The story so far: Ed Glaeser recently began an effort to assess the costs and benefits of constructing high-speed rail lines at the New York Times' Economix blog. Last week, he posted
his first substantive take on the issue, an attempt to estimate direct
costs and benefits from a hypothetical line between Houston and Dallas.
Dallas' DART transit system. (Photo: Light Rail Now)This effort was riddled with errors.
First among them was the choice of route: a Dallas to Houston line that
doesn't appear on the administration's plan for high-speed rail
construction.
In this week's post
he responds to that complaint by saying he picked a "mythical" 240-mile
span between Dallas and Houston "to avoid giving the impression that
this
back-of-the-envelope calculation represents a complete evaluation of
any actual proposed route" -- which should lead one to wonder exactly
what he's doing here.
He's
unwilling to put his figures on the line as representing a complete
analysis, and yet he's fairly immodest in detailing his conclusions. He
at least owes his readers an assessment of what is being left out, how
important it is, and how its inclusion might alter his findings.
Glaeser's
analysis assumes no population growth -- he bases ridership on current
metropolitan populations -- and no shift in mode share over time,
despite the fact that both Houston and Dallas have rates of transit
ridership well below similar-sized cities (suggesting that with growth,
transit's share will increase) and are rapidly constructing new systems
to facilitate greater transit use.
If one adjusts anticipated ridership figures to correct for these errors, and if one uses a more realistic figure for the value of business traveler time, then benefits appear to come quite close to or exceed costs of construction.
Today,
Glaeser seeks to estimate the environmental and congestion benefits of
high-speed rail, and he quickly stumbles into error once again. Once
more, he fails to take into account population growth, despite that
variable's crucial importance to this analysis.
Instead,
he assumes that rail will merely poach riders from the ranks of current
drivers and fliers. Not only does this miss that in the coming decades
millions of additional travelers will move to the area, but it also
ignores the effect of population growth on congestion costs at highways
and airports.
Houston and Dallas are among the most congested
of the country's largest cities, and growth in annual delays per
traveler in Houston and Dallas has dwarfed increases in delays in peer
cities over the past decade, rising by about 50 percent between 1997
and 2007 compared to increases of around a third or less for the
country's other large metropolitan areas.
Rapid population
growth is overwhelming existing infrastructure between the two cities.
Even if the rate of population growth slows, significant new capacity
will have to be constructed to prevent major increases in congestion
costs.
In that case, one must either update the
environmental analysis to include significantly higher congestion costs
for roads and airports, or one must set the emission costs of new road
and airport construction and set the numbers for new capacity against
the emission costs of rail. Or one can simply do as Glaeser does, and
ignore the whole issue.
Glaeser makes more mistakes as he
goes on. He appears to use the fuel efficiency for passenger cars -- 22
miles per gallon -- even though nearly half of the nation's households
vehicle fleet consists of light trucks, which average only 18 miles per
gallon.
And he writes, "These estimates suggest that trains are green, which differs from the
studies, which include the emissions from building the rail system,
cited by Eric Morris at Freakonomics," when Morris' blog post shows nothing of the sort, and when actual assessments of life-cycle emissions demonstrate that rail is, in fact, very green relative to applicable alternatives.
The
small errors are annoying, but the real problem is the series itself.
This is simply not a credible attempt to understand the costs and
benefits associated with construction of a high-speed rail system.
Rather, it's a bunch of hand-waving concealing the fact that extremely
unrealistic assumptions are being used to reach what are presented as
fairly definitive conclusions.
A well-intentioned analyst
would approach this project with some humility, and would take pains to
inform readers of the many shortcomings of what is an admittedly
"back-of-the-envelope" assessment. But Glaeser can't honestly account
for the factors he omits and still reasonably claim that rail
construction isn't justified by the numbers.
And so we get
this. Next week, the exercise mercifully concludes. Perhaps in his
final installment Glaeser will do more to recognize the failings of his
approach.
