At controlled intersections, traffic lights are installed to keep multiple lanes of traffic flowing and prevent crashes. These signal lights are programmed to avoid conflicts between road users while allowing traffic to move through the intersection as freely as possible. This article will teach you how to interpret traffic lights.

Traffic lights can be displayed vertically or horizontally, though the vertical configuration is prevalent in most states. In vertical arrangements, the red light will appear at the top of the signal board and the green light will appear at the bottom. When organized horizontally, the red light appears on the left and the green light appears on the right.

Every road user must abide by all directions given by signal lights at an intersection. If traffic lights are present at an intersection but are inoperative for any reason, drivers must think of the signals as representing a four-way stop sign (read more about this further down). Now, let’s discuss the different types of signal light you can expect to see at intersections.

A green traffic light at an intersection indicates that you may drive straight across the intersection without stopping. Though, catching a glimpse of green light on your approach does not mean you can plow straight through without further consideration! Depending on when the light changed to green, other drivers may still be occupying the intersection. Always check the road ahead and to your left and right before proceeding – even on a green light.

Drivers should monitor the traffic light as they approach the intersection, to form an estimate of how much time remains before the green light changes to yellow. A signal light that has only just turned green is known as a “fresh green signal”, while a light that has been green for a while is known as a “stale green signal”. Consider the following points when approaching a green light:

If you are planning to turn left or right on a green light, make sure there are no other traffic lights indicating that the turn is not permitted before you proceed. When turning left on a solid green light, be sure to yield to all opposing traffic moving through the intersection before executing the turn.

Arrow signals are placed at some busier intersections to facilitate the flow of traffic wishing to turn rather than drive straight through. If you see a green arrow light when approaching an intersection, you are free to turn in the same direction that the arrow is pointing. Most often, the arrow will indicate a left turn.

Green arrow signals tell drivers that the turn they are making is “protected”, which means that all opposing traffic will be halted by a red signal light. You should not need to yield to pedestrians or other vehicles, though you must still be vigilant when moving through the intersection. Make sure you are in the correct lane to make the protected turn before proceeding.

Note that a green arrow signal only refers to a turn. Motorists wishing to drive straight across the intersection must wait for the solid green signal light to appear.

Yellow or amber traffic lights mark the transitional period between a green signal and a red signal. Motorists must come to a stop at an intersection if they approach as the yellow light is displayed. Passing through an intersection on a yellow light is dangerous.

The only exception to this rule is when a green light turns to yellow at the last moment before you enter the intersection, therefore stopping abruptly would be more hazardous than carrying on. For instance: if the driver to your rear would have to brake suddenly to avoid hitting you, it is safer to keep moving even though the signal has changed.

Driving through an intersection under a yellow signal can usually be avoided by paying attention on your approach and keeping speed to a minimum.

A flashing yellow signal light instructs drivers to slow down and yield to cross traffic before driving through the intersection. The rules concerning flashing yellow signals are much the same as they are for YIELD signs. When approaching a flashing yellow light, you must be prepared to stop.

As with green arrow signals, yellow arrow signals only refer to traffic wishing to move in the direction indicated by the arrow. Motorists in this lane should treat a yellow arrow signal as they would a standard yellow signal when traveling straight across an intersection. When this signal is displayed, drivers wishing to make the indicated turn must come to a stop, unless continuing through the intersection would be the safer choice. If the yellow signal arrow is flashing, motorists must treat it as a YIELD sign.

A red traffic light means that traffic may not proceed straight through an intersection. When approaching a red light, you must come to a complete stop at the stop line, prior to the first line of the crosswalk or before any part of your vehicle enters the intersection. Wait for a green light before you proceed. Other rules may apply when seeking to turn right under a red light, as discussed below.

Motorists are usually permitted to turn right under a red light, unless a road sign posted at the intersection suggests otherwise. The rules concerning right turns on red vary a little around the country, so be sure to check your state’s driving manual for local information.

When turning right under a red traffic signal, motorists MUST yield to all cross traffic before turning. Caution must be used when making this turn at an intersection.

Turning left under a red traffic signal is not permitted at intersections, except when turning from a one-way street onto another one-way street. Keep a lookout for posted road signs indicating that a left turn is not permitted, even under these circumstances. Yield to pedestrians and other traffic when making a left turn on red from a one-way street onto another.

Flashing red signal lights can be interpreted the same way as STOP signs. Traffic must come to a full stop before entering the intersection and proceed one vehicle at a time, while observing proper right-of-way rules.

A red arrow signal indicates that a turn in that direction is not permitted until the light changes to green. Stop in the appropriate lane for the turn you wish to make and wait for a green signal arrow to appear.

Malfunctioning or inoperative traffic lights can easily lead to chaos if motorists at an intersection do not know how to respond appropriately. If you encounter inoperative signal lights, you must treat the intersection as if it were posted with four-way STOP signs. This means that traffic moving in all four directions must come to a complete stop. Drivers may proceed through the intersection one-by-one, in the order in which they arrived. When two or more motorists arrive at the same time, each must yield to the drivers on their right.

Other types of flashing signal light are used to warn drivers about special conditions in an area or upcoming hazards. For instance:

High-intensity Activated Crosswalk (HAWK) beacons are sometimes installed at mid-block crosswalks, where traffic control measures are warranted but standard signal lights are not appropriate. You may also encounter them outside emergency response facilities. These hybrid beacons allow pedestrians to make a protected crossing, using the crosswalk.

Hybrid beacon signal stages (and how you should respond to them) are detailed here:

A dark signal (no lights).This indicates that no action is required from motorists, as no pedestrians have activated the crosswalk. You may drive straight over the crosswalk without stopping or yielding.

Flashing yellow lights.When a pedestrian activates the crosswalk, the beacons will flash yellow for several seconds. This is a warning to motorists that the signals will change but does not require any further action. You may drive straight over the crosswalk.

Steady yellow light.As with standard traffic lights, a steady yellow light indicates that motorists must stop prior to the crosswalk, unless it is not safe to do so.

Steady red light.After a few seconds of steady yellow light, the signal will switch to steady red. All vehicles must remain stopped before the crosswalk as pedestrians cross.

Flashing red light.This signifies the end of the protected pedestrian crossing period. Vehicles must remain stopped and wait for all pedestrians to clear the crosswalk before proceeding. If you approach a hybrid signal with a flashing red light, you must stop completely to allow all remaining pedestrians time to finish crossing.

A dark signal (no lights).The HAWK signal will become inactive again once the pedestrian crossing cycle has finished.

Keep in mind that drivers are NOT required to stop at a hybrid beacon with no active lights. A dark beacon does not indicate a signal malfunction, as it would at ordinary traffic lights.

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