20 Is Plenty: A Vision for Safer, More Livable Streets in San Diego
Imagine a city where every street feels calm, safe, and welcoming—a place where neighbors can walk, bike, and play without worrying about the threat of speeding cars. Cities across Europe, including Amsterdam, Paris, and London have embraced this vision through 30 km/h (20 mph) zones, creating quieter streets and improving quality of life for everyone. More recently, cities in California, like San Francisco, have also adopted slow streets.
San Francisco’s Slow Streets create safe, low-traffic corridors prioritizing walking, biking, and community-building through traffic calming, street design, and public art, fostering a connected, people-friendly city.
Implementing a “Twenty Is Plenty” campaign throughout our neighborhoods would reduce crashes, improve safety, and foster vibrant, people-friendly communities. Here’s why this approach makes sense and how it could work here.
In a well-designed city, not all streets are created equal—some are for high-speed travel, like highways, while others should prioritize safety and comfort for those on foot or bike.
Neighborhood streets and business districts are places where people live, walk, bike, and gather, which means cars should move slowly and predictably in these spaces.
That’s the principle behind 20 mph zones- “Twenty is Plenty”! Reducing speeds to 20 mph dramatically improves safety and quality of life in neighborhoods. Studies have shown that 20 mph zones:
Improve driver reaction times and give drivers more time to avoid crashes.
Shorten stopping distances, reducing the chance of collisions.
Make traffic more predictable, improving the flow of movement for all users.
Increase visibility, allowing drivers to better see and respond to pedestrians, cyclists, and other drivers.
At 20 mph, crashes are far less likely to result in serious injury or death. Pedestrian survival rates exceed 95% at 20 mph, compared to less than 50% at 30 mph.
Street safety exponentially increases by slowing cars to 20 mph
More advantages to Twenty is Plenty include:
Reduced noise
Street crossings made easier
Environments where people feel safe walking, biking, or simply enjoying their neighborhood
Neighborhoods become more inclusive for folks of differing abilities and ages, from 8 to 80
The Vision for Streets Beyond Transportation
Creating 20 mph zones is about reclaiming streets as shared spaces for relaxation, recreation, and community connection. One of our board members shared her personal experience with Diamond Street’s Slow Street in Pacific Beach, a well-intentioned effort that unfortunately fell short:
“I massively enjoyed skating on Diamond when it had physical barriers discouraging traffic. But since the barriers were removed, the current solution of just putting up signs is completely inadequate. It feels like any other street—drivers are no slower or more careful, and it’s no longer fun or safe to skate or walk.”
Her experience highlights a key challenge: temporary solutions without supporting infrastructure can fail to create lasting change. Without physical elements that naturally slow traffic—such as raised crosswalks, chicanes, and street narrowing—streets can quickly revert to car-dominated spaces.
Learning from Other Communities
In Minneapolis, neighborhoods use simple signs that read "Twenty is Plenty" to encourage slower driving. These signs help foster a sense of neighborhood pride.
In San Diego County, the current default speed limit for residential streets is 25 mph. Reducing it to 20 mph would bring us closer to safer standards. A "Twenty is Plenty" campaign could have a powerful impact in making neighborhoods safer and more enjoyable for everyone.
20 is Plenty in Minneapolis
A Strategic Approach to Safer Streets
Achieving this vision requires a combination of policy changes, infrastructure improvements, and community engagement:
Lower Default Speed Limits: We must advocate for reducing the default speed on residential and business oriented streets to 20 mph.
Implement Traffic-Calming Infrastructure: Use physical design elements like raised intersections, narrowed streets, and chicanes to naturally slow traffic.
Launch a Community Sign Campaign: Residents can place "Twenty is Plenty" signs in their yards to promote neighborhood safety and build public support.
As one board member noted, piecemeal approaches can create unintended consequences, such as traffic rerouting to untreated streets. Success lies in comprehensive planning and incremental change that builds broad public support.
Portland’s bike bus is thriving! 🚲👧👦 Safe, slow streets make it possible for kids to ride to school together, building independence, confidence, and a love for biking!
The Future of San Diego’s Streets
By embracing 20 mph zones, San Diego has the chance to create safer, more livable neighborhoods. The pandemic-era Slow Streets initiative was a step in the right direction, but we can go further.
It’s time to reclaim our streets—not just for cars, but for people. Let’s make "Twenty is Plenty" the new standard and build a San Diego where everyone can walk, bike, and thrive safely.
