Every road in the United States has a speed limit, but where do these numbers come from? Do they actually make people slow down? And do lower speed limits make roads safer? In this episode, Clare tells Teo about the origins of speed limits, the science and engineering behind them, and how they fit into the bigger picture of staying safe on American roadways. 

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Sources in this episode:

• The first speed limit passed in the United States, cultureNOW
• The first state-wide speed limit, ConnecticutHistory.org
• Statement on Signing the Emergency Highway Energy Conservation Act, The American Presidency Project, 1974
• I Can’t Drive 55, Sammy Hagar 
• Impact speed and a pedestrian's risk of severe injury or death, 2011
• Literature review of pedestrian fatality risk as a function of car impact speed, 2011
• Speed Limit Information, Seattle Department of Transportation
• Speed Limit Case Studies Report, Seattle Department of Transportation
• Crash Analysis Database, Seattle Department of Transportation
• Road Segment Counts Database, Seattle Department of Transportation
• Interview with Yinhai Wang, University of Washington
• Interview with Venu Nemani, Seattle Department of Transportation
• Interview with Clara Cantor, Seattle Streets Alliance
• Interview with Michael Smith, Seattle Streets Alliance