Opening Our Eyes to Accessibility

Map of Access to Downtown Employment Center by Car and Transit from Plan 2040

David Levinson at University of Minnesota’s Center for Transportation Studies has released a new report entitled Access Across America.  An alternative to the Urban Mobility Report and other congestion-focused rankings, Access Across America focuses on accessibility as the key benchmark for a region’s transportation performance. Website is here; full report is here.

Accessibility describes the ease of reaching destinations, and is a function of both travel time on the road and the arrangement of activities with respect to the road network.  Unlike congestion, which measure how fast or slowly you can move on the network with no direct reference to where you can get, accessibility also reflects a region’s land use patterns.

Access Across America measures the accessibility of jobs by car in 51 U.S. metropolitan areas, and compares the current data (2010) to accessibility levels in 1990 and 2000.  Of the metro areas examined, the ten most accessible are:

        1. Los Angeles
        2. San Francisco
        3. New York
        4. Chicago
        5. Minneapolis
        6. San Jose
        7. Washington, D.C.
        8. Dallas
        9. Boston
        10. Houston

Among the study’s other findings:

  • In 2010, the average American could reach slightly fewer jobs by automobile than in 1990 but more jobs than in 2000;
  • Automobile speeds were faster in 2010 than in 2000 (and about where they were in 1990);
  • Job losses have limited accessibility gains associated with faster networks;
  • The average American city is slightly more circuitous in 2010 than in 1990 because roads in newer areas (suburban growth) are not as well connected as those in older areas of the metropolitan region; and
  • People living in many smaller metropolitan areas can reach as many jobs by car as people living in much larger areas within both the 10- and 20- minute time frames.

So how did Atlanta fare? Not so great:

 Atlanta, GA

Overall rank of accessibility to jobs by automobile: #28
In 10 minutes: #51
In 20 minutes: #51
In 30 minutes: #37
In 40 minutes: #15
In 50 minutes: #9
In 60 minutes: #9

In 2010, Atlanta was literally the worst city examined for the ability to access jobs within 10 or 20 minutes.  Its ranking gradually improves as the trips get longer and overall Atlanta is roughly in the middle of the pack.

The trend for shorter distance commutes is also striking.  According to the report, metro Atlanta added 521,000 jobs between 1990 and 2010.  Over that same period, the number of Atlanta jobs accessible within 0-10 minutes decreased by 32%, jobs within 10-20 minutes decreased by 31%, and the jobs within 20-30 minutes decreased by 29%.  In other words, metro Atlanta added a half million jobs over the last 20 years but those jobs are located a long way from where people live.

But all is not lost.  The region’s current transportation plans, including both the Statewide Strategic Transportation Plan and Plan 2040, prominently feature assessibility as a key metric for transportation performance.  The specific variation on accessibilty used in both plans is the ability to access job centers within 45 minutes.

Map of Access to the Perimeter Employment Center from the Statewide Strategic Transportation Plan

Map of Access to the Perimeter Employment Center from the Statewide Strategic Transportation Plan

proposed update to the region’s project selection process under Plan 2040 likewise contemplates the continued use of this measurement.

The increased promence of accessibility as a transportation metric is an important step for the region because it reflects the interplay between transportation and land use.  A 40 mile commute on uncongested roads would not register on the Urban Mobility Report, but is still a long way to travel under any conditions.  Closer to reality, a 40 mile commute on congested roads is much more daunting than a 15 mile commute under similar conditions.  Access Across America‘s focus on accessibility is an important way to quantify the problem, and the use of this metric in the region’s transportation plans is a step toward the solution.