Connecticut laws/regulations;

OLR Research Report

February 24, 2003




By: George Coppolo, Chief Attorney

James Fazzalaro, Principal Analyst

You asked if there is a state requirement for the duration of the yellow signal in traffic lights.


State law gives the State Traffic Commission the authority to establish standards for traffic lights. It also authorizes the commission to approve or disapprove the placement and operation of every traffic signal device. Pursuant to its statutory authority, the commission has adopted regulations including a specific regulation relating to traffic light intervals. This regulation specifies that yellow light change intervals should have a range of three to six seconds. This standard is the same as is contained in federal regulations.


CGS 14-298 establishes the State Traffic Commission within the Department of Transportation (DOT). It consists of the commissioners of Public Safety, Transportation, and Motor Vehicles. The law requires the commission, for the purpose of standardization and uniformity, to adopt and to publish regulations establishing a uniform system of traffic control signals, devices, signs, and markings consistent with state law for use upon the public highways.

CGS 14-299 provides that for purposes of standardization and uniformity, no installation of any traffic control signal light may be made by any town, city, or borough until it has been approved by the State Traffic Commission. The approval must be based on the necessity for, location of, and type of signal light. An application for approval must be submitted to the State Traffic Commission by the local traffic authority having jurisdiction. The commission may revoke any approval it has granted for signal lights at any times it deems it necessary for public safety.

Pursuant to the statutory authority, the State Traffic Commission adopted a regulation relating to yellow light change intervals ( 14-298-713, Regulations of Connecticut State Agencies). A portion of this regulation provides “yellow vehicle change intervals should have a range of three to six seconds.” This three- to six-second interval requirement mirrors the requirements and guidelines in federal law.


Pursuant to federal statutory and regulatory requirements, the federal highway administrator of the U.S. Department of Transportation adopted the Manual On Uniform Traffic Control Devices (23 USCA 109(d), 114(a), 217, 315, and 402(a); 22 CFR 655, and 49 CFR 1.48 (b)(8), 1.48 (b)(33), and 1.48(c)(2)). The manual defines traffic control devices as all signs, signals, markings, and other devices used to regulate, warn, or guide traffic, placed on, over, or adjacent to a street, highway, pedestrian facility, or bikeway by authority of a public agency having jurisdiction. The manual is incorporated by reference in 23 CFR, Part 655, subpart f, and is recognized as the national standard for traffic control devices on all public roads open to travel in accordance with 23 USCA 109(d) and 402(a).

In this manual the U.S. Secretary of Transportation, under authority granted by the Highway Safety Act of 1966, decreed that traffic control devices on all streets and highways open to public travel in each state must be in substantial conformance with the standards issued and endorsed by the Federal Highway Administration.

Yellow Change Intervals

The manual contains a specific standard relating to yellow change clearance intervals. Section 4 D.10 establishes the standard as: “a yellow signal indication must be displayed following every circular green or green arrow signal indication. The exclusive function of the yellow change interval is to warn traffic of an impending change in the right of way assignment. The duration of yellow change interval must be predetermined.” The manual specifies that a standard is a statement of required, mandatory, or specifically prohibited practice regarding a traffic control device.

The manual contains guidance in connection with this standard. The guidance specifies a yellow change interval should have a duration of approximately three to six seconds and that the longer intervals should be reserved for higher speed approaches. A guidance is a statement of recommended, but not mandatory, practice, in typical situations, with deviations allowed if engineering judgment or engineering study indicates the deviation to be appropriate.


The state DOT publishes a manual on traffic control signal design, which incorporates the requirements of the State Traffic Commission's regulations and standards and the standards contained in the federal Manual on Uniform Traffic Control Devices. The state design manual contains specific guidelines for traffic engineers to use when determining the precise clearance interval for yellow clearance lights. We have enclosed page 27 of the manual which specifies the formula that traffic engineers are to use in determining the precise duration of a yellow light at a particular intersection.