What Are Traffic Lights Considered?

They are considered traffic control devices—specifically, regulatory traffic signals that assign right-of-way and manage movements of vehicles, cyclists, and pedestrians at intersections and crossings. In law and engineering standards worldwide, traffic lights fall under the broader category of devices used to regulate, warn, and guide road users.

Formal Definition and Classification

Across major jurisdictions, traffic lights are formally defined as traffic control devices and more precisely as traffic signals. These definitions carry legal weight, determining how signals are designed, installed, operated, and enforced.

The list below outlines how leading standards bodies classify traffic lights.

• United States: The Manual on Uniform Traffic Control Devices (MUTCD), 11th Edition (issued December 2023; effective in 2024), defines traffic control devices as signs, signals, and markings placed by authority to regulate, warn, or guide traffic. “Highway traffic signals” are a distinct class within this framework and are used to assign right-of-way based on red, yellow, and green indications.
• United Kingdom: Under the Traffic Signs Regulations and General Directions (TSRGD) and the Road Traffic Regulation Act 1984, traffic lights are “traffic signals,” a prescribed form of “traffic sign,” and are legally enforceable indications controlling road users.
• International/UN: The 1968 Vienna Convention on Road Signs and Signals classifies traffic lights as “light signals” used by competent authorities to control traffic movements, standardizing meanings of steady and flashing colors.
• Australia and New Zealand: National road rules and traffic control device manuals define traffic signals as traffic control devices; standards specify design and operation, including pedestrian signals and accessibility features.
• Canada: Provincial laws and the Transportation Association of Canada’s guides treat traffic signals as traffic control devices, with uniform color meanings and warrant-based installation practices.

Taken together, these definitions converge on the same point: traffic lights are a regulated subset of traffic control devices, employed to allocate right-of-way and increase safety and efficiency at conflict points.

How They Function and What They Regulate

Traffic signals provide legally enforceable instructions—stop, prepare to stop/clear the intersection, and proceed—using color indications and arrows. They manage conflicts between streams of traffic and pedestrians, often coordinated across corridors to improve flow and safety.

The following list summarizes standard indications and their typical meanings.

• Red: Stop and remain stopped until a permissive indication appears; turning on red is jurisdiction-dependent and subject to signs and local law.
• Yellow (Amber): Warning that the signal will change to red; drivers must stop if they can do so safely before the stop line.
• Green: Proceed if the way is clear; does not remove the duty to yield to pedestrians and conflicting traffic when applicable.
• Arrows: Directional control (e.g., protected left-turn green arrow grants exclusive right-of-way for that movement).
• Flashing Modes: Often used for special operations—flashing red (stop, then proceed when clear) or flashing yellow (proceed with caution)—and for pedestrian beacons.
• Pedestrian Signals: “Walk,” flashing “Don’t Walk,” and countdown timers communicate right-of-way and remaining crossing time.

These standardized indications build a shared language for road users, enabling predictable behavior and enforceable rules at intersections and crossings.

Types of Traffic Signals

Signals vary in how they are timed and how they respond to traffic demand. Modern deployments increasingly rely on detection and data-driven control strategies to improve safety and throughput.

Below are common types encountered in practice.

• Fixed-Time: Pre-set cycle lengths and phase splits, often used in downtown grids with consistent demand patterns.
• Semi-Actuated and Fully Actuated: Use detectors (loops, radar, video) to allocate green time based on real-time demand.
• Adaptive: Coordinate timing across corridors with live data, optimizing for flow and minimizing delay (e.g., SCOOT, SCATS, or proprietary adaptive systems).
• Protected/Permissive Turn Phasing: Combines exclusive turn phases with permissive gaps to balance safety and efficiency.
• Transit/Freight/Emergency Priority: Modifies signals (e.g., green extension, early green, preemption) to favor buses, trams, emergency vehicles, or rail crossings.
• Pedestrian and Bicycle-Specific Signals: Include leading pedestrian intervals, pedestrian hybrid beacons (PHBs), and bicycle signal heads for protected bike movements.

While the technologies differ, each type remains a traffic control device whose core purpose is allocating right-of-way to reduce conflicts and delay.

Why the Classification Matters

Being classified as a traffic control device brings specific design, operational, and legal requirements that affect how signals are deployed and how drivers and pedestrians must respond.

The following points highlight key implications.

• Legal Enforceability: Disobeying signal indications is an offense; interpretations (e.g., right turn on red) depend on jurisdictional rules and posted signs.
• Standards and Warrants: Installation must meet criteria (e.g., warrants in the MUTCD) and follow specified design practices for visibility, placement, timing, and accessibility.
• Safety and Liability: Compliance with standards supports safety outcomes and influences liability in crash investigations and civil claims.
• Accessibility: Requirements such as accessible pedestrian signals (APS), tactile features, and audible indications ensure equitable use.
• Funding and Maintenance: Classification ties signals to public infrastructure programs, asset management, and performance monitoring.

These factors ensure that signals are not ad hoc devices but standardized, maintained infrastructure with clear rules for use and enforcement.

Common Terms and What’s Included

Everyday language varies—stoplights, traffic lights, traffic signals—but the underlying classification is consistent. It’s also useful to distinguish signals from other roadside devices.

The list below clarifies terminology and scope.

• Synonyms: Traffic light, stoplight, signal light, traffic signal—all refer to the same class of traffic control device.
• Included Under the Umbrella: Vehicular and pedestrian signal heads, signal controllers and cabinets, detectors, and associated hardware.
• Not the Same Thing: Street lighting (illumination), warning beacons and signs (also traffic control devices, but not signals), and lane control signals (a related but distinct application typically over freeways).

Understanding the distinctions helps road users and agencies communicate precisely about installations, operations, and compliance.

Summary

Traffic lights are traffic control devices—specifically, regulatory traffic signals that assign right-of-way and control movements at intersections and crossings. Defined in standards such as the MUTCD (US), TSRGD (UK), and the Vienna Convention, they use standardized indications (red, yellow, green; arrows; pedestrian signals) and operate under strict design and legal frameworks to improve safety and efficiency on public roads.

What is considered a traffic signal?

A traffic control signal (traffic signal) shall be defined as any highway traffic signal by which traffic is alternately directed to stop and permitted to proceed.

What counts as running a red light in Virginia?

Virginia law requires all vehicles to stop on a red light signal. Right turns on red are permitted unless otherwise posted. The camera will capture right turn violations on vehicles that proceed without coming to a full stop.

What is a traffic light called?

Traffic signals , also known as traffic lights, traffic lamps, signal lights and stop lights are signalling devices positioned at road intersections, pedestrian crossings, bicycle crossings, and other locations to control competing flows of traffic.

What is the description of traffic?

the movement of vehicles, ships, persons, etc., in an area, along a street, through an air lane, over a water route, etc.. the heavy traffic on Main Street. the vehicles, persons, etc., moving in an area, along a street, etc. the transportation of goods for the purpose of trade, by sea, land, or air.