One of the consequences of urbanization has been the need to transport people and goods to, from, and within cities. Urban transport for people has come to be dominated by the car in the twentieth century, and trucks have increasingly displaced trains for the movement of goods, while public transport, biking, and walking are less frequently used alternatives, especially in North America. The 1990 census in Canada found that 73 percent of working Canadians drove their own vehicle to work while 10 percent used public transport, 7 percent walked, and 1 percent bicycled. On average, North Americans now spend 5 percent of their time in motor vehicles.
Urban sprawl has made the ownership and use of at least one car almost essential for suburban residents. Such low density urban sprawl makes public transport uneconomical and results in high vehicle miles, high fossil fuel consumption, and high levels of air pollution and emissions of carbon dioxide, the main greenhouse gas (see Figure 1, which shows energy use compared to urban density for many world cities). One study in Ottawa, Canada, found that suburban residents walk or cycle one-third as much as people living in the central parts of the city, but they drive twice as far, consume twice as much energy, and produce twice as much pollution.
Unfortunately, these trends are being followed in the developing world; 52 percent of the increase in the world's motor vehicle fleet between 1996 and 2020 will occur in Asia and in Central and South America. On a global scale, transportation accounts for 60 percent of total oil consumption, and this consumption is expected to increase about 50 percent between 1993 and 2010, but twice as fast in the developing world and three times as fast in South Asia.
In addition to outdoor air pollution, the health consequences of urban transportation include invehicle air pollution, motor vehicle accidents (MVAs), noise, and a variety of mental and social affects, as well as the contribution transportation makes to global warming and fossil fuel depletion.
CONSEQUENCES OF URBAN TRANSPORT
Urban Air Pollution. Motor vehicles are a major source of nitrogen oxides (NOx) and volatile organic compounds (VOCs)—which interact to form ground level ozone—and of microscopic particulate matter (PM10). These are the key components of urban air pollution. Globally, outdoor air pollution results in 200,000 to 570,000 deaths annually, with 1.4 billion people exposed to urban air pollution above World Health Organization (WHO)
guidelines. But deaths are only a small part of the problem. Far more serious are the huge numbers of people who become ill. The "health effects pyramid" for PM10, for example, shows that for every death caused by this pollutant there will be 34 emergency admissions, 407 asthma days, 6,085 reduced activity days, and 18,864 acute respiratory symptom days.
In-Vehicle Pollution. A generally neglected aspect of urban transportation is the air quality inside motor vehicles—a place where North Americans spend as much time now as they do outdoors. Levels of benzene (a human carcinogen), carbon monoxide, and nitrogen dioxide may be much higher inside the vehicle, especially in poorly maintained vehicles and in congested, slow moving traffic conditions such as those found in urban settings.
Motor Vehicle Accidents (MVAs). In 1996, MVAs in the United States accounted for 41,907 deaths, 3.5 million nonfatal injuries, and total societal costs in excess of $150 billion. In Canada in 1996, 3,082 deaths resulted from MVAs and there were 249,198 injuries. It is estimated that globally by 2030 there will be over 2 million MVA deaths and 50 million injuries annually, with 5.7
Noise. Traffic is the principal source of noise pollution in the urban environment. The health effects include hearing loss, disturbance of sleep patterns, interference with communication, and degradation in the quality of life, according to WHO.
Mental and Social Effects. In Canada in 1992, only 8 percent of employed Canadians did not commute to work. Average commuting time was forty-eight minutes each day, but sixty minutes in the larger cities; 10 percent of commuters spent more than ninety minutes a day commuting. This contributes to stress (sometimes expressed as "road rage"), increased social isolation, and loss of time available for family and community life.
Global Warming. In 1994 in Canada, transportation was responsible for 31.4 percent of emissions of carbon dioxide. Per capita transportation-related CO2 emissions in Canada and the United States are roughly three times that of other Western industrialized countries. The health impacts of global warming are likely to be significant, and mostly negative.
Other Effects. A 1994 Statistics Canada report refers to a number of other adverse environmental and health consequences of transportation, including increased urban runoff and thus water pollution, solid waste production, habitat destruction, and the partition or even destruction of neighborhoods. In addition, the private car is expensive to own and operate, which can be a real burden for people on low incomes, while urban congestion costs the local economy in terms of wasted fuel, lost time, and health effects. The Organization for Economic Cooperation and Development estimates the external costs of such unsustainable transportation systems to be 5 percent of the GDP.
This litany of adverse health and environmental impacts of transportation has resulted in a growing interest in alternative approaches, including more walking and biking, reduced goods transportation, and improved public transit. The health benefits of a good urban transit system are both direct and indirect. Direct health benefits include lower rates of respiratory and heart disease resulting from reduced pollution; lower accident rates because transit is a safer form of travel; and fitter and healthier people resulting from the more active lifestyle as people walk and bicycle more. Indirect health benefits may include less congestion, reduced commuting time, less noise, less stress, less cost, higher discretionary incomes (especially for low-income families), less social isolation, increased access for disadvantaged groups, the conservation of energy and resources, and reduced global warming.
Ultimately, a healthier urban transportation policy will require a significant change in urban development and land use practices and in the North American way of life. To improve public health in urban areas, it will be necessary to encourage more European-style urban developments with higher densities, mixed land use, strong support for public transport, the creation of pedestrian and bike routes, and policies to restrict the use of private vehicles.
Elmson, D. (1996). Smog Alert: Managing Urban Air Quality. London: Earthrscan.
Fletcher, T., and McMichael, A. J., eds. (1997). Health at the Crossroads: Transport Policy and Urban Health. Chichester: John Wiley.
Newman, P., and Kenworthy, J. (1999). Sustainability and Cities: Overcoming Automobile Dependence. Washington, DC: Island Press.
Schwela, D., and Zali, O., eds. (1999). Urban Traffic Pollution. London: E. and F. N. Spon.
Statistics Canada (1994). Human Activity and the Environment. Ottawa: Author.
U.S. Department of Health and Human Services (1998). Healthy People 2010 Draft Objectives. Washington, DC:U.S. Public Health Services.
Whitelegg, J. (1997). Critical Mass: Transport, Environment and Society in the 21st Century. London: Pluto/World Wide Fund for Nature.
World Resource Institute (1998–1999). World Resources. New York: Basic Books.