Why speed limits don't matter

Justine Underhill May 29, 2025
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0:50 History 5:19 The Peltzman Effect 7:40 Why Speed Matters 10:53 Solutions 12:54 Objections 23:31 Can We Do Better? We set speed limits, we put them on signs, and we expect people to follow them. But in reality, it plays out a little differently. People don’t really drive based on what a sign tells them. So if signs don’t work, what does? MAIN SOURCES Confessions of a Recovering Engineer/ Charles Marohn - https://www.goodreads.com/book/show/54979228-confessions-of-a-recovering-engineer Killed By a Traffic Engineer/ Wes Marshall - https://www.goodreads.com/book/show/201978334-killed-by-a-traffic-engineer Walkable City/ Jeff Speck - https://www.goodreads.com/book/show/13538794-walkable-city Happy City/ Charles Montgomery - https://www.goodreads.com/book/show/13330588-happy-city Development of Crash Research Techniques At the General Motors Proving Ground/ K. A. Stonex and P. C. Skeels - https://onlinepubs.trb.org/Onlinepubs/hrr/1963/4/4-002.pdf A Primer on the Clear Zone/ Daniel S Turner - https://onlinepubs.trb.org/Onlinepubs/trr/1987/1122/1122-010.pdf Roadside Design Guide 4th Edition 2011 https://zc.chd.edu.cn/_mediafile/zhangchi/2015/08/18/14cmvxcyx8.pdf Reducing Speeding-Related Crashes Involving Passenger Vehicles- https://www.ntsb.gov/safety/safety-studies/Pages/DCA15SS002.aspx Effect of Residential Street Speed Limit Reduction from 25 to 20 mi/hr on Driving Speeds in Portland, Oregon/ Jason C. Anderson, Ph.D., Chris Monsere, Ph.D., P.E., and Sirisha Kothuri, Ph.D. - https://www.portland.gov/sites/default/files/2020/pbot-20-mph-speed-study-finalv5.pdf Effects of Raising and Lowering Speed Limits on Selected Roadway Sections - https://www.fhwa.dot.gov/publications/research/safety/97084/97084.pdf Design Factors That Affect Driver Speed On Suburban Arterials/ Kay Fitzpatrick, P .E., Paul J. Carlson, P .E., Mark D. Wooldridge, P.E., and Marcus A. Brewer - https://static.tti.tamu.edu/tti.tamu.edu/documents/1769-3.pdf Complete Streets Speed Impacts/ Peter Savolainen, Principal Investigator - https://mdl.mndot.gov/items/202413 Effectiveness of Traffic Calming Measures in Salt Lake City/ Reid Ewing, S. Hassan Ameli, Debolina Banerjee, Sadegh Sabouri, Akif Hamzah Hashim, and Benjamin Wheeler - https://www.slc.gov/transportation/wp-content/uploads/sites/11/2021/05/U-of-U-Traffic-Calming-Effectiveness.pdf Study of the Impact of Police Enforcement on Motorists’ Speeds/ Virginia P. Sisiopoku and Hitesh Patel - https://www.researchgate.net/profile/Virginia-Sisiopiku/publication/245559162_Study_of_the_Impact_of_Police_Enforcement_on_Motorists%27_Speeds/links/56435e0108ae9f9c13e03ae7/Study-of-the-Impact-of-Police-Enforcement-on-Motorists-Speeds.pdf Speed Management - https://www.itf-oecd.org/sites/default/files/docs/06speed.pdf Reducing Speeding-Related Crashes Involving Passenger Vehicles - https://www.ntsb.gov/safety/safety-studies/Documents/SS1701.pdf Pedestrian Fatalities at Historic High/ Eric Cova - https://smartgrowthamerica.org/pedestrian-fatalities-at-historic-high/ ABOUT JUSTINE I'm a journalist with a background in economics and theater. I worked as a producer and on-air reporter at Yahoo Finance, and I later created a documentary series focused on science and tech at Real Vision. My focus now is on urban design, and I was recently elected to City Council in my hometown of Falls Church VA.

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