Across the U.S., municipalities and transit agencies are grappling with a growing challenge: ensuring safe, reliable, and efficient public transportation in complex and congested urban environments. 

One key factor in this equation is speed management. Often viewed as a general traffic or enforcement issue, designing for speed directly impacts public transit operations, mainly when buses operate in mixed traffic conditions.

Rethinking Speed Limits for Public Transit

Traditionally, agencies set speed limits using the 85th percentile speed, a method developed in the mid-20th century that determines the speed at or below which 85% of vehicles are observed traveling under free-flow conditions. Though intended to reflect actual driver behavior, it was designed primarily for rural or high-speed roadways that lack a dense or complex built environment. 

This approach fails to account for land use or multimodal transportation needs. In practice, it can also result in speed creep, where speed limits gradually increase over time simply because drivers begin to travel faster.

This system creates challenges in walkable, transit-rich corridors where buses constantly interact with people walking, biking, and driving. Speeding in these environments can lead to more frequent and severe collisions, especially around bus stops, crosswalks, and transit transfer points. 

Controlling speed benefits public transit agencies in terms of safety and reliability. Higher speeds and more collisions can mean more frequent disruptions, more extended service interruptions, and a deterioration of the rider experience. This has downstream effects on congestion and driver reliability as well.

Speed Management as a Transit Priority

Effective speed management isn’t just about enforcement. It’s about designing and governing streets to align vehicle behavior with community goals. 

For public transit, this means ensuring that buses can travel safely and predictably, without being subject to the erratic effects of speeding or aggressive driving by other road users. This becomes especially critical in mixed-traffic settings where buses lack dedicated lanes.

Modernizing speed policies helps create a safer environment for transit passengers and operators, who already face daily challenges of navigating unpredictable road conditions, turning vehicles, and pedestrian crossings. 

Proactively addressing speed management allows cities to support transit agencies — and, by extension, their operators — in providing more consistent and safer service. 

New Approaches

A growing movement has recognized the shortcomings of the traditional 85th percentile method. The latest release of the national Manual on Uniform Traffic Control Devices (MUTCD) — the transportation profession’s bible for rule setting — introduces a new framework for setting speeds based on a more context-sensitive approach. 

The National Association of City Transportation Officials (NACTO) is helping to lead the way. 

Rather than relying solely on historical driver behavior, NACTO’s City Limits approach integrates various data sources, such as traffic volumes, crash history, land use context, and real-time speed data, to create a more nuanced picture of street use. This multi-faceted analysis allows transportation professionals to identify corridors where posted speed limits are out of sync with the surrounding environment and where speeding poses the most significant risk to transit users and operators.

Leveraging Technology for Smarter Decision-Making

Advancements in technology are also driving the evolution of speed management. 

Today, cities can deploy a wide range of technology and tools to gather data, evaluate policy alternatives, and implement targeted solutions for ensuring public transit safety with greater precision and impact. 

Key capabilities include:

• Real-time traffic data and insights: Modern platforms can provide minute-by-minute traffic information, including current speeds, travel times, and congestion alerts across all road types, not just major arterials. Transit agencies can pinpoint issues in real time and adjust operations accordingly.
• Historical speed analysis: Access to archived speed data can help transportation professionals analyze traffic trends and assess the long-term impacts of speed management policies on public transit. This is especially valuable when evaluating corridor performance or targeting recurring problem areas near transit hubs.
• Crash hotspot identification and safety analytics: By identifying where crashes occur most frequently and what risk factors contribute to these accidents, cities can prioritize interventions where they will have the most impact, including around bus stops. For example, reducing the speed limit in a high-risk corridor may slightly increase travel time for individual drivers but significantly improve bus safety and reduce delay-inducing crashes.

Together, these capabilities give cities and transit agencies the tools to make informed, evidence-based decisions that improve safety and efficiency for all road users, especially those who rely on public transit.

Building a Speed-Safe Future for Transit

As urban areas grow and mobility needs evolve, public transportation will remain a cornerstone of sustainable, equitable cities. However, to meet users' needs, transit systems must be supported by street environments that prioritize safety and efficiency for all road users.

Rethinking speed limit setting is an essential part of this equation. Moving away from outdated methods and embracing holistic, tech-enabled strategies allows cities to reduce traffic fatalities and injuries while supporting more reliable transit operations. 

Forward-thinking approaches like NACTO’s speed limit setting strategy provide a blueprint for other cities and transit agencies to adapt to their unique needs.

Policy and design are path-dependent. The future of mobility depends not only on investment in buses, trains, and infrastructure, but also on the policies and practices that govern how our streets function. 

More innovative speed management is one of the most impactful, yet underutilized, tools available to help agencies reach their mobility and safety goals for their public transit networks. Now is the time to put it to work.

About the Author: Nat Gale is Head of Product at INRIX, a transportation technology company. His career has been focused on safe and complete streets. Gale brings this experience to developing software and data products that help transportation planners and engineers make smart, more informed safety decisions. He previously ran the City of Los Angeles’ Vision Zero program and was the Director, Capital Projects and Operations, for Hartford, Conn.