Traffic signals

Key points

1. Vertical signals have red on top, yellow in the middle and green at the bottom.

   Source: Handbook p. 55

   “Vertical traffic lights have a red light at the top, a yellow light in the middle, and a green light at the bottom.”
   Idaho Driver's Handbook, Handbook p. 55

2. On a steady yellow, stop if you have not entered and can stop safely; if already in, continue and clear it.

   Source: Handbook p. 55

   “If you have not entered the intersection and can come to a safe stop, you should do so. If you are already in the intersection, you should continue moving and clear it safely.”
   Idaho Driver's Handbook, Handbook p. 55

3. A flashing yellow light means slow down, look carefully for hazards and proceed with caution.

   Source: Handbook p. 55

   “You should slow down, look carefully for hazards, and proceed with caution.”
   Idaho Driver's Handbook, Handbook p. 55

4. A flashing red light means stop completely, yield, then go when clear.

   Source: Handbook p. 55

   “A flashing red indication means stop. You must come to a complete stop, yield to cross traffic or pedestrians, and then proceed when clear.”
   Idaho Driver's Handbook, Handbook p. 55

5. On a steady red arrow, no turn is allowed in that direction until a green or yellow indication allows it.

   Source: Handbook p. 55

   “While the steady red arrow indication is displayed, no turn is permitted in the direction of the arrow until a green or yellow light indication allows movement.”
   Idaho Driver's Handbook, Handbook p. 55

6. A flashing yellow arrow allows turns after yielding to oncoming traffic and pedestrians.

   Source: Handbook p. 56

   “The flashing yellow arrow means turns are allowed after yielding to oncoming traffic and pedestrians in crosswalks.”
   Idaho Driver's Handbook, Handbook p. 56

7. On a green light in the left turn lane, yield to oncoming traffic and pedestrians before turning.

   Source: Handbook p. 56

   “If you are in the left-turn lane, you must yield to oncoming traffic and pedestrians in crosswalks before turning left.”
   Idaho Driver's Handbook, Handbook p. 56

8. Do not enter on green unless there is room to get all the way through the intersection.

   Source: Handbook p. 56

   “You should not enter the intersection unless there is sufficient space on the other side of the intersection for your vehicle to completely pass through the intersection”
   Idaho Driver's Handbook, Handbook p. 56

9. When a signal is not working, treat the intersection as a four way stop.

   Source: Handbook p. 56

   “Whenever a traffic signal is not functioning, treat the intersection as a four-way stop.”
   Idaho Driver's Handbook, Handbook p. 56

3 questions from the Idaho practice test

1. 1. When facing a steady yellow circular light and able to stop safely, what should a driver do?

   1. Stop before entering the intersection
   2. Speed up and enter before the red light appears
   3. Continue at the same speed because yellow means go
   4. Back up if already inside the intersection
   Show answer

   Stop before entering the intersection. A steady yellow circular indication warns that the signal is about to change to red. If the driver has not entered the intersection and can make a safe stop, stopping is the appropriate response. Accelerating turns a warning into a race with the signal, and continuing automatically ignores the caution. A vehicle already in the intersection should clear it safely, so backing up is also unsafe. Look ahead early enough to stop smoothly rather than braking at the line.

2. 2. How should a driver respond to a flashing yellow circular traffic signal?

   1. Stop and remain stopped until a green light appears
   2. Treat it as a flashing red signal and yield after stopping
   3. Accelerate because cross traffic must stop
   4. Slow down, check carefully for hazards, and proceed with caution
   Show answer

   Slow down, check carefully for hazards, and proceed with caution. A flashing yellow circular indication is a caution signal, so the driver should reduce speed, scan for conflicts, and continue only when the path is safe. It does not impose the complete stop required by a flashing red indication. The tempting red-signal choice changes the meaning of the light and could cause an unnecessary stop, while accelerating removes the time needed to spot a hazard. Use the signal as a prompt to look carefully, especially for vehicles, pedestrians, or road conditions that are not immediately obvious.

3. 3. When turning left on a green circular signal, which traffic must you yield to before turning?

   1. No one, because a green signal protects every left turn
   2. Only vehicles approaching from the right
   3. Oncoming traffic and pedestrians in crosswalks
   4. Only pedestrians who are outside the crosswalk
   Show answer

   Oncoming traffic and pedestrians in crosswalks. A green circular signal permits movement, but it does not protect a left turn from conflicts. Idaho requires the driver in the left-turn lane to yield to oncoming traffic and pedestrians in crosswalks before turning. The driver must judge when the opposing lane and the crossing are clear. A green light is therefore not permission to turn across an approaching vehicle, and the rule is not limited to traffic from one side. Keep the wheels straight while waiting, scan the crosswalk, and turn only through a safe opening.

Source: the Idaho Driver's Handbook, Highway & Vehicle Knowledge. This lesson is a plain English summary, not the law itself; where it differs, the manual and the statute govern. Last checked 2026-09-27.