U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000


Skip to content U.S. Department of Transportation/Federal Highway AdministrationU.S. Department of Transportation/Federal Highway Administration

Accelerating Innovation

FHWA Home / Accelerating Innovation / Every Day Counts / Adaptive Signal Control

Adaptive Signal Control

Case Studies

Traffic signal timing that does not keep pace with variability in traffic demand contributes to congestion, delays, increased fuel consumption and excess emissions. Adaptive Signal Control Technology (ASCT) addresses variability by continuously monitoring traffic conditions, evaluating performance and updating signal timing to promote smooth traffic flow and equitably distribute green time to each intersection approach. Developed in the late 1980s, ASCT has been widely deployed internationally but has seen limited implementation in the United States.

Below are case studies showing the successful application of adaptive signal control technologies in the United States and Canada.

State Route 100, Upper Uwchlan Township, PA

Background

In September of 2012, Upper Uwchlan Township, Pennsylvania selected and deployed an Adaptive Signal Control Technology (ASCT) developed by Econolite Control Products, Inc. Centracs Adaptive was deployed at nine intersections along State Route 100 and Graphite Mine Road. The arterials serve approximately 50,000 vehicles per day and experienced heavy traffic congestion during the peak hours. Upper Uwchlan selected this ASCT with the goal of maximizing progression along these complicated arterials, while adequately serving side street demand to minimize total network delay.

Benefits

After implementing this ASCT, Upper Uwchlan reported significantly improved traffic conditions from increased progression in both directions. Motorists have noticed the benefits of the ASCT and have provided feedback expressing their gratitude for the improvements experienced on their daily commutes. The Township has been extremely pleased with the ASCT and has reported the system to be very reliable in all traffic conditions. In addition, local engineers appreciate that they have full control and access to the system, and are able to monitor it with regularity using both an in-house workstation and/or a remote VPN connection. The Township Manager reported that the ASCT was a great tool during Hurricane Sandy, allowing engineers to monitor the signal system as a whole from the emergency operations center.

Learn More

This ASCT was developed with the goal of minimizing total network delay. The system works by first analyzing each intersection individually, and balancing the green time between under-utilized and over-utilized phases. Once each intersection has been individually optimized, the ASCT looks at the signal system as a whole and adjusts the offsets to maximize progression. In addition to improving traffic flow, this ASCT aims to simplify operation by directly interfacing with the Advanced Transportation Management System (ATMS). This allows traffic engineers to monitor their adaptive corridors, as well as the rest of the signal system, in one centralized location.

Victory Boulevard, Staten Island, New York

Background

In May 2010, New York City Department of Transportation (NYCDOT) implemented an Adaptive Signal Control Technology (ASCT), developed by KLD Associates, Inc in collaboration with Transcore, called Adaptive Control Decision Support System (ACDSS) on 4 intersections along Victory Boulevard, Staten Island. The site includes a critical intersection at the entrance to the College of Staten Island, and the connecting ramps to/from the Staten Island Expressway (I-278). Traffic patterns on this corridor feature predominantly east-west commuting demand with daily variations caused by the heavy traffic into and out of the college.

The system allows autonomous and "operator-in-loop" modes. Under autonomous operation, cycle length, offset, and splits are optimized periodically based on real time traffic predictions. In the "Operator-in-loop" mode an operator can interact with the real time system by looking at the just-in-time traffic simulation, reviewing and validating the recommended plans before implementing them in the field.

Benefits

The implementation of this ASCT was able to address the variable traffic demands along the implementation site. The highly variable left-turn traffic demand into the college is better serviced without compromising other approaches and the overall traffic is running smoother and is less congested.

Learn More

This ASCT can optimize linear arterial signals to promote smooth flow as well as grid networks. It requires midblock detection that provides volume and occupancy data. The system can also utilize travel-time data to optimize signals if that data is available. The system supports user defined constraints for variables (split, cycle, offset), the ability to selectively optimize the variables (for example, split only), and the frequency of updates (for example, cycle length every 20 cycles, split every cycle). Through a web service interface, the ACDSS system works with any NTCIP compatible controller.

