Tuesday, April 23, 2013

Accessibility Study

LA is the most accessible city?

The Center for Transportation Studies at the University of Minnesota is conducting a national study on accessibility (pdf) for the top 51 metropolitan areas. They are looking beyond congestion to focus on accessibility, which they define as the “number of destinations reachable within a given travel time for individual transportation modes”.

According to this study, there are a number of surprising finds. LA is the most accessible city and Portland is ranked 31 overall; at least for accessibility to jobs by auto. That’s an amazing finding considering LA is considered one of the most congested cities in the nation. Granted, Portland as a city, places a high value on alternative forms a transportation and doesn’t focus heavily on auto transport for accessibility.

What makes this kind of study relevant is that it looks at land use and transportation. Combining the two areas of study allows for transportation systems to shift their focus from faster and more direct routes to increasing the density of activities. The shift of focus may help realign planning objectives and goals for cities looking to diverge from the “add more lanes to build out of congestion” mentality.

The Center of Transportation Studies claims this study is the “first systematic comparison of trends in accessibility to jobs by car”. The study is made through a weighted average of accessibility to jobs with higher weights given to closer jobs. The weights are made in 10-minute intervals up to 60 minutes which captures a variety of different commute lengths. Proximity to jobs is calculated as the distance that can be covered in a fixed amount of time given “observed network speeds and observed network circuities”. The number of jobs is averaged by the number of jobs per square kilometer. The study only looks at auto trips, but the methodology can be used in further studies using any mode of transportation.

Currently the study only looks at metropolitan areas. With federal transportation policy losing its influence on the transportation system, the responsibility of transportation planning will increasingly fall to local and state governments. Hopefully, since most land-use planning is conducted at the local level, this kind of study can be adapted, reproduced, and refined for use by local governments as a way to create more efficient transportation systems that are sensitive to a variety of land uses.

Proofread by Mike Armstrong

1 comment:

  1. The Center for Transportation Studies (CTS) report states, “accessibility is the ease of reaching valued destinations.” This statement, I agree with, however what I don’t agree with is the assumption of this article. Throughout the entire report accessibility is understood to be accessibility of auto traffic. However, there are obviously many other forms of accessibility including bicycle, pedestrian and transit accessibility. Also, how accessible to destinations is a city for disabled individuals? No other forms of accessibility are explored at any depth nor are really even mentioned in this article, which I find to be disappointing, especially since this study looks at land use so carefully. But luckily, CJ also picks up on this as well.
    Also, by taking a step back, I would like to assume that with all of this solid land use information, the CTS may use it as a base layer for other, individual future reports such as accessibility for some of the subjects I listed above. It is something I know I will be keeping an eye out for. Thanks for the post, CJ.


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