City of Austin, Texas To build their case for lower speed limits, the Austin Transportation Department (ATD) conducted a multi-year engineering study that complies with state and federal guidelines. ATD diverged from the historic approach of using the observed 85 th percentile speed as the primary input. ATD, however, determined their recommended speed limits based on the 50th percentile speed measured over several years for hundreds of residential streets throughout Austin as well as context-based data such as bicycle/pedestrian activity, adjacent land use, traffic controls, driveway density, and crash history. In 2020, ATD presented recommendations to the City Council to pass an ordinance to limit downtown and neighborhood streets to 25 mph citywide. The ordinance also set speed limits on several urban core arterial streets. The ordinance also lowered speed limits on specific streets that were studied during the data collection phase. In 2022, ATD overhauled its Transportation Criteria Manual (TCM). While the TCM does not establish speed limits, Section 3 establishes target speeds for city streets based on street classification, walking/biking activity level, and conflict level (see Figure 3). These target speeds shape design and operation decisions and therefore influence the posted speed limit.
Figure 3: City of Austin Target Speed
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