Disclaimer: Reference in this site to any specific commercial product, process, or service, or the use of any manufacturer, trade, firm or corporation name is for the information and convenience of the public, and does not constitute endorsement, recommendation, or favoring by the Federal Highway Administration.

City of Tyler, TX

Background

The City of Tyler Texas conducted a public survey of its citizens in 2006 to identify the most important issues that the City of Tyler should address. Traffic congestion was rated as the most important issue with safety and maintaining low tax rates rating second and third. As a result, the City of Tyler formed a special Traffic Congestion Committee to explore and evaluate alternatives to reduce congestion. The Committee identified Adaptive Signal Control Technology (ASCT) as a potentially useful tool. The City selected Siemens to implement an adaptive control technology called ACSLite. This ASCT is relatively economical and fit well with Tyler’s previous infrastructure investments and limited resources for operation and maintenance of traffic signals.

This ASCT is one of four adaptive control algorithms developed through a research effort that began in 1992, sponsored by the FHWA Turner Fairbank Highway Research Center. It monitors traffic conditions and updates signal timing parameters to promote smooth traffic flow and equitable distribution of green light time within the context of the signal timing requirements designed by agency professionals. The City of Tyler implemented the ASCT on 16 intersections clustered around a particular busy part of town where South Broadway Avenue crosses Loop 323. This is a growing area that includes a large shopping mall, several big box stores, and a high school. The project included upgrades to signal control equipment, detection and communication systems.

Benefits

The implementation of ASCT allowed the City of Tyler to address the highly variable traffic demands of the area. Before and after studies measured substantial reductions in delay, stops, and travel time during both weekday and weekend traffic. Citizen complaints have been significantly reduced; traffic signal operations have shifted from a reactive mode of operation to a proactive mode that allows the agency to manage the performance of the system. The City of Tyler has achieved a higher level of performance using its existing staff and has reduced resources committed to data collection necessary to retime the corridor.

Learn More

The City of Tyler is currently expanding it use of ASCT to incorporate signals along the eastern and western sections of the city’s Loop 323 roadway. The system can be deployed in a central system or closed-loop configuration. This ASCT has also been deployed in Anne Arundel County, MD and Pickerington, OH.

Disclaimer: Reference in this site to any specific commercial product, process, or service, or the use of any manufacturer, trade, firm or corporation name is for the information and convenience of the public, and does not constitute endorsement, recommendation, or favoring by the Federal Highway Administration.

City of Temecula

Background

One of Southern California’s popular communities, the City of Temecula experienced a population increase of more than 50% over the past decade. The rapid expansion caused congestion throughout the city’s major arterials that connect residential communities, commercial districts and the freeway. To reduce commute times and harmful vehicle emissions, and to improve quality of life for residents, city traffic engineers turned to an Adaptive Signal Control Technology (ASCT) developed by McCain Traffic called QuicTrac.

The City of Temecula selected this ASCT because of its ability to meet project objectives, including compatibility with existing infrastructure, and ease of installation and maintenance. The software was deployed at 83 intersections, including 7 Caltrans’ signals, spanning 18 miles of roadway.

Benefits

The City of Temecula was able to successfully achieve project goals of improving quality of life for residents by reducing commute times and smog producing vehicle emissions. With a benefit-to-cost ratio of 30:1, the system succeeded in offering a maximum benefit to the public at a minimal cost. Though results varied on an arterial-by-arterial basis, citywide the system showed a 14% reduction in travel time, a 17% increase in corridor speed, and a 29% reduction in stops. Moreover, the City was able to reduce queuing on freeways by establishing communication with Caltrans’ signals at freeway ramps. The estimated savings for commuters from these changes is estimated at an annual sum of $2.6 million in travel time and $437,000 in fuel costs.

Learn More

This ASCT was developed to deliver real-time, progressive traffic control that is easy to setup and maintain, and is cost-effective. It utilizes an algorithm to calculate optimum cycle length, splits and offsets along the entire corridor to expedite traffic flow. It is compatible with a range of traffic controller configurations, including 170 controllers, has relatively minimal detector requirements, and supports a variety of communication protocols.

