Traffic Signal Timing & Operations Strategies
The primary goal of traffic signal timing is to maintain the safe and efficient transfer of right-of-way between complementary and competing traffic demands at intersections. Traffic signal controllers are specialized devices designed to manage the flow of traffic at intersections by distributing capacity in the form of green time to each intersection approach. Signal timing is typically designed, implemented and maintained by the agency with operational authority over the intersection. The responsibility for traffic signal operation and maintenance generally falls to the state, county, city or local agency with jurisdictional authority over the physical location of the intersection; variations to this rule of thumb exists. At a minimum the design and operation of signalized intersection must consider the geometry of the intersection, lane configuration, and location of signal displays, vehicle and pedestrian demands, type and location of detection devices and the configuration of the transportation network.
The Highway Capacity Manual and Manual on Uniform Traffic Control Devices are primary references for professionals that design, implement and maintain traffic signal timing. The FHWA Traffic Signal Timing Manual represents a synthesis of best practice to guide the design, implementation and maintenance of traffic signal timing. Signal timing should be consistent with the operational objectives and policies that satisfy both the local and regional needs of all system users. Agencies responsible for the operation of traffic signals should proactively monitor performance to ensure that operational objectives are being met and are consistent with traffic demands, agency capabilities and resources. The National Traffic Operations Coalition (NTOC) National Traffic Signal Report Card provides a national assessment of how effectively agency programs are supporting the operation and maintenance of traffic signals.
Traffic signal operations strategies can be placed into two broad categories: Isolated or Coordinated. Isolated signal timing is generally designed to minimize delay at the intersections that are not in close proximity to other traffic signals. Coordinated operations strategies promote the smooth flow of traffic between along an arterial to minimize stops, avoid congestion, fuel consumption and air quality impacts resulting from the acceleration and idling of vehicles. Operational strategies consistent with the objectives of coordination include Adaptive Signal Control Technology (ASCT) and Traffic Responsive. The use of Systems Engineering is recommended (required when federal aid funds are used) to address the risks associated with the implementation of ASCT. Guidance and technical assistance is available to assist agencies with the application of Systems Engineering to the implementation of advanced signal operations strategies.
- Measures of Effectiveness and Validation Guidance for Adaptive Signal Control Technologies (HTML, PDF 10.2MB) (Publication Number: FHWA-HOP-13-031) - This report documents the tools and methodology developed for validation of ASCT systems and summarizes the testing of this approach and measures at a field site. The intent of the field study was not to evaluate the field site specifically but rather to demonstrate the application of the validation measures and methodology to a real world implementation of ASCT.
- Model Systems Engineering Documents for Adaptive Signal Control Technology (ASCT) Systems (HTML, PDF 1.2MB) (Publication Number: FHWA-HOP-11-027) - This document helps agencies to address the risks associated with ASCT implementation. The process involves exploration of the agencies needs and facilitates the development of requirements to facilitate the procurement of ASCT.
- Signal Timing Under Saturated Conditions (HTML, PDF 1.6MB) (Publication Number: FHWA-HOP-09-008) - This document helps agencies to address the risks associated with ASCT implementation. The process involves exploration of agency operations needs to develop requirements that facilitate the procurement of ASCT.
- Traffic Signal Timing Manual (HTML, PDF 8.4MB) (Publication Number: FHWA-HOP-08-024) - A comprehensive synthesis of traffic signal timing design and operational concepts.
- Traffic Signal Timing On a Shoestring (HTML, PDF 1MB) (Publication Number: FHWA-HOP-07-006) - This effort documents the minimum amount of data collection and optimization that should be performed in a signal retiming to acquire some appreciable benefits. This is aimed at jurisdiction or municipalities that cannot afford to perform more extensive data collection and analysis.
- Traffic Signal Timing Process (HTML, DOC 458KMB) - This report identifies the steps that are required to time traffic signals and activities that result in improved traffic signal timing.
- Highway Capacity Manual 2010 - Describes and provides methodology to assess the traffic and environmental effects of highway projects.
- Additional Publications
- Traffic Signal Design and Operation - NHI Course #133121 - This course addresses the application of the Manual of Uniform Traffic Control Devices (MUTCD) to intersection displays, as well as signal timing, computerized traffic signal systems, control strategies, integrated systems, traffic control simulation and optimization software. The course is divided into two primary parts: Traffic Signal Timing and Design, and Traffic Signal Systems.
- Mobile Hands on Signal Timing Training (MOST) – A Hands on Approach to Signal Timing Education - MOST uses a simulation environment to let you directly observe how the signal timing parameters that you select affect the quality of traffic operations at a signalized intersection. Unlike traditional courses that emphasize an instructor-focus (with lectures presented to students), the MOST course emphasizes a student focus in which you will learn by doing experiments, analyzing data that you collect, and drawing conclusions about what makes good signal timing practice.
- Additional Training