Traffic Lights

Traffic Lights Rules and Meanings: The Definitive Guide

by Zutobi · Updated May 03, 2023

Traffic signals are used to control traffic at intersections by guiding and regulating the flow of traffic. Drivers, cyclists, and pedestrians must obey and understand the different traffic signals.

Traffic signals can be 3 colors (red, yellow, and green) that are either flashing or steady.

We’ll go through all of the different traffic lights, rules, and meanings in this article.

If you prefer video, we’ve made a great explainer video on the subject:

Steady Traffic Signals

Red Traffic Light

Cars waiting in front of red traffic lights

A red light means that you must come to a complete stop and remain stopped until the light turns green. Never run a red traffic light, it’s very dangerous and also illegal.

In some states, you are allowed to proceed in certain circumstances. In California for example, there are two exceptions to this rule unless otherwise signed. If safe, you are allowed to:

  • Turn right after coming to a complete stop, and yielding to traffic and pedestrians in your path
  • Make a left turn after coming to a complete stop, but ONLY if turning from a one-way street onto another one-way street. Yield to traffic and pedestrians in your path

However, you are never allowed to turn on red if there is a ‘NO TURN ON RED’ sign.

Remember that these exceptions do not apply to all states. Make sure to check the specific rules in your state driver’s handbook.

Yellow Traffic Light

Yellow traffic light

A yellow light indicates that the green light is about to end – you must stop unless unable to safely do so. Treat a yellow light as the beginning of a red light, as opposed to the end of a green light.

Green Traffic Light

Green traffic light

A green light means ‘GO’. Yield to vehicles, cyclists, and pedestrians still in the intersection.

Always approach an intersection at a speed that allows you to slow down and stop if the light changes.

Flashing Traffic Lights

Flashing Traffic Signals are generally used to warn road users of dangerous intersections.

There are only two types of flashing lights:

  • A flashing red light
  • A flashing yellow light

A Flashing Red Light

Red flashing traffic light

Treat a red flashing light as a ‘STOP’ sign and apply the right-of-way rules.

A Flashing Yellow Light

Yellow flashing traffic light

A flashing yellow light tells you to slow down and prepare to stop. It is used to warn drivers of danger ahead (e.g. a school crossing). Yield to any vehicles, cyclists, and pedestrians in the intersection.

Traffic Signals with Arrows

Car waiting in front of a red traffic light arrow and green traffic light
Arrows are used to help control turning traffic.

Red Arrow

Traffic signals red arrow

A red arrow means that you must not turn in the direction of the arrow. Wait for a green signal or arrow to appear before you turn.

Yellow Arrow

Yellow traffic light arrow

A yellow arrow indicates that you must stop, unless unable to safely do so (e.g. if in the intersection).

Flashing Yellow Arrow

Flashing yellow traffic light arrow

A flashing yellow arrow means that you are allowed to turn, but must do so carefully. Oncoming traffic will face a green light and have the right-of-way. Yield to oncoming traffic and pedestrians.

Green Arrow

Green traffic light arrow

A green arrow means ‘GO’. You can make a protected turn in the direction of the arrow – meaning that oncoming vehicles, cyclists, and pedestrians are stopped by red lights. Yield to vehicles, cyclists, and pedestrians still in the intersection.

What Do You Do if a Traffic Light Is Not Working?

Malfunctioning Traffic Lights

Malfunctioning traffic lights

Treat an out-of-order traffic light as a 4-Way Stop sign – proceed according to the ‘right-of-way’ rules unless otherwise indicated by an officer or another authorized person.

Lane Use Control Signals

These signals are overhead lane signals used to indicate which lanes that can be used at a specific time.

Lane use control signals
  • Red X – the lane is closed. You must not drive in this lane.
  • Yellow X – the lane is about to close. Move away from this lane.
  • Green arrow – the lane is free to use without restrictions

You will often see these lights on reversible lanes on the highway. A reversible lane may be open in one direction during morning commute, and in the other direction in the afternoon.

Cars driving on road where lane use control signals are used
Don’t drive in a reversible lane unless there’s a green arrow above

Where Should You Stop at Traffic Lights?

  • Traffic lights with stop line or crosswalk – stop just before the stop line/crosswalk. Don’t stop too far away from the line as some signals have detectors near the line, and won’t change to a green light unless a waiting vehicle is detected
  • Traffic lights without stop line or crosswalk – stop before entering the intersection
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