Disclaimer: Reference in this site to any specific commercial product, process, or service, or the use of any manufacturer, trade, firm or corporation name is for the information and convenience of the public, and does not constitute endorsement, recommendation, or favoring by the Federal Highway Administration.

City of Salinas, CA

Background

In February 2011, the City of Salinas, CA implemented an Adaptive Signal Control Technology developed by Rhythm Engineering called InSync. The ASCT was installed on 5 intersections along Main Street with the objective of reducing travel time, delay, fuel consumption, vehicle emissions and stops along the corridor. The land use on Main Street includes a sports arena, shopping centers, parks and other recreational facilities that create variability during special events, off-peak hours and weekends. The City of Salinas selected this ASCT due to its compatibility with existing controllers, use of video detection and ease of operations.

Benefits

After the implementation of ASCT, travel time and delay on the corridor were noticeably reduced. An independent engineering firm study shows the ASCT reduced travel times in all time periods by 37% to 46% and delivers a benefit of $6,887 to motorists each week day. The City of Salinas is now in the process of expanding the system to other critical corridors.

Learn More

The City of Salinas has one traffic engineer and contracts the maintenance of traffic signals to a private contractor; given these constraints, a system that was easy to operate and maintain was highly desired. This ASCT implements two specific strategies to improve traffic signal operations. The first focuses on maximizing the utilization of green light time for all intersection approaches so that vehicles see green signals more often. The second strategy maximizes the number of green signals vehicles receive as they drive through multiple intersections.

Disclaimer: Reference in this site to any specific commercial product, process, or service, or the use of any manufacturer, trade, firm or corporation name is for the information and convenience of the public, and does not constitute endorsement, recommendation, or favoring by the Federal Highway Administration.

York Region, Greater Toronto, Canada

Background

The Region of York is a fast growing municipality in the Greater Toronto area, and is expected to continue to experience rapid growth for the foreseeable future. This rapid growth has already strained the York Region’s signal system, and there is a growing need for an innovative, cost-effective method to efficiently manage the rising traffic demand. To address this need, York Region deployed and evaluated an Adaptive Signal Control Technology developed by Delcan Corporation called Multiple-Criteria Adaptive Control (MAC) System as an enhancement to their existing Centralized Traffic Control System. The project, which was a test pilot of ASCT for a group of 11 signalized intersections along a major arterial street, was a public-private-partnership between Delcan Corporation and the Regional and Federal governments in Toronto, Canada.

Benefits

The pilot system implementation demonstrated that an open system architecture design and multi-protocol communications interface allow an ASCT to be integrated with an existing central traffic signal system and legacy traffic signal controllers. The system addressed variable traffic conditions within the pilot site from light to nearly saturated traffic, over-saturated, and gridlocked conditions.

As part of the before and after studies, the pilot network was first optimized manually before the ASCT was implemented. The field comparison conducted during the AM peak period demonstrated that the system performed as well as the best optimized pre-timed signal timing plan. This was a positive result in that recently optimized pre-timed plans represent the “best case” scenario, and over time, adaptive control will continuously adjust to changes in traffic volumes and flows; whereas the pre-defined timing plans will steadily erode. In addition, it was observed that the green split provided by the system tracks the intersection volume split closely while the cycle length tracks the total volume up to the maximum specified cycle length, further indicating that the system adapts to the traffic trend effectively.

Learn More

The open system architecture and multi-protocol communications interface allow for the seamless integration of this ASCT package with legacy traffic signal management systems and traffic signal controllers. The communications scheme supports a variety of wireless technologies. The evaluation of the ASCT was first carried out by hardware-in-the-loop micro-simulation, which indicated that significant reductions of delays and queue lengths and increases in volume throughput could be achieved.

Disclaimer: Reference in this site to any specific commercial product, process, or service, or the use of any manufacturer, trade, firm or corporation name is for the information and convenience of the public, and does not constitute endorsement, recommendation, or favoring by the Federal Highway Administration.

