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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations

This brochure is an archived publication and may contain dated technical, contact, and link information
Publication Number: FHWA-HRT-06-083
Date: January 2006

ACS Lite

traffic signal graphic

A significant portion of traffic delays in metropolitan areas are caused by poor traffic signal timing. ACS Lite, a reduced-scale version of the Federal Highway Administration’s (FHWA) Adaptive Control Software (ACS), offers small and medium-size communities a low-cost traffic control system that operates in real time, adjusting signal timing to accommodate changing traffic patterns and ease traffic congestion. ACS Lite can be used with new signals or to retrofit existing traffic signals. It is designed for closed-loop systems, providing cycle-by-cycle control.

ACS Lite was developed by FHWA, in partnership with Siemens, Purdue University, and the University of Arizona.

How Does It Work?

The ACS Lite software continuously monitors traffic signals and the flow of traffic, and adjusts signal timing accordingly. These adjustments can be made on a user-specified time frame. ACS Lite can be used in closed-loop systems, with no need for a central computer system, since the software resides on a field-hardened CPU and is located at a local traffic signal controller cabinet. The software can be deployed using as few as two traffic detectors on a roadway. Once deployed, the system is ready to go and does not require periodic calibration.

Traffic signal with a traffic detector mounted on the signal arm.


The benefits of using ACS Lite include:

  • Helps ease traffic congestion.
  • Widely deployable.
  • Low cost design.
  • Works with closed-loop systems.
  • Operates in real time.
  • Does not require calibration.

Real-World Use

ACS Lite has been demonstrated in Gahanna, Ohio; Houston, Texas; and Bradenton, Florida. The last field test is planned for El Cajon, California. All of the test sites showed improvement in traffic flow.

How Can I Obtain ACS Lite?

ACS Lite is available from the following vendors: Eagle, Econolite, McCain, Peek, and Siemens. The software was designed to work with these brands of traffic signal systems. A locality currently using a Peek system should contact Peek, for example, while one using Eagle should contact Eagle, and so forth. For contact information, see list at the end of this brochure.


For more information about ACS Lite, contact Raj Ghaman, Travel Management Team Leader in FHWA’s Office of Operations Research & Development, 202-493-3270 (e-mail: raj.ghaman@dot.gov).

traffic signal controller cabinet

To obtain a copy of ACS Lite, contact one of the following vendors:

Mark Hudgins, 512-837-8429 (e-mail: mark.hudgins@itssiemens.com)

Gary Duncan, 714-630-3700 (e-mail: gduncan@econolite.com)

Steve Brown, 760-784-8582 (e-mail: sbrown@mccaintraffic.com)

Peter Ragsdale, 562-923-9600, ext. 177 (e-mail: pragsdale@quixotecorp.com)

Steve Shelby, 520-290-8006, ext. 115 (e-mail: steve.shelby@itssiemens.com)

Additional Contacts:

Purdue University
Darcy Bullock, 765-494-2226 (e-mail: darcy@purdue.edu)

University of Arizona
Larry Head, 520-621-2264 (e-mail: Larry@sie.arizona.edu)


This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this brochure only because they are considered essential to the objective of the document.

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