Yellow traffic light

How to read it

The MUTCD says a steady circular yellow warns traffic that the green movement is ending, or that a steady red light will follow immediately, at which point traffic is not to enter the intersection. The rules that applied under the green keep applying while the yellow shows. Pedestrians facing a yellow light, with no pedestrian signal to follow, do not start to cross. In the United States yellow comes only between green and red: the MUTCD does not allow it in the change from red to green. A steady yellow arrow does the same job for a green arrow, warning that the arrow’s movement is ending. This page describes the national standard and isn’t legal advice; the rules at a signal are set by state law and vary from state to state.

Also searched as: amber light, steady yellow light, yellow light.

Can you go through a yellow light?

The MUTCD defines a yellow light as a warning, not as a stop signal, and leaves what a driver must do to state law, which the state manuals word differently. Pennsylvania’s manual says to slow down and prepare to stop, and to continue carefully if already in the intersection or unable to stop safely before it. California’s handbook says to stop if it can be done safely, and otherwise to cross the intersection cautiously. Oregon’s says to stop before entering the intersection, or to drive carefully through it if stopping isn’t safe. Michigan’s goes furthest: it says drivers are required to stop on a yellow light, and if they cannot stop safely, not to speed up but to drive cautiously through.

How long a yellow light lasts

The MUTCD leaves the length to engineering practice. Its guidance is 3 to 6 seconds, with the longer times kept for faster approaches, and a signal’s yellow may not vary from cycle to cycle within the same timing plan. A red clearance interval may follow it, to give more time before conflicting traffic, pedestrians included, is released. The Manual forbids any warning before the yellow, such as a flashing green or a countdown for drivers, noting that research found such displays increase crashes.

Amber, and red with amber, in Britain

British signals call the same light amber, and use it in both directions. In the Department for Transport’s Know Your Traffic Signs, red and amber shown together also mean stop, and traffic does not pass the stop line until green shows. Amber alone means stop, unless it appears after a driver has crossed the stop line or is so close to it that pulling up might cause an accident. The MUTCD has no red-and-yellow phase.

Look-alikes

A flashing yellow light is a different signal: the MUTCD lets traffic proceed through it with caution. A flashing yellow arrow allows a turn after yielding.