---
title: "Traffic Signal"
url: "https://commonwaysystem.org/patterns/elements/traffic-signal/"
id: "ELM-TFS-14"
description: "A signal-controlled device using red, yellow, and green indications to assign right-of-way among conflicting vehicle movements at an intersection."
updated: "2026-09-26"
---

# Traffic Signal

`ELM-TFS-14`

Situational / Discouraged Element

Traffic Signal

A signal-controlled device using red, yellow, and green indications to assign right-of-way among conflicting vehicle movements at an intersection.

## Related Media

The items below come from outside the Commonway System, external videos, podcasts, and articles related to this page's topic, not part of the guidebook itself.

Aligned

### [Why the Dutch Wait Less at Traffic Lights](https://www.youtube.com/watch?v=knbVWXzL4-4)

Not Just Bikes

Breaks down Dutch traffic-responsive signal timing, independent phasing, transit signal priority, and no-right-turn-on-red as a pedestrian/cyclist safety measure.

Aligned

### [Crossing the Street Shouldn't Be Deadly (but it is)](https://www.youtube.com/watch?v=_ByEBjf9ktY)

Not Just Bikes

This video walks through pedestrian crossing designs, from beg buttons and signal phases to raised crossings, HAWK beacons, and continuous sidewalks. It shows how crossing geometry and timing decide whether walking is safe, the same question behind the Commonway System's crosswalk and crossing elements.

## Why this pattern exists

Above a certain volume or conflict complexity, an uncontrolled or sign-controlled intersection can no longer safely and efficiently sort competing movements; a traffic signal imposes timed, positive control over who moves when. This pattern exists to document signal use as a documented departure from Commonway System’s roundabout-default intersection treatment, requiring its own justification.

## Key considerations

-   Consistent with Commonway System’s intersection defaults, signal installation should require documented burden-of-proof justification rather than being a default choice[1]
-   Timing and phasing should account for all modes present, not just vehicle throughput; pedestrian and bicycle phases need adequate crossing time
-   Signal coordination along a corridor affects speed and platooning behavior well beyond the single intersection where it is installed

## Related patterns

[Roundabout](https://commonwaysystem.org/patterns/intersections/roundabout.md) (INT-RAB-01) (the CS default this pattern is a documented departure from); [Pedestrian Signal](https://commonwaysystem.org/patterns/elements/pedestrian-signal.md) (ELM-PDS-15), [Bicycle Signal](https://commonwaysystem.org/patterns/elements/bicycle-signal.md) (ELM-BCS-16) (companion signal types at a signalized intersection)

## References

1.  Legal / regulatory [MUTCD 11th Edition with Revision 1 (FHWA, December 2025; effective March 5, 2026), Chapter 4C, "Traffic Control Signal Needs Studies." Establishes the nine signal warrants, and explicitly states that meeting a warrant does not itself require installation.](https://mutcd.fhwa.dot.gov/pdfs/11th_Editionr1/mutcd11theditionr1hl.pdf)