Effects of Lowering Speed Limits on Crash Severity in Seattle

This study examines crash severity before and after a speed limit reduction in Seattle, Washington. In November 2016, the default speed limit was decreased to 25 mph (from 30 mph) on arterial streets and 20 mph (from 25 mph) on nonarterial streets. Regression analysis was used to evaluate the speed limit reduction and odds that a crash was fatal (K), disabling (A), or included evident injury (B) for all crashes, crashes on arterials, and crashes on nonarterials. Reducing the speed limit was associated with an overall reduction of 17.2% in KAB injury in downtown Seattle and 7.4% KAB reduction outside of downtown. For arterials, there was a 19.9% reduction in KAB odds downtown and 10.7% reduction outside of downtown. The study suggests that lowering speed limits, accompanied by modified speed limit signs, can increase traffic safety.

• Record URL:
  • https://www.iihs.org/topics/bibliography/ref/2279
• Corporate Authors:

  Insurance Institute for Highway Safety

  Arlington, VA  United States 
• Authors:
  • Hu, Wen
  • Cicchino, Jessica B
• Publication Date: 2023-3

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; References; Tables;
• Pagination: 17p

Subject/Index Terms

• TRT Terms: Before and after studies; Crash severity; Speed limits
• Geographic Terms: Seattle (Washington)
• Subject Areas: Highways; Operations and Traffic Management; Safety and Human Factors;

Filing Info

• Accession Number: 01882587
• Record Type: Publication
• Files: TRIS
• Created Date: May 23 2023 9:27AM