transit

Housing and automobiles in the United States generate almost 40% of the nation’s carbon dioxide emissions. Emissions vary with an area’s population density and weather patterns.  These in turn affect automotive and transit use, home heating, air conditioning and electricity usage.

There are four primary options for urban transit systems: bus, bus rapid transit, light rail and heavy rail. There has been considerable debate over the systems’ comparative advantages, from lower construction costs to greater carrying capacity.

Train and subway stations play a significant role in both transit networks and the urban environment. While numerous studies have examined stations’ effect on property values, the results have been mixed: Some show a negative impact, others insignificant differences, and some indicate positive effects.

Automotive transportation, one of the largest sectors of the U.S. economy, has numerous societal benefits but also many downsides — pollution, fatalities, congestion. Getting the price individuals pay for driving to reflect its true cost to society is one of the most significant challenges of public policy.

Between 1950 and 1990, while the population of U.S. metropolitan areas grew 72%, the central cities shrank by 17%. Factors that could account for central cities’ population decline include faster commutes, population sorting due to racial and social preferences and perceived increases in city crimes.

Once part of the urban fabric of the United States, streetcars declined as the automobile rose during the 1930s and 1940s. In the last several decades, however, streetcars have returned to popularity — more than 40 new systems are in planning, construction or operation.

Travel demand and vehicle use rates have generally increased from the 1970s through the early 2000s. These trends often inform projections about global energy growth, increases in greenhouse gas emissions and climate change scenarios.

As gas prices rise, people tend to shift from driving personal vehicles to using public transit. However, the extent of this change and the interplay between fuel price spikes and transit usage are not precisely known.

In the quest for increased energy efficiency and smaller carbon footprints, many individuals are now making more conscious consumer choices, looking for greener alternatives in everything from household appliances to hybrid vehicles. However, the basic structure of homes, as well as the areas in which they were built, may represent deep challenges to achieving real cuts in personal and family energy consumption.