Highway 99W Oregon

Background

The Oregon Department of Transportation (ODOT) undertook a major retiming project along a congested portion of Highway 99W. The project involved a suburban corridor 4.25 miles in length and included 21 signalized intersections with an Average Daily Taffic (ADT) volume of 50,000. The cross section varies along the length, but is typically 5 vehicle lanes with a center two-way left turn lane. ODOT chose to deploy an Adaptive Signal Control Technology (ASCT) called NWSVoyage, developed by Northwest Signal. NWSVoyage was developed by traffic engineers in Portland, OR. Its adaptive algorithms are concerned with optimizing capacity on a cycle-by-cycle basis, in a highly reactive manner.

Benefits

The objective of the project was to manage congestion on Highway 99W by improving the utilization of green light time. The algorithms were already included in the NWSVoyage controller application firmware in use by ODOT, facilitating a low cost solution that was manageable and presented a short learning curve for support staff. After activating the algorithms ODOT support staff was able to receive immediate feedback on how the algorithms were impacting the operation of each intersection. No elaborate communication or detection infrastructure was required to implement the algorithms.

Learn More

This ASCT works with the philosophy that a traditional coordination plan, if well developed and properly implemented is the primary element in resolving corridor congestion. With the traffic simulation tools available today and with the reporting available from traffic controllers themselves, it is relatively easy to deploy a first rate coordination plan that handles normal daily traffic very well. What is lacking, however, is the ability to quickly respond to random traffic fluctuations. This ASCT offers a set of powerful, inexpensive adaptive functions could be developed that would "overlay" over the top of a well designed coordination plan.

The ASCT uses two algorithms that use advance detectors to optimize capacity and to determine the lead/lag pattern of the upcoming phase pair. It functions on the tried and true signal timing principle that the heavier phase movement should LAG in order to benefit from time given up by a gap out of the leading phase.

Disclaimer:Reference in this site to any specific commercial product, process, or service, or the use of any manufacturer, trade, firm or corporation name is for the information and convenience of the public, and does not constitute endorsement, recommendation, or favoring by the Federal Highway Administration.

U.S. Route 19, Florida

Background

US Route 19 is the most heavily traveled signalized corridor in Pinellas County. The corridor includes the spring training facilities for a Major League Baseball team and is lined with retail land use. The corridor carries heavy daily commuter and seasonal tourist traffic due to its proximity to the Gulf of Mexico and Tampa Bay. In 2003, the Florida Department of Transportation (FDOT) implemented an Adaptive Signal Control Technology called OPAC on 16 miles of US Route 19 at 15 intersections. The system was deployed by Telvent USA Corporation, formerly PB Farradyne.

Benefits

FDOT conducted an independent evaluation of the system’s performance. The study showed significant reductions in travel time, with up to 25% reductions in travel time in the peak directions during the AM and PM peak periods. Additionally, using roadside environmental sensors, FDOT found significant improvement in air quality parameters with up to 11% in carbon monoxide and 17% in fine particulates have been achieved when controllers were running OPAC as compared to time based mode of operation. Since the original deployment, the operating agency, Pinellas County Public Works, has expanded the system to include 36 intersections on two other critical county routes and plans further expansions.

Learn More

This ASCT is designed to provide a distributed control strategy featuring a dynamic optimization algorithm that calculates signal timing to minimize the performance function of total intersection delay and stops. The system evaluates traffic flow parameters at each intersection every cycle in real time and adapts to fluctuating traffic conditions through its optimization algorithm. Splits are re-calculated every few seconds while offsets are adjusted every cycle. The background cycle length is updated at a user-specified frequency while the actual cycle length may vary from cycle to cycle based on actual traffic demands. Together, these features allow the system to adapt to actual traffic volumes and conditions so that the traffic network operation is optimized.

The underlying traffic simulation and timing optimization algorithms in this ASCT are an outcome of a research effort that began in 1992 by the FHWA Turner Fairbank Highway Research Center.

Disclaimer: Reference in this site to any specific commercial product, process, or service, or the use of any manufacturer, trade, firm or corporation name is for the information and convenience of the public, and does not constitute endorsement, recommendation, or favoring by the Federal Highway Administration.

