AC Group Template

Traffic Engineering Services

Traffic Signal Warrant Analysis

Traffic signal warrants define minimum thresholds for certain traffic and pedestrian operational conditions at an intersection, which if satisfied, may justify the installation of a traffic control signal. The eight Warrants evaluated when determining warranting conditions are defined in the Manual on Uniform Traffic Control Devices (MUTCD). The MUTCD also states that “the satisfaction of a warrant or warrants shall not in itself require the installation of a traffic control signal.”

The MUTCD recommends installation of a traffic signal only after the following conditions are met:

One or more of the factors contained in the eight warrants is met;
An engineering study shows that the traffic control signal will improve the overall operation and/or safety of the intersection; and
The traffic signal will not seriously disrupt progressive traffic flow.

Traffic Impact Analysis

A traffic impact analysis (TIA) is a traffic engineering study that assesses the potential traffic impacts of a proposed development on the surrounding roadway system. The TIA can be used to determine whether a development is appropriate for a specific site and to determine what type of transportation improvements may be necessary for the surrounding roadway system to support the development.

Generally, there are three scenarios considered when evaluating the traffic impacts associated with a proposed development. These scenarios include the existing conditions, the projected conditions, and the projected conditions with additional trips from the proposed development. The difference between the “projected” conditions and the “projected with development” conditions is considered the impact. Traffic simulation applications are typically used for this type of analysis.

Traffic Signal Design

The origin of traffic control signals can be traced back to the manually operated semaphores first used in London as early as 1868. The first electric signal in the United States was developed by James Hoge and installed in Cleveland, Ohio in 1914. By providing alternate right-of-way to various traffic movements, traffic signals exert a profound influence on traffic flow and can operate to the advantage or disadvantage of the vehicles or pedestrians they control.

The design of a traffic control signal considers the existing traffic volume, intersection layout, anticipated operations (i.e., phasing and timing), and pedestrian activity. The design of the traffic control signal includes equipment layout (e.g., pole and mast arm location, signal head requirements, etc.), controller location, detector use and placement, wiring of components, pedestrian signals, intersection pavement markings and traffic signal timing.