The Wrong Way to Set Speed Limits [ST06]

Speed limits are important to keep our roads and streets safe but how are they decided? And what happens when a speed limit is set too high or too low? There are right and wrong ways to set our speed limits, and design our streets, but unfortunately North American traffic planners are firmly stuck in the 20th century when it comes to building safe streets.

To learn more about what’s wrong with North American traffic engineering, check out the new book by Strong Towns founder Charles Marhon, "Confessions of a Recoving Engineer":
https://www.confessions.engineer/


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References & Additional Reading

Understanding the 85th Percentile Speed
Strong Towns
https://www.strongtowns.org/journal/2020/7/24/understanding-the-85th-percentile-speed

ACCIDENTS ON MAIN RURAL HIGHWAYS RELATED TO SPEED, DRIVER, and VEHICLE
https://www.ohiomemory.org/digital/collection/p267401ccp2/id/55

Road safety - Speed
World Health Organization [WHO]
https://www.who.int/violence_injury_prevention/publications/road_traffic/world_report/speed_en.pdf

DRIVING SPEEDS AND PEDESTRIAN SAFETY
https://trid.trb.org/view/365827

Literature review of pedestrian fatality risk as a function of car impact speed
http://transportsafety.ir/wp-content/uploads/Courses/UrbanRoadsafety/Literature-review-of-pedestrian-fatality-risk-as-a-function-of-car-impact-speed.pdf

Paris passe à 30 km/h lundi : les habitants de la capitale plutôt favorables
https://www.leparisien.fr/societe/les-parisiens-plutot-favorables-a-la-limitation-de-la-vitesse-a-30-kmh-29-08-2021-YNSZEQ4RFVHGHLD6BPEEMXIPQM.php

Gezicht in de Carnegiedreef te Utrecht. [1969]
https://hetutrechtsarchief.nl/beeldmateriaal/detail/22e53839-19d0-5e6c-bc97-5d9ed09b1225/media/0a2be07b-15b1-ec18-417c-eda84f33e972

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Chapters
0:00 Intro
0:07 Introduction to the 85th Percentile Speed
1:24 Streets vs. Roads
2:10 Where the 85th Percentile might make sense (roads)
2:38 Where the 85th Percentile doesn’t make sense (streets)
3:44 Momentum kills
4:40 Signs are not enough (driving is subconscious)
5:49 Bad speed limits (city streets)
6:39 Bad speed limits (rural streets)
7:32 Confessions of a Recovering Engineer
7:52 How to make drivers slow down
8:18 Good slow street design
9:05 Safe speeds by design
9:35 OK Boomer
9:55 Conclusion
10:36 Patreon Shout-out
10:48 Outro