AP Human Geography 6.7: Infrastructure

A city's infrastructure is the shared physical systems that people and businesses depend on: transportation (streets, highways, bus and rail transit, ports, airports), utilities (water mains, sewers, power lines, and communication networks such as broadband) and public facilities such as schools and clinics.

The location of infrastructure shapes where development happens. A firm that ships goods wants to be near a highway interchange or a port. An office wants a site its workers can reach. A builder can put up an apartment block only where water and sewer mains reach. Land with that access is worth more, so jobs, investment and housing gather along the networks and thin out away from them.

The chart shows hypothetical City L, the city on the map at the top of the page, in the ten years after it opened its rail line.

Most new businesses opened close to a station, and the count falls with each step away. Networks also work together: only 9 of the 160 opened near the two easternmost stations, which lie beyond the sewer service area on the map. The line did not only serve the city's old pattern; it made a new one. That is a spatial pattern of economic development: where jobs, firms and investment are found across the city, and where they are not.

Two districts can sit on the same networks and still be served very differently. The quality of infrastructure is how well it works: whether the water is safe and steady, whether the power stays on, how fast and reliable the internet is, how often the bus comes, whether roads and bridges are kept in repair.

Poor quality shows up on the map. A factory that loses power every week, or a shop whose street floods after every storm, moves to a district where things work, or never opens at all. Families who can choose move toward clean water, good schools and transit that runs on time, and the districts they leave lose customers and taxpayers.

Take two neighborhoods of a hypothetical city, 3 km apart. Both have water mains, a bus route and broadband. In one, the mains are new and the buses come every 10 minutes. In the other, mains laid 90 years ago break several times a year and the bus comes once an hour. On a map that shows only where the networks run, the two look the same. On a map of new businesses, health and school results, they do not.

That second set of outcomes is social development: people's health, education, safety and access to services. Uneven location and uneven quality both leave the same kind of mark: some districts gain jobs, investment and services, and others fall behind.

Infrastructure is built and repaired by decisions, most of them local. A city council or a regional agency chooses where a new transit line runs, which pipes are replaced first and which streets are repaved, and voters approve or reject the bonds and taxes that pay for them. So a map of a city's infrastructure is partly a map of political power.

Districts with many active voters, organized business groups or wealthy residents can press for upgrades, or block a project they do not want next to them, such as a freeway or a waste plant. Districts with less political voice are more likely to receive those projects and less likely to get repairs. In the twentieth century many cities routed new freeways through low-income and minority neighborhoods, splitting them apart; Topic 6.10 returns to housing discrimination.

Local funding can add a loop. Picture a hypothetical city that pays for much of each district's upkeep from that district's own property taxes. A district with valuable land collects more, keeps its infrastructure in better shape, draws more investment, and so raises its land values again. A district with a small tax base falls further behind with every cycle. The same infrastructure decisions that follow political power can also build it.

Infrastructure also decides who can reach what. A household without a car depends on transit to get to jobs, clinics and grocery stores. If no bus reaches an industrial park, its jobs are out of reach for those households even when the park is only a few kilometers away. Where a city builds schools, clinics and parks shapes social development on the map just as transit does.

The environment is part of the same picture. Highways, ports, rail yards and power plants bring noise and air pollution to the homes beside them. Old combined sewers, which carry stormwater and wastewater in the same pipes, overflow into rivers in heavy rain. Streets with few trees and little green space get hotter in summer than shaded ones. Districts with storm drains too small for heavy rain flood more often, and flooding damages homes and keeps investment away.

Cities also use infrastructure to change a pattern: a new bus line to an industrial park, street trees and parks in a hot district, separate pipes for stormwater so the sewers stop overflowing. Which district gets such a project first is, again, a local political decision.