Transit: The 4 Percent Solution


Wendell Cox at New Geography takes a look at the Brookings data in Transit: The 4 Percent Solution

He says:

Brookings did not examine a 30 minute transit work trip time. However, a bit of triangulation (Note 1) suggests that the 30 minute access figure would be in the range of 3 to 4 percent, at most about 4,000,000 jobs out of the more than 100 million in these metropolitan areas. At least 96 percent of jobs in the largest metropolitan areas would be inaccessible by transit in 30 minutes for the average resident.

He concludes:

More money cannot significantly increase transit access to jobs. Since 1980, transit spending (inflation adjusted) has risen five times as fast as transit ridership. A modest goal of doubling 30 minute job access to between 6 and 8 percent would require much more than double the $50 billion being spent on transit today.

Moreover, there is no point to pretending that traffic will get so bad that people will abandon their cars for transit (they haven't anywhere) or that high gas prices will force people to switch to transit. No one switches to transit for trips to places transit doesn't go or where it takes too long.

Nonetheless, transit performs an important niche role for commuters to some of the nation's largest downtown areas, such in New York, Chicago, Boston, San Francisco, and Philadelphia. Approximately half or more of commuters to these downtowns travel there by transit and they account for nearly 40 percent of all transit commuters in the 50 largest urban areas.

Yet for 90 percent of employment outside downtown areas, transit is generally not the answer, and it cannot be made to be for any conceivable amount of money. If it were otherwise, comprehensive visions would already have been advanced to make transit competitive with cars across most of, not just a small part of metropolitan areas.

All of this is particularly important in light of the connection between economic growth and minimizing the time required to travel to jobs throughout the metropolitan area.

The new transit job access is important information for a Congress, elected officials, and a political system seeking ways out of an unprecedented fiscal crisis.

A four percent solution may solve 4 percent of the problem, but is incapable of solving the much larger 96 percent.


Transit will never serve large fractions of trips to/from work, but I think these very small numbers are deceiving. Cox is claiming that roughly 4% of all jobs are reachable in 30 minutes by transit. What exactly does that mean?

I looked at the methodology in the Brookings report, and these access numbers are designed to tell you what fraction of all jobs in a metropolitan area can be reached on average by someone living in the area. How to do this? Roughly: take every census tract that is transit accessible, and compute the trip time via transit to every job, and then determine the fraction for the region by appropriate weighting.

The result tells us that people do not live, and jobs are not located, such that a large fraction of jobs are accessible quickly by transit. However, what would a similar analysis reveal about accessibility by automobile? Yes, it would be higher, but how much so? I think that the ratio of transit to auto accessibility would be more informative.

Lastly, what data is available that shows how live and work location decisions are made jointly by individuals? For example, if the average commute for a resident of a census tract to all jobs was 45 minutes, but the average commute by residents of that tract was 25 minutes, then clearly those in that tract are making live/work decisions jointly.

The number by mode of course depends on the size of a metro area (in a large area, by definition, a smaller % are reachable in a fixed time, but a larger number of jobs are reachable). The best data (in the world) is available for the Twin Cities, see . More than 50% of all jobs are reachable within 30min by auto, much closer to Cox's numbers for Transit.

I wonder what the data is on spending on roads and highways and other travel during that time period, if it went up 5 times or even more as well. Since all that spending also encourages people to travel by car and live farther away. They may have to look farther out than the metro area, for instance, for Chicago, you'd have to look all the way out to new subdivisions created near the Fox river or beyond, to see the impact of those homes and roads on jobs in the area, since there are plenty of people that commute from that far out.

David Levinson

Network Reliability in Practice

Evolving Transportation Networks

Place and Plexus

The Transportation Experience

Access to Destinations

Assessing the Benefits and Costs of Intelligent Transportation Systems

Financing Transportation Networks

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This page contains a single entry by David Levinson published on June 10, 2011 3:24 PM.

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