Pinellas County, Florida

Background

Pinellas County, Florida, located in the Tampa Bay region, is the most densely populated county in the state and, like other major urbanized metropolitan areas, has critical transportation problems. A lack of limited access highways and severe seasonal tourism variations compound these problems and place a heavier burden on the surface transportation network than in other urbanized areas. To better manage existing facilities, Pinellas County, in conjunction with the Florida Department of Transportation (FDOT) and the City of Clearwater, formed an ITS Committee to develop a, phased program to deploy Adaptive Signal Control Technology (ASCT) on congested arterials that could not be physically expanded and experience high seasonal traffic fluctuations.

After a careful review of the available systems, the ITS Committee selected RHODES, available from the Arizona State University as the most suitable ASCT for implementation along the State Route 60 Corridor, a six-lane divided arterial with 17 closely-spaced signals and an Average Annual Daily Traffic (AADT) of 60,000 vehicles/day that experiences significant fluctuations in demand.

Benefits

A comprehensive evaluation of the ASCT showed significant operational improvements along the main corridor, with minimal impact to side-street traffic. An overall consistent reduction in travel time for all time periods ranging from 5-15%, along with reductions in stops (10-24%) and delays (9-39%). Total lifecycle savings for the project (including the ASCT and all other ITS improvements) over a 10-year period were estimated at nearly $10.6 million with a benefit/cost ratio of 7.75. Other anecdotal benefits were observed such as better progression, less apparent congestion and fewer inappropriate driving behaviors, such as red light running and erratic lane changing. As a result of its work deploying its "Countywide ATMS Adaptive Signal System", the Institute of Transportation Engineers awarded Pinellas County its Transportation Achievement Award in 2007.

Learn More

This ASCT is one of three adaptive control algorithms resulting from a 10-year research effort that began in 1992 by the FHWA Turner Fairbank Highway Research Center and Arizona Department of Transportation’s (ADOT) ATRC Program. The objective of the research was to develop Adaptive Control Software (ACS) suitable for US infrastructure and traffic conditions and to demonstrate these systems in several locations throughout North America. The system optimizes the real-time performance of a corridor or network by proactively responding to the natural stochastic variations in traffic flow and setting the durations of phases accordingly. This ASCT sets phase durations explicitly, rather than through timing parameters such as splits, cycle lengths and offsets, enabling "proactive response."

The system can operate in both distributed and centralized architectures on multiple operating systems and has operated in a variety of networks. The software continues to be enhanced, as new research and field improvements are incorporated.

Disclaimer: Reference in this site to any specific commercial product, process, or service, or the use of any manufacturer, trade, firm or corporation name is for the information and convenience of the public, and does not constitute endorsement, recommendation, or favoring by the Federal Highway Administration.

City of Gresham, Oregon

Background

In response to its commitment to improve the operational efficiency of congested arterials the City of Gresham, Oregon conducted an evaluation of advanced traffic signal operations technologies. In 2007, the City of Gresham selected Transcore to implement an Adaptive Signal Control Technology (ASCT) called Sydney Coordinated Adaptive Traffic System (SCATS) on Burnside Road between Eastman Parkway and Powell Blvd. The ASCT enabled the city to achieve its objective of reducing congestion by allowing the traffic signal system to be more responsive to variability in demand that was difficult to account for with traditional signal timing methods.

Benefits

Average travel times on the Burnside Road corridor were reduced during both weekdays and weekends, the number of vehicles stopping at red lights and completing left turns after entering left turn pockets was significantly reduced. The agency maintains a total of 110 traffic signals with two engineers and three technicians; after a few weeks of training, the staff became proficient with the operations and maintenance of the ASCT. The system allows the agency to proactively operate the traffic signal system within the existing staffing level. Citizen complaints related to signal timing have shifted to compliments and a desire to see the strategy expanded to other parts of the city.

Learn More

A regional steering committee set a specific and measurable goal for the ASCT to provide a cost effective and reliable system. Ultimately the ASCT improved the performance of the existing system using the current capabilities of the operations staff able to meet both current and future needs. SCATS was developed and continues to be improved and maintained by the Roads and Traffic Authority of New South Wales.

