Complete Streets Speed Impacts

Summary:

Recently, speed management practices have shifted away from an historical focus on the 85th percentile speed toward a safe systems approach that is focused on promoting safer speeds in all roadway environments through a combination of thoughtful, equitable, context-appropriate roadway design, appropriate speed-limit setting, targeted education, outreach campaigns, and enforcement. This includes the incorporation of a Complete Streets approach to roadway design, which uses cross-sectional characteristics that reduce speeds and create a more accommodating environment for people biking and walking. This study aims to inform this design process by advancing our understanding of how drivers adjust their speeds based on changes in the posted speed limit and other contextual factors related to the roadway environment. Field data were collected from 19 highway corridors across Minnesota using handheld lidar guns to track drivers' operating speeds as they transitioned from high-speed rural highways to lower-speed rural and suburban communities. The study results in the estimation of a series of speed reduction factors (SRF), which detail the impacts of various site-specific characteristics on travel speeds. Various features are shown to serve as effective speed-control measures, such as single-lane roundabouts, which reduced speeds by about 7 mph. Speeds were also lower on segments that included two-way, left-turn lanes (0.7 mph), depressed medians (1.2 mph), and raised medians (3.1 mph). The results also show that drivers typically begin reducing their speeds approximately 800 ft upstream of posted speed limit signs and continue to reduce their speeds to a distance 400 ft beyond the sign location. Ultimately, this study will allow for a more proactive and data-driven approach to highway design that considers the needs of all users.

Final Deliverables:

• Report #2024-13
• Research Summary

Related Materials:

• Measuring the Effects of Road Features on Driving Speeds  - (Blog Post)
• New Project Announcement: Complete Street Impacts  - (Blog Post)

Related Research:

• How do Complete Streets Matter for Communities? The Case of Richfield, Minnesota