You see them every day, drivers trying to beat the red light and continue against a steady yellow light.
What a Yellow Light Means
A steady circular yellow or yellow arrow signal is a warning that the related green light is being terminated or that a red light will be shown immediately thereafter.
Think of the yellow light as the beginning of the red light phase, not the end of the green light period. During this phase all vehicles are expected to clear the intersection.
Is it illegal or not?
There are three different yellow light laws in the United States. The most common is the permissive yellow law, the other two are restricted yellow laws.
Under the permissive law, you may proceed through during the entire duration of the yellow change interval.
It may, however, still be unlawful to block the intersection, if you cannot clear it. It may also be unlawful to speed up to beat the red light.
The first of the restricted laws says you may not proceed against a yellow light unless you can completely clear the intersection before the red signal (LA, RI, TN, and WV)
The other restricted law says you may not enter the intersection against a yellow light unless it is unsafe or impossible to stop.
In general, it is recommended that you stop at a yellow light unless you are too close to the intersection to stop safely. If you cannot stop safely, you should carefully continue at your current speed. Clear the intersection as soon as you can, but be aware of crossing bicyclists and pedestrians.
When determining if a stop can be made safely or not, you should also look for vehicles behind you. Do not slam on your brakes in front of the stop line. A tailgater trying to beat the light may not be able to stop in time.
If you are clearly able to stop, but speed up to make the light, you may receive a ticket. You may also get a ticket if you continue through and cannot clear the intersection in time.
Remember, stop at a yellow light, if you can do so safely.