So You Think You Know California Traffic Laws:

Somewhere between "green means go" and "red means stop," a lot of drivers picked up a third rule that isn't actually in the vehicle code: that yellow means stop too, just with less urgency. It's an understandable instinct — better safe than sorry — but it's not what California law asks for, and driving as though it were can cause exactly the kind of hard, unnecessary braking that yellow lights exist to prevent.

The California Driver Handbook describes a yellow signal as a caution light: the signal is about to turn red, and the driver's job is to assess the intersection in the moment, not to default to either extreme. If you can stop safely, meaning without a hard brake, without risking a rear end collision from the driver behind you, the law expects you to stop. If you're already far enough into your approach that stopping safely isn't realistic, the same law expects you to continue through the intersection with caution rather than slam the brakes and create a hazard behind you.

The actual violation lives at CVC §21453: running a red light. Entering an intersection while the signal is yellow, and clearing it before the signal turns red, isn't a citation worthy event — it's the law working as designed. What gets a driver a ticket is being in the intersection, or entering it, after the light has already turned red, which is a judgment California leaves to signal timing engineers, not to drivers second guessing themselves mid-intersection.

The practical skill traffic school tries to build here isn't "stop for yellow" or "go for yellow"  it's reading your own stopping distance early enough that the decision is easy by the time the light actually changes. Drivers who get caught in the bad spot, unsure whether to brake or go, are usually the ones who weren't watching the signal until it had already changed. Watch it early, and yellow stops being a dilemma.

CVC §21453