The yellow diamond with a traffic signal symbol warns that a signalized intersection is ahead before you can see it, or before you can see it in time. It is posted where a curve, hill, trees, or high approach speeds hide the signal until stopping would be difficult.
Its practical message is about the light you cannot see yet: it may already be red, or turn red before you arrive. Drivers who know the sign start covering the brake and checking mirrors early; drivers who ignore it meet a stale green at full speed.
Slow down, extend your following distance, and be ready to stop. Glance at your mirrors so you know whether traffic behind you is prepared too. If the signal comes into view already green, treat it as stale: it has been green for an unknown time and may change before you arrive.
Tests pair it with Stop Ahead and Yield Ahead, the same idea for hidden stop and yield signs; the symbol inside the diamond tells you which control is coming. It is a warning sign, so it commands nothing by itself; the signal it announces does that.
This sign appears in 11 questions across 11 of our state banks, on Driver License practice tests. Start with your state:
What roadway control does the displayed warning sign tell you to expect ahead?
Why: The traffic-signal-ahead warning tells a driver that a traffic signal controls the roadway ahead. Therefore, the proposed response is "A traffic signal".
Every practice test explains its answers this way. Pick your state and take one free; no sign-up.
Choose your stateA traffic signal is ahead where you cannot yet see it, or cannot see it in time to stop at speed. Slow down and be ready for the light to be red when it comes into view.
Because at the posted speed, seeing the signal only when you crest the hill or exit the curve leaves too little distance to stop. The sign buys you the braking distance the geometry took away.
A light that has been green for an unknown time and may change at any moment. When a signal-ahead sign hides the light until late, treat any green you finally see as stale: cover the brake and be ready.
Yellow diamond shape, black symbol, and no command of their own. They tell you what is coming, a signal, a curve, a merge, so you can adjust speed and position before you get there.
As symbol identification, and in scenario form: what should you do when you see it, with the tested answer being slow down and prepare to stop, not maintain speed because the light might be green.