On this week’s episode, Chuck talks with Dr. Shima Hamidi of the Johns Hopkins Bloomberg School of Public Health, who, in November 2023, published a study on how wide lanes on urban streets promote more crashes, whereas narrower lanes—as narrow as nine feet—are safer. The findings of this paper cut into the core assumptions of the civil engineering profession in regard to traffic design. Strong Towns wrote about the study when it first came out, and we’re excited to now have Dr. Hamidi on the podcast to tell us about her work, in her own words. ADDITIONAL SHOW NOTES Read the study: “A National Investigation on the Impacts of Lane Width on Traffic Safety.” Check out the study’s homepage. Shima Hamidi (Twitter/X). Chuck Marohn (Twitter/X).