A video explainer of the notorious traffic law that explains why some cities have to raise speed limits to enforce traffic safety.
To understand the scale of the challenge that must be overcome to achieve Vision Zero safety goals to eliminate traffic fatalities and to break the strangle hold cars have on U.S. cities, look no further than the 85th Percentile Rule, as neatly explained in the Grist video shown above.
For more background, see past Planetizen coverage of the 85th Percentile Rule.
Read the full story: A 1930s city planning rule has drivers setting their own speed limits
The Weird Way US Cities Set Speed Limits — and Why it’s Changing
The ‘85% rule’ guides speed limits based on how fast most drivers travel, sometimes prompting cities to raise speed limits.
NACTO Recommends Default Safety Setting for Speed Limits
A step toward an overhaul of the way speed is managed on city streets around the country.
After Lowering Speed Limits for Pedestrian Safety, Town Writes 1,000% More Speeding Tickets
Police are enforcing speed limits in the name of public safety in North Haledon, New jersey. Drivers are being urged to respect the speed limit.
Planetizen Federal Action Tracker
A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.
Northwest rail fans eager for Sept. 30 debut of Amtrak’s Airo fleet
Get ready for that new train smell and more seats. But they won’t go faster or run more frequently on the Cascades route in Washington and Oregon.
Trump is considering data centers on 6 states' public land — some state officials say they had no idea
If the administration approves the proposed projects, data center and data center-related developments will cover 17,600 acres of public land.
California high-speed rail accomplishes only one legislative goal in 2026
The majority of the agency's failed pitches were never developed into written proposals.
Sharp cuts to federal passenger rail, public transit funding arrive today
The American Public Transportation Associations estimates the stopgap bill will result in an over 80% cut to federal passenger rail investment and 20% cut to public transit investment.
Chicago to showcase country’s first battery-operated passenger train
Metra estimates the trains will be ready for passenger use around the start of 2028.
FREE Course: Walkable City 1: Why Walkability?
After describing his path towards focusing on walkability as the essence of good planning, Jeff Speck marches through his five principal reasons for making more walkable places.
Reinventing Malls: Planning Alchemy—Turning Gray Fields Into Gold
The course focuses on the opportunities and imperatives that shape reinvention of mall sites.
City of Thousand Oaks
City of Wisconsin Rapids
Harvard University Graduate School of Design
The Architects Foundation
University of Cincinnati Online
Northern Illinois Transit Authority (NITA)
The Pocatello Development Authority
The Urban Renewal Agency of the City of Pocatello