Sunday, March 03, 2013

Over the top

Alain Bertaud has famously compared Atlanta to Barcelona. They are similar in population size but vastly different in the way of spatial settlement patterns. He finds that Atlanta can never achieve the kind of transit service that Barcelona has.
Barcelona’s metro network is 99 kilometers long and 60% of the population lives at less than 600 meters from a metro station. Atlanta’s metro network is 74 km long – not so different from Barcelona – but only 4% of the population live within 800 meters from a metro station! Predictably, in Atlanta only 4.5% of trips are made by transit vs. 30% in metropolitan Barcelona.
Suppose that the city of Atlanta would want to provide its population with the same metro accessibility as Barcelona does (60% of the population within 600 meter from a metro station), it would then have to build an additional 3,400 kilometers of metro tracks and about 2,800 new metro stations. This enormous new investment will allow Atlanta metro to potentially transport the same number of people that Barcelona does with only 99 kilometers of tracks and 136 stations!

The example above illustrates the constraint that low density imposes on the
operation of transit. I have been comparing metro track length and stations but a comparison between bus lines length and number of bus stops in Barcelona and Atlanta would have given the same results. With its low density of 6 people per hectare – compared to Barcelona 171 p/ha – Atlanta would have difficulties developing a viable form of transit, i.e. a transit system that is convenient for the consumer and financially viable for the operator.

In the case of Atlanta, the very low density precludes developing transit as an alternative transport to the automobile. “Encouraging” higher density, as many reports are fond of recommending, is not feasible either. To reach the 30 p/ha threshold over a period of 20 years, assuming that the historical population growth rate of 2.7% per year continues uninterrupted, the current built- up area would have to shrink by 67 %. In other words, about 67% of the existing real estate stock would has to be destroyed, the land over which it lays has to revert to nature and its population and jobs have to be moved into the 33% of the city which would remain.

The example of Atlanta shows how existing spatial structure constrain the number of alternative strategies available to guide a city development. The lack of spatial analysis often leads to recommending unfeasible strategies.
The Los Angeles urbanized area (according to the 2000 U.S census) covers 1668 square miles, a little less than Atlanta's 1963 square miles. But Bertrand's analysis should confirm that, like Atlanta, LA is not a transit city. Thousands of miles of new track and thousands of new transit stations are not in our future.  A rump system is pointless.

But the dream persists. Today's LA Times includes "Los Angeles' major public spaces remain broken works in progress."  Among the writer's big concerns is the worry that we may never get the famous "subway to the sea" (from downtown LA, west).  "When it comes to transportation in Los Angeles, no dream has remained as stubbornly out of reach as a subway to the sea along Wilshire Boulevard."  In fact all the complaints in the article involve the theme that Angelenos have been slow to make progress becoming Paris-like or NYC-like. Not kidding.  Here is the writer: "If the subway to the sea is an expensive dream worth sticking with, the same can't be said of the city's fantasies of turning Grand Avenue into our Fifth Avenue or Champs-Élysées." New York-envy or Paris-envy as public policy.
The front-page story is part of the Times' contribution to the current mayoral race. Not many people read the LA Times these days, but the sentiment is strong among those who talk and vote in LA.

And some of us thought that sequester-doomsday talk was over-the-top.