California Department of Transportation

Project Development Workflow Tasks (PDWT)

Part 3 - Identify Project Need and Project Initiation Document

II. Project Initiation Document

B. Develop Initial Alternatives (150.10) - Develop Concept Alternatives (WBS 150.10.15)

P49. Request Signal Warrants

Installation (or modification) of a traffic signal at an intersection originates from warrants established in the Traffic Manual and in the Manual On Uniform Traffic Control Devices published by the Federal Highway Administration (FHWA). The various Traffic Signal Warrants include:

  • Minimum Vehicular Volume
  • Interruption of Continuous Traffic
  • Minimum Pedestrian Volume
  • School Areas
  • Progressive Movement
  • Accident Experience
  • Systems Warrant
  • Combination of Warrants
  • Four Hour Volume Warrant
  • Peak Hour Delay Warrant
  • Peak Hour Volume Warrant
  • Bicycle Warrant (for bicycle signals).

However, the decision to install a signal should not be based solely upon the warrants, since a stop sign may resolve the problem and traffic signals may increase certain types of collisions. In order to justify the traffic signal, delay, congestion, approach conditions, driver confusion, future land use or other need for right of way assignment must be demonstrated. When a decision to install a signal is made, the project engineer should consider the need to widen the intersection. Additional widening may substantially increase project cost and lengthen delivery schedule, plus have greater impacts to the environment and right of way. Signal installation without widening for addition of turn lanes results in lengthy signal phasing and less efficient traffic movement through the intersection.

To obtain signal warrants, the project engineer must submit a request for a Signal Warrant study and/or Signal and Lighting cost estimates to the District Traffic Electrical Engineer. The project engineer should provide all available information pertinent to proposed signal location including; proposed project layout, As-Built records, traffic counts, turn movements, accident history, truck volumes and movements, pedestrian and bicycle usage, and locations of any nearby business or residential driveways. Photos of the project location are helpful.


Traffic Manual, (Chapter 9, “Traffic Signals and Lighting”)

US Department of Transportation Manual on Uniform Traffic Control Devices

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This page last updated October 20, 2010