Many of the world’s most important cities are expanding rapidly without adequate transportation planning, according to a new report released today by the Institute for Transportation and Development Policy (ITDP). The report measures the number of urban residents within a short walking distance of rapid transit using a new metric, People Near Rapid Transit (PNT), and applies this metric to 26 major cities and their surrounding metro regions worldwide. Of the cities surveyed, Paris earned a perfect score, while the metro areas of Washington, D.C., and Los Angeles were among the worst.

“The PNT metric illustrates how unplanned urban and suburban growth focuses on automobiles and only those who can afford to drive,” said Clayton Lane, ITDP’s chief executive officer. “Washington, DC, Paris, and Beijing are major examples of cities that have expanded beyond prescribed political boundaries without effective regional transport plans. Larger integrated rapid-transit networks serve more people and limit climate change—but they don’t grow without foresight and planning.”

ITDP researchers developed the PNT metric to measure the number of residents living within 1 km of rapid transit. This metric, People Near Transit: Improving Accessibility and Rapid Transit Coverage in Large Cities, is a crucial tool for understanding the accessibility of rapid transit in urban areas. The report, released in advance of the United Nations’ Habitat III conference, applies the PNT metric to 26 cities worldwide with high-capacity mass transit systems and the surrounding metropolitan regions.

Increasingly, the outlying regions of cities are home to less wealthy communities. A recent report from the Brookings Institution found that the poor population in US suburbs grew faster than anywhere else in the country, increasing by 64 percent over the past decade. Similar trends have already emerged in most countries worldwide. This growth in poverty is exacerbated by the lack of rapid transit, which limits access to jobs and education in other parts of the cities.

Significantly few cities are investing in rapid transit systems that serve the less affluent communities living outside the urban core, even in Europe and especially in North America. For the 13 cities in industrialized countries that were scored, the average PNT was 68.5%, while the metropolitan regions of these cities averaged 37.3%. The metro areas of the six US cities averaged a score of 17.2%.

“Mass transit systems should grow as cities grow; yet in most cities, governments still rely on automobile traffic as the primary way of getting people around,” noted Lane. “In today’s megacities, road space is already massively congested with car ownership presently at only 10-30 percent, yet building more roads remains a misguided top infrastructure priority. Governments need to better serve the other 70-90 percent of the population without cars, and provide better mobility choices for everyone.”

The rapid transit systems of Seoul and Beijing, the two largest cities in the survey, served the most people by far. Almost 11 million people live within 1 km of each system, and their high PNT scores reflect the population density in this area. This demonstrates the potential of rapid transit to serve a large population and improve urban accessibility.

For cities in low- and middle-income countries, the average PNT score was 40.3%, while metropolitan regions averaged 23.7%. Of these cities, the rapid transit systems in Jakarta and Quito did not extend past the city borders. Almost all of the other systems only served a small fraction of the population living in these outlying areas.

“In many cities, it’s far too easy for municipal governments to ignore the problems on the other side of their borders,” Lane observed. “But cities today do not exist in a vacuum. All metropolitan regions have an urban core, as well as surrounding suburban and rural communities. People in the outer regions cannot thrive without better transportation connections to the core and other outer communities. Government relationships across city and state lines are crucial to meeting the needs of their populations.”

A Critical Tool in Efforts to Limit Climate Change

Expanding and optimizing rapid transit is also critical to achieving climate change targets. According to the US Environmental Protection Agency, cars, light trucks, and SUVs generated one-fifth of all carbon dioxide emissions in 2014 that result from burning fossil fuels in the US.

Governments cannot limit these emissions without rapid transit and compact urban development. In a report released two years ago that ITDP produced in collaboration with the University of California, Davis, researchers estimated that more than $100 trillion in cumulative public and private spending, and 1,700 megatons of annual carbon dioxide (CO2)—a 40 percent reduction of urban passenger transport emissions—could be eliminated by 2050 if the entire world expands public transportation, walking and cycling in cities.

“The impacts from climate change could still be mitigated if there is enough political will,” concluded Lane. “The continuing construction of car-oriented development found in metropolitan regions all over the world is a perfect example of this tragedy. Rapid transit integration, including rail, bus, cycling, walking, and shared car networks, could connect these places sustainably to a wealth of opportunities.”