The Hitchhikers Guide to Transit Oriented Density

In the 2005 film The Hitchhikers Guide to the Galaxy, the protagonist of the story, Arthur Dent, has this conversation with his friend Ford Perfect shortly after Ford reveals that he is actually from another planet:

Ford: Remember how we met? That car was racing toward me, I was trying to greet it, you pushed me out of the way?

...Didn't you think it was strange I was trying to shake hands with a car?

Arthur: I assumed you were drunk.

Ford: I thought cars were the dominant life form. I was trying to introduce myself.

Even as a native of planet earth, I think I can understand some of Ford’s initial confusion. I was in Atlanta a couple of years ago for a conference at the downtown Hilton. I was looking out my hotel room window and remarked to the person standing next to me “its all parking”. This person was confused by my abrupt statement so I continued,”I mean don’t just look at the surface lots and parking garages, even the high-rise buildings are mostly parking until you get several floors up, this entire town is one big parking garage.”

Downtown Atlanta

Transit advocates have long recognized the important impact land use patterns can have on the viability of transit. Specifically the density of development adjacent to a transit corridor. Density is often spoken about in terms of “dwelling units per acre”, I’ve also heard it discussed in terms of “jobs per acre”. An easy way to think about density is to imagine a neighborhood. On average, if the houses in the neighborhood have a lot size of 1/2 an acre, then you could say that neighborhood has a density of 2 dwelling units per acre.

Dr. John Holtzclaw of the Natural Resources Defense Council asserts that the threshold where people begin riding transit is somewhere between 5 and 10 units per acre, and it optimizes somewhere around 30 units per acre where it will plateau and only increase modestly as density increases. Daily driving trips however, will continue to decrease as density increases past 30 units per acre and ultimately transit trips will eclipse driving trips around 110 units per acre (think Manhattan).

So its safe to say that a certain level of density is required in order for transit to be viable. A point that I feel is not talked about enough is how the quantity of available parking effects transit and traffic congestion in general. Donald Shoup, author of The High Cost of Free Parking, and Michael Manville of UCLA’s Department of Urban Planning in a 2004 journal article titled "Parking People and Cities" compare Los Angeles, San Francisco, and New York. They point out that both New York and San Francisco place limits on the amount of parking that can be constructed with new development while Los Angeles, like many places throughout the US, mandates the minimum amount of parking that shall be constructed and places no limit on how much can be constructed. The problem with this type of policy is that there is a limit to the amount of automobile traffic any street can accommodate because of its limited right of way, but if growth continues in an area with minimum parking requirements, parking will continue to increase beyond the capacity of the city’s road infrastructure to successfully handle the traffic. The Los Angeles region is the most dense region in the country, yet most transit and “Smart Growth” advocates would say it ranks pretty low on the list of models for quality growth. Shoup and Manville also point out that the San Francisco and New York regions are very dense near their centers and surrounded by low density suburbs, while Los Angeles has a slightly lower density at its center and is surrounded by very “dense” suburbs.

They go on to state:

New York and San Francisco urbanized areas look like Hong Kong surrounded by Phoenix, while Los Angeles urbanized area looks like Los Angeles surrounded by ... well, Los Angeles...

We suspect that what is emerging in LA is a car-oriented density, a condition fostered by the city’s minimum parking requirements. Because parking requirements are essentially automobile subsidies that are yoked to new development, they offset many of the benefits of increased density...

Los Angeles is both car-oriented and dense; it approaches the human density of San Francisco but dilutes it with the parking supply of a suburb. Many benefits it might derive from its density are offset by its relentless accommodation of the automobile.With off-street parking requirements, increases in density simply bring more cars, more congestion, and more air pollution, to say nothing of increased disruptions in the urban fabric and more money redirected away from buildings and toward cars.

Car-oriented density is the phenomenon that I observed from my hotel window in downtown Atlanta, I just didn’t have the words to describe it at the time. I suppose a way to describe a better alternative to this type of urban environment would be transit-oriented density.

Shoup and Manville go on to recommend that one of two things be done to address the issue of car oriented density. The first option would be to set parking maximums instead of minimums, perhaps using the same numbers cities are using today and make it a ceiling instead of a floor. The other option would be to deregulate parking completely and let the people who want parking pay for it. This is the route that Metro Nashville has chosen to take with their final draft of the proposed Downtown Code. While deregulating parking requirements doesn’t completely prevent Nashville from becoming the next Atlanta, it does go a long way in the right direction. This also means that people will need other transportation options in order to get around and that means, you guessed it... transit. I believe if there is transit-oriented density in our future, then no one will be left to wonder who the dominant life forms are on this planet.

- Jay