Despite the critical role traffic signals play in shaping regional mobility, many agencies still rely on outdated systems that can't keep pace with today's traffic challenges. As demand for smarter, safer, and more sustainable transportation grows, traditional signal performance methods - while foundational - are no longer sufficient.

It’s time to rethink how we manage one of the most powerful tools we have to manage traffic flow: the traffic signal.

Aging infrastructure, limited real-time visibility, and reactive processes make it difficult for agencies to optimize signal timing for changing road conditions. 

Traditional performance measures—while useful—struggle with data gaps, accuracy issues, and costly hardware requirements. By leveraging cutting-edge data analytics and automation, agencies can move beyond reactive decision-making and embrace a proactive, data-driven approach to traffic management. It can also be accomplished cost-effectively without the requirement of new hardware. 

‍Understanding Traditional Signal Management and Why It Falls Short

For years, transportation agencies have relied on manual field inspections, Automated Traffic Signal Performance Measures (ATSPMs),  and more recently, Probe-Based Signal Performance Measures (PBSPMs) to evaluate signal performance. While each brought progress, all come with trade-offs that limit their ability to truly modernize traffic management.

‍Manual Field Studies: Expensive and Labor Intensive 

Traffic engineers conduct field observations to record intersection performance, including travel times, delays, stops, and pedestrian crossings, and identify signal performance issues for intersections without connectivity. We all understand this is very costly, slow, and time consuming (70 hours per intersection at $4,500 per intersection, per FHWA). It’s a massive strain on resources and provides only moment-in-time snapshots.

‍ATSPMs: Great Insights, Limited Reach

ATSPMs use high-resolution data logging capabilities to monitor traffic controller performance and generate metrics for signal retiming. ATSPMs provide insights into key signal performance measures, including: 

• Arrivals on green
• Turning movement counts
• Split failures, and more

But ATSPMs have limitations. They don’t provide visibility outside of the detection zone and can’t measure travel time, control delay, queue length, stops and other vital measures that can support a traffic engineer’s understanding of road user experience.

The full adoption of ATSPMs is expensive, due to: 

• High infrastructure costs requiring connectivity 
• Hi-resolution logging capabilities needed for signal controllers

Because ATSPMs rely heavily on detection systems, they often have massive data holes. Flow Labs studies have found only 27.6% of detection devices operating in the field are providing accurate data. This results in 87% of major signal issues being missed, and 5% of major issues identified as false positives. 

‍PBSPMs: Scalable, Not Comprehensive 

Probe-Based Signal Performance Measures (PBSPMs) use real-time probe data from connected vehicles for visibility into driver behavior to understand signal performance. For agencies covering a large region with limited connectivity, PBSPMs provide a hardware-free, scalable solution for signal monitoring and basic signal analysis. 

While these methods provide engineers with tools to better understand signal performance, they come with limitations of data completeness and sometimes lack accuracy due to low probe data penetration rates (typically 3-10%).

With limited diagnostic capabilities, PBSPMs eliminate the ability to identify core issues as it’s not possible to capture broader mobility metrics, such as: 

• Travel times
• Queue lengths
• Vehicle movement beyond detection zones

Introducing the Best of Both Worlds - Integrated Signal Performance Measures

Regardless of whether it’s ATSPMs or PBSPMs, without real-time, high-quality information traffic engineers are forced into reactive decision-making, as their signals become outdated and don’t account for changes in traffic patterns. 

To address the challenges of traditional signal management technologies, Flow Labs developed Integrated Signal Performance Measures (ISPMs), a modern solution that combines the strengths of traditional methods while eliminating their weaknesses. 

ISPMs integrate multiple datasets, including detection, signal, and connected vehicle (CV) probe data, into one AI-powered platform to provide a comprehensive and accurate analysis of signal performance. This approach enables agencies to understand network behavior and adjust signal timing plans, ultimately reducing regional congestion and easing driver stress.

‍ISPMs Aren’t Just a Blend - They’re a Breakthrough

You might be wondering - aren’t ISPMs just a combination of ATSPMs and PBSPMs? The answer is no.

ISPMs go beyond simply adding these two methods together and generate entirely new and unique performance insights. By using AI to combine detection, signal, and probe data into a unified dataset, ISPMs deliver better diagnostics and more informed decision-making than either method alone. 

Let’s Take a Look: the Key Benefits of ISPMs

‍Higher Accuracy 

By combining agency and hardware data with probe data sources, ISPMs deliver information from 20-35% of vehicles driving on any given roadway, a significant increase compared to the current industry standard of 3-10%. Transportation agencies will see higher data accuracy and reliability, which is crucial for effective signal management. 

‍New Performance Measures 

ISPMs provide unique performance metrics not available through ATSPMs or PBSPMs alone, including:

• Accurate turning movement counts
• Red light running detection
• Dilemma zone entry analysis

Enhanced Monitoring 

ISPMs provide a multi-modal perspective that is essential for modern traffic management, enabling agencies to monitor:  

• Signal operations
• Safety
• Mobility
• Asset health

‍Scalability and Cost-Effectiveness

The ISPM approach is scalable and offers a cost-effective solution for regional signal monitoring, making it accessible for agencies of all sizes.

‍Future-Proof Infrastructure

ISPMs provide an effective solution for agencies seeking a scalable, flexible system that captures probe-based, controller-based, and other datasets, all without adding additional hardware. This infrastructure-agnostic approach ensures agencies are prepared for future advancements.

‍The New Era of Traffic Signal Management Starts Now

Agencies no longer have to choose between expensive hardware or limited insights. ISPMs offer a smarter, scalable, and future-proof solution to manage traffic signals with real-time accuracy and proactive control. 

Whether you're responsible for one city or an entire region, ISPMs empower you to:

• Optimize signal timing
• Reduce congestion
• Improve safety for all road users
• Future-proof your infrastructure
• Rely on data-driven decisions 

Stay tuned for our next post in the series, “The Role of ISPMs and AI in Traffic Signal Management.” If you are ready to see ISPMs in action, contact Flow Labs today at sales@flowlabs.ai to schedule a demo.