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I’m writing this on an MD-88 over southern Virginia between IAD and ATL. The clouds are rushing by and I feel perfectly safe. Most air mishaps happen within 1,000 feet of the ground.

This flight is full, like so many in the renaissance of passenger air in the US. Airlines have gotten very good at selling the number of seats we need, and no more. This airplane is as efficient as it could be, per passenger mile. It would certainly require more energy to move me from Washington to Atlanta in traffic. It may even be more energy efficient that Amtrak, as trains are not usually this full.


Up in the air, over North Carolina, we have no land use impact. The great thing about t flying is that it’s done in plentiful 3D space. With a 5-mile horizontal and 1-mile vertical separation requirement, crowding of airways between airports is not a problem in most of the world. There are two places on this trip that require a great deal of land, however: The two airports, IAD and ATL. Two of the largest airports in the US, by site area. The runways alone involve acres* of the thickest, stiffest pavement you can get. It is richly important that the runway be smooth when landing this 80-ton jet. The highway circulation and parking around each airport requires additional square miles of land at each airport**.



Even though I’ll spend most of this trip out of anybody’s way, this trip does have a land use needs. Big ones. This flight could not have occurred without all that space being used on the ground at my origin and my destination. Our more everyday trips, like driving, taking transit, biking or walking also require space and resources at the beginning, end, and along the way.

This is one reason that transportation is about land use.

Every day, I get in a car in the parking lot near my home and drive along lanes that are twice as wide as my car to other parking lots near my cafes, work, dry cleaners, stores, or school. If I want to go to the area’s best parks and hiking trials, I drive to their parking lots. My car only takes up 0.7% of an acre at each parking lot, but the places that I go don’t just serve me, they are available to the maximum possible load of possible cars that could ever want to park in each lot. That’s why we have 800 million parking spaces for 300 million cars. Property owners build parking lots for dozens, hundreds or even thousands of people with the assumption that everyone they want to see in those places has to arrive by traffic.

And they’d be right.

There are a couple of good restaurants and a drug store within walking distance of home, and three cafes within biking distance. I can walk out my front door and walk to their front door, within 5 minutes. To bike, I unlock my bike garage in our back yard, haul the bike out, and drive it to the café. A bannister usually suffices for a bike rack when I get there.

The problem is that the walk is pretty barren, and the bike drive is downright dangerous, So more often than not, I just drive. The value of real estate and infrastructure given to me to allow this cheap seat in traffic may be greater than the cost of gas I put in the car.

The landscape around me is built for traffic, and is minimally usable for walking or biking. Walking or biking are an afterthought and an inconvenience to the free flow of traffic.

Speaking of inconvenience, consider transit. This is the only mode where I can’t just get going, but have to wait for a bus or train to pick me up at a designated stop and take me to another stop. The land needed for this is negotiable, including a bus pullout off the side of the road, a train station with bridges to pavilions in different neighborhoods, an elevator to an underground platform, or a pole on the side of the road with the transit agency’s logo on it. There is no inherent need for space at a transit stop, but sometimes consuming a lot of space makes the transit more visible, as with elevated stations, or usable, as with bus pullouts.

Just as there is no inherent size for a transit stop, there is no inherent need for a transit rider to get in traffic after getting off transit. A transit rider can walk or bike to where they are going, provided what they need is within walking or biking distance of their transit stop. I haven’t got the data to hand, but I hypothesize that most transit riders are traveling to a destination within walking distance of their destination stop.   The impact of each transit stop could be magnified with an easy model for biking to transit stops. The 15 minute walk distance is a quarter mile, the 15 minute bike distance is almost 3 miles.

What’s within a quarter mile or three miles of most transit stations is a place built for traffic: signalized intersections, crosswalks that allow occasional access, roads wide enough to carry peak traffic at a tolerable pace and traffic for the rest of the day at a dangerous pace, and parking lots required of every property to keep cars off the roadways when not in motion. Traffic doesn’t work without routine impacts to land use that have been required for the last 80 years. Parking spaces everything apart to unwalkable distances, high speed traffic makes biking the realm of adrenaline monkeys and daredevils, and the scale of a landscape built for traffic is unusable for transit routes.

With so few people able to walk to each transit stop, there is little reason to run buses very often to much of America. An empty bus is more of a gas guzzling, carbon belching monstrosity than even the International CXT

Yes, they weren’t kidding.

So what would it mean for transit to affect land use?

More jobs, housing, shopping and parks (not parking) within walking and biking distance of each stop or station. Many transit stops are completely surrounded by drivable suburbia. A bus stop on the edge of a parking lot next to the highway is a frequent and futile site for all but the people who work in that strip mall or live in those garden apartments.

What would it mean for biking or walking to affect land use?

More jobs, housing, shopping, and parks within biking or walking distance of where they live or work, and along streets that are safe and interesting to bike or walk along. Interesting because they are full of places to bike or walk to, not spaced apart by mandatory parking lots between the street and the buildings. People in historic city centers and some New Urbanist developments get this at a price premium. It is more expensive because it is

A) better and

B) rare.

We don’t build a lot of walkable/bikable places in the US because they violate the default. They have no place where they must be, the way a parking lot must be next to every development that wants a driveway.

A good place for walkable and bikable places would be next to transit stops.

* One reason this article was delayed was that I was trying to get a runways, taxiways and parking lots polygon layer into GIS.  OpenStreetMap is remarkably coy on this front.  If I had such areas, I would divide that area by the annual passenger traffic and divide that by the number of working hours in the year to get an approximate space consumption per passenger.  Assuming a passenger uses an airport for an hour.  I’ll add this to the list of lampposts I’d like to look under for data

** Many air passengers have to drive their vehicles to the airport and leave them there while on their trips. My own car was just one of the thousands parked at IAD this weekend.