Photo by sbamueller on Flickr.

It’s well known that air travel generates a large “carbon footprint” because of its greenhouse gas pollution. Less discussed is the carbon impact merely of getting to the airport — the “toeprint” of the flight. The more single-vehicle trips, the bigger the impact. Of many culprit airports across the country, one of the worst is Dulles.

Technically, Dulles is reachable by mass transit. However, the service is so poorly publicized and the transit schedule is so inadequate that it draws few riders. In fact, unlike virtually every other city, it is now literally impossible to take an express bus from downtown to Dulles. The venerable Washington Flyer bus from 16th and K Street was eliminated in 2004.

There is a Flyer bus from the West Falls Church Metro, but of the 17.8 million passengers who use ground transportation to or from Dulles every year, only about 250,000 use it. Another 500,000-or-so use Metrobus Route 5A from L’Enfant Plaza and Rosslyn. Everyone else — more than 17 million persons — either drives his or her own vehicle, rents a car, gets a car ride from a friend or takes a taxi. The waste of fuel (and money on taxis) is considerable.

One problem is the schedule. The Flyer normally operates only every half hour, sometimes less. Bus No. 5A is on a 40- to 50-minute schedule weekdays and hourly on weekends. Considering those schedules and the length of the actual ground travel, it is literally possible to spend more time transiting to Dulles than flying to Chicago.

Complaining to the Flyer management yields the response that there is no demand. “Take a look around you,” they told me. “There are only 10 passengers. We can’t even fill the buses at two per hour, much less if we ran four or six.”

With that kind of faulty logic, a single bus per day would be packed with passengers. Rather, generous scheduling is key to any successful transit service.

There is fantastic demand to get to Dulles. The airport has an astounding 40,000 parking spaces, which consume 300 acres. The problem is that parking and transit are handled by two different authorities with two different profit structures pricing regimes. Neither has any mandate to do anything about the carbon toeprint.

Passengers who drive can park for $10 per 24 hours, which also buys them a free, frequent shuttle bus to the terminal. Since the Flyer costs $10 each way, not including the Metrorail fare to West Falls Church, this inexpensive parking makes it financially advantageous for a single person on a one- or two-day out-of-town trip to drive.

With more passengers in the group, the reward for driving increases. And compared to using a taxi roundtrip, the cost of parking breaks even for about 10 days of travel.

Passengers aren’t the only ones who travel to Dulles. The airport’s workforce is an astonishing 36,000. For every 12 airline passengers and their toeprints, there are an additional nine airline and airport workers driving on the Dulles Access Road and other routes. These people have it even better. Courtesy the Transportation Security Administration, parking for them is free. The Washington Flyer offers Dulles employees a discount of $4 on each bus trip, but how many people with the choice would choose to take a bus for $6 versus driving a car for free?

It’s not that Americans “love to drive” or “can’t be pried out of their cars.” Maybe they just prefer not to be stupid enough to turn down low cost parking and a personalized schedule for expensive and intermittent transit. As for the toeprint — society’s costs of wider highways, wasted gasoline, air pollution, heat island effect, loss of productive land, water pollution from runoff and extra automobiles — those are paid by everyone, even those who use transit.

Solving this problem is not that difficult. It can be done incrementally. After all, creating an airport with 40,000 parking spaces but only two or three half-filled shuttle buses an hour was also done incrementally.

On day one, increase parking rates for travelers by $2 per day, not a devastating increase but enough to nudge a few thousand people onto transit. Simultaneously, reduce the TSI parking subsidy to workers by $2 a day and raise the bus subsidy by the same amount, nudging a few more thousand away from cars.

With this mini-surge in demand, the Flyer and Metro can reduce the headway between buses to 20 minutes and the Flyer can also reduce its fare a bit. One year later, $2 more for all parkers, a slug of additional transit passengers, and a bus schedule of every 15 minutes or maybe even every 10.

The third year, who knows? Maybe $20 parking, continuous low-cost shuttle service, significantly fewer cars on the road, less pressure to widen I-66, cleaner air and the opportunity to start depaving some of the vast expanse of asphalt at Dulles would all become feasible. Finally we’d be going from a cycle that used to be vicious to one that is virtuous.

The United States spent 75 years moving up inexorably from transit to cars. We can climb back down this shaky ladder in the same methodical way, by charging appropriate costs for autos and providing transit levels that match the growth in demand. The place to start is with large public institutions that have predictable ridership and manageable transit modes — places like Dulles Airport.

Peter Harnik, co-founder of the Rails-to-Trails Conservancy, is a retired board member of the Washington Area Bicyclist Association. He currently serves as co-chair of WABA's 50th anniversary Jubilee Committee.