevalent above a threshold of about 1 million inhabitants. Congestion is particularly linked with motorization and the diffusion of the automobile, which has increased the demand for transport infrastructures. However, the supply of infrastructures has often not been able to keep up with mobility growth. Since vehicles spend the majority of the time parked, motorization has expanded the demand for parking space, which has created footprint problems, particularly in central areas where the footprint of parked vehicles is significant. By the 21st century, drivers are three times more likely to be affected by congestion than in the latter part of the 20th century.
Congestion and parking are also interrelated since street parking consumes transport capacity, removing one or two lanes for circulation along urban roads. Further, looking for a parking space (called “cruising”) creates additional delays and impairs local circulation. In central areas of large cities, cruising may account for more than 10% of the local circulation, as drivers can spend up to 20 minutes looking for a parking spot. This practice is often judged more economically effective than using a paying off-street parking facility. The time spent looking for a free (or low cost) parking space is compensated by the monetary savings. Parking also impairs deliveries as many delivery vehicles will double-park at the closest possible spot to unload their cargo.
Identifying the true cause of congestion is a strategic issue for urban planning since congestion is commonly the outcome of specific circumstances such as the lack of parking or poorly synchronized traffic signals.
On par with congestion, people are spending an increasing amount of time commuting between their residence and workplace. An important factor behind this trend is related to residential affordability as housing located further away from central areas (where most of the employment remains) is more affordable. Therefore, commuters are exchanging commuting time for housing affordability. However, long commuting is linked with several social problems, such as isolation (less time spent with family or friends), as well as poorer health (obesity). Time spent during commuting is at the expense of other economic and social activities. However, information technologies have allowed commuters to perform a variety of tasks while traveling.
Many public transit systems, or parts of them, are either over or underused since the demand for public transit is subject to periods of peaks and troughs. During peak hours, crowdedness creates discomfort for users as the system copes with a temporary surge in demand. This creates the challenge of the provision of an adequate level of transit infrastructures and service levels. Planning for peak capacity leaves the system highly under-used during off-peak hours, while planning for an average capacity will lead to congestion during peak hours.
Low ridership makes many services financially unsustainable, particularly in suburban areas. Despite significant subsidies and cross-financing (e.g. tolls), almost every public transit system cannot generate sufficient income to cover its operating and capital costs. While in the past, deficits were deemed acceptable because of the essential service public transit was providing for urban mobility, its financial burden is increasingly controversial.
These difficulties are either the outcome of intense traffic, where the mobility of pedestrians, bicycles, and other non-motorized vehicles is impaired, but also because of a blatant lack of consideration for pedestrians and bicycles in the physical design of infrastructures and facilities. On the opposite side, the setting of bicycle paths takes capacity away from roadways as well as parking space. A negative outcome would be to allocate more space for non-motorized transport than the actual mobility demand, which would exacerbate congestion.
Most roads are publicly owned and free of access. Increased traffic has adverse impacts on public activities, which once crowded the streets such as markets, agoras, parades and processions, games, and community interactions. These have gradually disappeared to be replaced by automobiles. In many cases, these activities have shifted to shopping malls, while in other cases, they have been abandoned altogether. Traffic flows influence the life and interactions of residents and their usage of street space. More traffic impedes social interactions and street activities. People tend to walk and cycle less when traffic is high.
Cities facing the aging of their transport infrastructure have to assume growing maintenance costs as well as pressures to upgrade to more modern infrastructure. In addition to the involved costs, maintenance and repair activities create circulation disruptions. Delayed maintenance is rather common since it conveys the benefit of keeping current costs low, but at the expense of higher future costs and, on some occasions, the risk of infrastructure failure. The more extensive the road and highway network, the higher the maintenance cost and its financial burden. The same applies to public transit infrastructure that requires a system-wide maintenance strategy.
Pollution, including noise generated by circulation, has become an impediment to the quality of life and even the health of urban populations. Further, energy consumption by urban transportation has dramatically increased, and so the dependency on petroleum. These considerations are increasingly linked with peak mobility expectations where high energy prices incite a shift towards more efficient and sustainable forms of urban transportation, namely public transit. There are pressures to “decarbonize” urban transport systems, particularly with the diffusion of alternative energy sources such as electric vehicles.
The growth in the intensity of circulation in urban areas is linked with a growing number of accidents and fatalities, especially in developing economies. Accidents account for a significant share of recurring delays from congestion. As traffic increases, people feel less safe to use the streets. The diffusion of information technologies leads to paradoxical outcomes. While users have access to reliable location and navigation information, portable devices create distractions linked with a rise of accidents for drivers and pedestrians alike.
The footprint of transportation is significant, particularly for the automobile. Between 30 and 60% of a metropolitan area may be devoted to transportation, an outcome of the over-reliance on infrastructures supporting road transportation. Yet, this footprint also underlines the strategic importance of transportation in the economic and social welfare of cities as mobility is a sign of efficiency and prosperity.
Globalization and the materialization of the economy have resulted in growing quantities of freight moving within cities. As freight traffic commonly shares infrastructures supporting the circulation of passengers, the mobility of freight in urban areas has become increasingly controversial. The growth of e-commerce and home deliveries has created additional pressures in the urban mobility of freight. City logistics strategies can be established to mitigate the variety of challenges faced by urban freight distribution.
Many dimensions to the urban transport challenge are linked with the dominance of the automobile.