The United States is the second-largest emitter worldwide of the greenhouses gases that cause global warming. We released 7,782 million metric tons of greenhouse gases in 2007, a 1.4% increase from 2006. Automobile emissions have been stagnating for the past couple of years due to high gas prices and recession-inspired frugality, but emissions from the transportation sector continue to lead all sectors in carbon dioxide emissions, in large part because we have built our communities so that we have little choice but to drive from activity to activity.

It is hard to envision a "solution" to climate change and energy security that does not involve drastic cuts in our transportation emissions. To date, the national discussion of energy and climate initiatives has focused almost entirely on developing more fuel-efficient vehicles or lower-carbon fuels. Experts acknowledge, however, that all foreseeable technological solutions are sure to be overwhelmed by the astronomical number of miles we all drive.

The good news, though, is that we can make enormous progress simply by shaping future building so that we create more communities where people can accomplish more by driving less. Numerous studies now demonstrate that when people are given the option to live in a less automobile-dependent place, they do indeed drive less.

According to the groundbreaking report Growing Cooler: The Evidence on Urban Development and Climate Change, residents of more compact neighborhoods drive 20-40 percent less on average—and less driving equals less emissions.

If you combine that effort with increased investment in public transit of all shapes and sizes, we can reduce dangerous emissions even more.

Vehicle Miles Traveled (VMT) and land consumption rates are rising rapidly

After the Arab Oil Embargo of 1973 highlighted the fragility of depending on foreign oil, lawmakers began to implement fuel efficiency standards and our average miles-per-gallon rates rose for the first time in years. The improvement in efficiency has been overwhelmed by the sheer increase in the miles we drive, thanks to our increasingly spread-out, automobile dependent development patterns.

Where does my state rank? Click to view the graph and access detailed state-by-state VMT data

Due in large part to our development patterns, Americans drove more miles each year until high gas prices in 2008—and even then, the historic drop in vehicle miles traveled only brought the rates back to their 2005 levels.

With much of our landscapes suited for automobile travel only, the amounts of driving necessary to navigate them increased at alarming rates. Between 1977 and 2001, the number of miles driven every year by Americans rose by 151%, at a rate almost five times faster than the population growth rate.

It's no accident that VMT increased so drastically, as we continue to build and develop more areas where residents have no realistic choice but to drive long distances each day to reach their daily needs. A study published by SGA in 2002 found that the degree of sprawl was the greatest link to a high quanity of vehicle miles traveled. (Measuring Sprawl and Its Impact)

© 2007 David Horsey/Seattle Post-Intelligencier

Energy consumption and our reliance on oil threatens our national interests and security

The cold hard truth? We don't produce enough oil to meet our own high demand.

The United States has been producing roughly 5 million barrels of crude oil a day. The United States is the third-largest producer of crude oil— but we import 58 percent of the oil we use each day (19 million barrels in 2008.) A sizable percentage (18%) of our imports come from an unstable Persian Gulf region. In 2008, half of our imports came from OPEC member nations.

It's not only us. Other developing countries like China (which became the largest green house gas emitter in 2007 and the largest auto market in January 2009, displacing the U.S. both times) and India (developer of the $2500 car) are witnessing huge spikes in the rates of car ownership, and we will be competing with many other countries for a limited supply of imports, becoming more expensive all the time.

Domestic refineries operate at near-capacity, and small disruptions in the supply line can have disastrous consequences on our national economy that requires abundant oil to survive day-to-day. It doesn't take a terrorist act to damage our national security—natural disasters alone can do it. We saw some of this fragility firsthand when Hurricane Katrina knocked refineries offline and cut down supply in some southeastern states. Georgia Governor Sonny Perdue asked schools to take two snow days after Hurricane Rita, estimating that taking buses off the road for two days would conserve 250,000 gallons of diesel fuel during a time when national disaster had threatened the nation's fuel supply line.

Increases in driving brought on by land-use patterns contribute to global warming.

The "Three-Legged Stool"

Cleaner, more efficient technology for vehicles—though needed and useful—will not be sufficient solutions on their own

Increases in fuel efficiency have not been able to keep pace with the increases in driving, resulting in net increases in emissions even as efficiency has improved. Many proposed solutions include plans for renewable energy, lower carbon fuels, or more efficient vehicles—largely overlooking an obvious component: our ever-growing reliance on driving.