Disclaimer:Reference in this site to any specific commercial product, process, or service, or the use of any manufacturer, trade, firm or corporation name is for the information and convenience of the public, and does not constitute endorsement, recommendation, or favoring by the Federal Highway Administration.

Orange County Florida – High Vehicle Density Special Events Congestion

Background

Orange County Florida is home to a dense cluster of theme parks, (Walt Disney World Resort, Universal Studios, Sea World) special events generators like the Orange County Convention Center and a host of restaurants, hotels, retail centers, residential and commercial areas that create unpredictable and variable traffic demands that challenge traditional methods of implementing traffic signal timing. To address the unpredictability and variability in traffic demand that results in congestion, reductions in safety, and excess delay and emissions, Orange County Florida selected Siemens to implement an Adaptive Signal Control Technology called SCOOT.

The ASCST was initially deployed on seven intersections in May of 2000, and is currently operating on 70 traffic signals. Two traffic engineers, three technicians and 15 maintenance staff operate and maintain a total of 560 traffic signals in Orange County; the ASCT allows the existing staff to proactively operate and maintain the signals where variability and unpredictability in demand create a traffic signal timing problem that were not easily addressed through traditional traffic signal timing methods.

Benefits

Orange County Florida was able to achieve its operational objective of network wide efficiency through them implementation and ongoing operation and maintenance of ASCT. Within the network, vehicles on the main arterial, on side-streets, and left-turners receive equitable green light time to minimize delays. Overall, the delay, fuel consumption and emissions within the network are optimized allowing the agency to effectively achieve operational objectives within the constraints of its operations and maintenance resources and staffing capability.

Learn More

The areas around universities have complex traffic patterns that are challenging to address with standard control systems. This ASCT is able to handle both Grid and corridor applications and has been deployed around three major universities in the United States: in Ann Arbor around the University of Michigan, in Orange County around the University of Central Florida, and in Minneapolis around the University of Minnesota. Each region has continued to expand the number of intersections under ASCT control.

Disclaimer:Reference in this site to any specific commercial product, process, or service, or the use of any manufacturer, trade, firm or corporation name is for the information and convenience of the public, and does not constitute endorsement, recommendation, or favoring by the Federal Highway Administration.

SR 436, Seminole County, Florida

Background

In May of 2011, Seminole County, Florida implemented an Adaptive Signal Control Technology (ASCT) developed by Trafficware, Ltd called SynchroGreen. The ASCT was installed at 12 intersections along SR 436 (Altamonte Drive) between Westmonte Drive and Maitland Avenue. This corridor has an Average Daily Traffic (ADT) of approximately 56,000 vehicles and experiences constant fluctuation in traffic due to surrounding commercial developments. Furthermore, traffic signal coordination on SR 436 is difficult due to heavy pedestrian activity, as well as frequent traffic signal pre-emption due to the proximity of a fire station and hospital.

Benefits

The SR 436 corridor provided a challenging setting to test the capabilities of ASCT. Improvements in travel time, arterial delay, stops and side street delay were observed. Noticeable improvements were observed on SR 436 after ASCT was deployed and Seminole County has experienced a drastic reduction in the number of phone calls regarding traffic signals and congestion on this corridor. In the future, ASCT will be expanded to other intersections on SR 436, as well as other areas of Seminole County.

Learn More

Seminole County wanted to install a system capable of using their preferred vehicle detection without adding any additional hardware to the signal cabinet. This ASCT provided a scalable solution minimizing the need for additional hardware by utilizing as much of the existing traffic signal infrastructure as possible. The systems algorithm not only considers the needs of arterial traffic, but also considers the needs of side streets and pedestrians. This ASCT offers the capability of functioning in a simulation environment allowing benefits to be estimated prior to deployment.

Disclaimer:Reference in this site to any specific commercial product, process, or service, or the use of any manufacturer, trade, firm or corporation name is for the information and convenience of the public, and does not constitute endorsement, recommendation, or favoring by the Federal Highway Administration.

Media

Page last modified on August 12, 2013.
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000