The Noblis Open Source Accessibility Toolkit

An open source approach to measuring transportation accessibility

Transportation accessibility is defined as access to destinations, particularly people’s ability to reach desired goods, services, activities, and places. In other words, transportation accessibility seeks to answer the question, “How easy is it to reach a desired destination?”

Accessibility is an important transportation metric to the American Association of State Highway and Transportation Officials (AASHTO), the Bipartisan Policy Center’s National Transportation Policy Project, and other organizations dedicated to improving the effectiveness and efficiency of our nation’s transportation systems. Historically, calculating accessibility has been complex and resource intensive. The Noblis Open Source Accessibility Toolkit (OSAT), a set of software tools designed to analyze transportation accessibility and create visualizations to effectively communicate the results, offers a new approach to accessibility analysis. OSAT is simplifying the calculation process, making it more cost effective to do analysis, and engaging a wider user base.

Encouraging Innovation By Removing the Cost Barriers Associated with Accessibility Tools and analysis

In order to achieve its goal of reducing the time and cost barriers associated with performing accessibility analysis, Noblis built OSAT around General Transit Feed Spec (GTFS) transit data, OpenStreeMaps, OpenTripPlanner, and U.S. Census data. Noblis’ geographic visualization tools, designed as a part of OSAT, can be used separately for generating two and three dimensional geographic representations of any type of data.

Unlike mobility-focused metrics such as travel, speed, or congestion, accessibility is mode-neutral which makes it an important performance metric for transportation. OSAT can be used to calculate traditional opportunity and gravity model-based accessibility measures, as well as estimates of the modal accessibility gap (the delta between automobile and transit access). OSAT can also calculate regional, normalized transportation-focused metrics, such as the average percentage of jobs reachable within a given amount of travel time.

Download Noblis’ OSAT

Noblis’ OSAT is freely available to the transportation community under an open source license. All software, documentation, sample input and output data, and sample visualizations can be downloaded at

By opening the door to much broader use, OSAT’s approach to accessibility is enabling a larger array of stakeholders to perform accessibility analysis and helping develop a foundation for innovative transportation solutions that will carry us into the next generation of transportation services.

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