The Signal Warrant Calculator is a planning-level tool designed to assist in the initial screening of whether a traffic signal may be warranted at an intersection. It helps planners and engineers identify intersections that might benefit from further study based on traffic volumes during peak periods.
This tool is particularly useful in the early stages of transportation planning, land development, or functional design studies where quick operational assessments are needed. It is not intended to replace a full traffic signal warrant study but rather to guide decisions about whether further analysis should be considered.
Methodology Overview
The calculator is based on the Highway Capacity Manual (HCM) and the Ontario Traffic Manual Book 12 methodologies for traffic signal justification, specifically:
- Justification 1 – Minimum Vehicular Volume:
Evaluates whether the combined volume of vehicles on major and minor approaches meets or exceeds defined thresholds over an 8-hour or peak hour period. Subcategories:- 1A: Total intersection volume
- 1B: Minor road volume
- Justification 2 – Delay to Cross Traffic (Minor Road Delay):
Assesses potential delays to vehicles on the minor street due to conflicting traffic on the major road. Subcategories:- 2A: Major approach volume
- 2B: Combined volume of conflicting turns and minor street through traffic
Compliance percentages are calculated for each sub-warrant. Signalization is generally considered if:
- Both components of either justification (e.g., 1A and 1B) meet 100% of the requirement, or
- Both Justification 1 and 2 achieve at least 80% compliance.
This rapid evaluation tool helps prioritize intersections for more detailed operational or safety analysis.
These justifications are only two of several warrant types typically examined in a full signal warrant study.
Signal Warrant Calculator
Disclaimer
- This tool is provided for reference and planning purposes only and does not constitute a formal signal warrant analysis.
- Results are based on user inputs and simplified methodologies. Engineering judgement must always be applied.
- Accurate results require verified data, including field counts and site-specific characteristics.
- Arterials and its developers accept no liability for the use of this tool or for any actions taken based on its results.
- This tool does not replace the requirements of the HCM, OTM Book 12, or municipal warrant guidelines.
- A full warrant study should be conducted by a licensed transportation professional using proper procedures and supporting data.
Important Notes
This calculator uses only peak hour vehicle volumes. A comprehensive signal warrant analysis normally requires:
- 8-hour and/or 4-hour volume counts
- Pedestrian crossing volumes
- Collision history
- Field observations and geometric assessments
Without these inputs, this tool cannot fully determine warrant compliance—it serves as an operational volume screening only.
Need More Help?
For formal traffic studies, detailed warrant assessments, or questions about how to interpret the results of this tool, please contact Arterials. Our team offers professional traffic engineering services, including traffic operations analysis, warrant studies, and signal design.