Using accessibility to evaluate future planning scenarios


Recently published, and summarized in CTS Research E-News: Using accessibility to evaluate future planning scenarios:

“Understanding the interdependent relationship between transportation and land use is important for planning the future growth of cities. Recognizing how this relationship affects accessibility—the ability of people to reach the destinations that meet their needs and satisfy their wants—can help policymakers and planners make decisions that optimize a city’s efficiency, livability, and economic competitiveness.
In a study funded by the Minnesota Department of Transportation, researchers from the Department of Civil Engineering compared a set of planning scenarios for the Twin Cities metropolitan area using accessibility as a performance measure. Associate Professor David Levinson, undergraduate research assistant Paul Anderson, and graduate student Pavithra Parthasarathi used the scenarios to evaluate the accessibility of various land use and transportation network combinations.
The researchers analyzed the accessibility of 60 different scenarios, including combinations of six land-use scenarios and 10 highway and transit networks. The land-use scenarios included existing 2010 conditions, projected 2030 conditions, and various combinations of centralized and decentralized population and employment conditions.
Highway networks used in the scenarios included 2010 conditions, projected 2030 conditions, an ideal freeflow network with no congestion, and a hypothetical diamond lane network that added high-occupancy toll lanes to all freeways inside the I-494/694 beltway. Transit networks ranged from 2010 conditions to projected 2030 conditions to a ‘retro’ network that added all 1931 rapid transit streetcar routes to the 2030 network.
In terms of land use, results show that centralized employment and centralized population had the highest accessibility across all networks, resulting in more access to jobs and labor as well as shorter commute times. The researchers found that fully centralized growth produced about 20 to 25 percent more accessibility than the projected 2030 scenario, depending on the accompanying transportation network.
Of the transportation networks, the researchers found that the freeflow network had the highest accessibility—20 percent more than the projected 2030 network—followed by the diamond lane network.
At first, the researchers say, it would be easy to choose the land use and transportation network combination with the highest accessibility as the future planning goal. However, the scenario of centralized population and employment on a freeflow network—while ideal for accessibility—is not likely to be cost-effective or feasible under current conditions.
Instead, the researchers say, these study results could be used to help prioritize future investments and land-use strategies based on how accessibility-effective they are—how much accessibility they deliver per dollar of investment.
A final report on the project, Using Twin Cities Destinations and Their Accessibility as a Multimodal Planning Tool (MnDOT 2012-05), is available on the CTS website.”