Smarter Signals for Smoother Streets: How Adaptive Signal Control Technologies (ASCT) are Reshaping Urban Mobility
As cities grow and transportation networks become more complex, the demand for intelligent, data-driven traffic solutions has never been greater. At Gorove Slade, we’re excited about the role that Adaptive Signal Control Technology (ASCT) plays in shaping the future of mobility, helping agencies reduce congestion, improve safety, and deliver a better experience for all road users.
What Is Adaptive Signal Control?
Adaptive traffic signals continuously adjust to real-time conditions, unlike traditional signal systems that operate on fixed or scheduled timings. They’re able to adjust the timing of red, yellow, and green lights to accommodate changing traffic patterns and ease traffic congestion when necessary. Adaptive Signals use algorithms within traffic signal controllers to adjust signal timings every few minutes based on real-time traffic information to reduce congestion. Using a network of sensors, cameras, and connected software, Adaptive Signal systems analyze live traffic data and dynamically change signal timings to improve flow and reduce delay.
Intersection of Beverleys Mill Rd and Broad Run Church Rd on US 15, equipped with InSync adaptive signals that adjust in real time to reduce delays and improve safety as part of VDOT’s pilot ASCT project.
Types of Signal Systems
Actuated-Coordinated Signals
On busy commuter routes, most drivers are familiar with driving under an actuated-coordinated traffic signal control system. According to the Federal Highway Administration (FHWA) Traffic Signal Timing Manual, a fully actuated signal is one where all phases at an intersection are actuated. Meaning each vehicular movement requires vehicle detection by means of a loop detector to be served. The FHWA also defines coordination as the synchronization of multiple intersections to enhance the progression of vehicles, particularly in one or more directions in a system. Together, these concepts form an actuated-coordinated signal system.
In this setup, the traffic lights still respond to detected vehicles at each intersection, but they do so within a coordinated timing pattern designed to keep traffic flowing efficiently along the entire corridor. Think of it as a compromise between being responsive to immediate traffic conditions at each intersection while still maintaining an overall rhythm that helps vehicles move through multiple signals without unnecessary stops.
- Pros: Balances responsiveness and progression for moderate traffic volumes.
- Limitations: Still restricted by predefined schedules; lacks real-time optimization across the corridor.
Adaptive Signals
In contrast, adaptive signals collect and analyze real-time data from multiple intersections and adjust operations using AI-based algorithms. Adaptive signals continuously adjust signal phases, green times, and cycles based on current traffic conditions using real-time data. They do not rely on static plans and provide corridor- and network-level optimization, responding immediately to changing conditions and improving overall traffic performance across corridors and networks.
Why It Matters: Benefits of Adaptive Traffic Signals
The network-level effect of ASCT is significant because benefits accrue for all road users, not just drivers. With traffic moving more efficiently and with fewer sudden stops at intersections, cyclists can more safely and easily navigate alongside cars. The improved flow creates a more predictable and comfortable experience for those choosing bikes as a mode of transport.
For pedestrians, ASCT can reduce long waits at crosswalks and make intersections safer to cross. Because the system responds to what’s actually happening on the street—not just a preset schedule—Pedestrians get more timely and consistent crossing opportunities, improving both safety and convenience.
Additional advantages include:
- Eliminating Inefficiencies: Adaptive signal systems can reduce travel times by up to 40% on certain corridors. In Bellevue, WA, travel times dropped by 43% on NE 8th Street and 36% on Factoria Boulevard after deployment. [Time Magazine article on Bellevue’s adaptive signal results]
- Responsive to Unexpected Events: By adjusting to conditions such as crashes or special events in real time, these systems help maintain safer, more predictable traffic flow. [FHWA Adaptive Signal Control Technologies Brochure]
- Lower Emissions: Adaptive traffic signal systems can significantly reduce vehicle emissions by minimizing idle time and improving traffic flow. The FHWA highlights that adaptive signal control technologies can reduce fuel consumption and improve air quality by diminishing the environmentally damaging impacts of congested roads with stop-and-go traffic and long periods of idling. [Enhancing Transportation: Connecting TSMO and Environment]
Case Studies in Adaptive Signal Control
In Gorove Slade’s backyard and across the US, this technology is making an impact. Here are three examples of ASCT in action.
- The Virginia Department of Transportation (VDOT) has played a pioneering role in deploying ASCT through a statewide pilot program launched in 2011. In collaboration with Rhythm Engineering, VDOT implemented the InSync system on 13 corridors to dynamically adjust signal timing in real-time based on actual traffic flow. One such corridor includes a 9.4-mile segment from US Route 15 (Lord Fairfax/ James Madison Highway to State Route 215 (Vint Hill Road), featuring six signalized intersections in Fauquier County. This initiative aimed to address the limitations of traditional time-of-day signal plans, especially under conditions of changing traffic demand due to seasonal fluctuations, incidents, or special events. The evaluation of these deployments showed a 17% reduction in crashes at intersections with ASCT. It demonstrated overall improvements in corridor travel time and efficiency, supporting further adoption of smart signal technologies across Virginia. [VDOT’s Role in Advancing Traffic Signals]
- The City of Alexandria, VA, is deploying adaptive traffic signal control along Duke Street as part of its broader Smart Mobility Program. This initiative aims to reduce delays, improve travel times, and prioritize public transit, especially buses, on one of the city’s most congested corridors. Gorove Slade is proud to have partnered with the City on its Duke Street in Motion project, particularly in relation to the implementation of advanced signal control strategies in the context of the future bus rapid transit (BRT) on the corridor.
- In Maricopa County, Arizona, the Department of Transportation (MCDOT), in collaboration with the AZTech Regional Partnership and the cities of Surprise, Peoria, Glendale, Phoenix, and Scottsdale, is deploying Adaptive Signal Control Technologies along the 16-mile Bell Road corridor. [Maricopa County’s Adaptive Traffic Signal Control Technology]
Investing in Smarter Infrastructure
Adaptive traffic signals offer a strategic advantage as cities and state DOTs continue to embrace smart infrastructure and future-ready systems. Their ability to respond in real time and optimize network-wide performance makes them a cornerstone of Intelligent Transportation Systems (ITS), innovative technologies that transportation planners leverage daily.
At Gorove Slade, we have extensive experience with traffic signal design, both at the preliminary and final plan development stages. Our design and analysis teams work hand in hand to remain current on the latest advances in traffic control strategies and technology.
