How must you respond to a flashing red traffic signal?
Correct answer: A – Stop and follow the rules that apply at a stop sign
Under Utah law, a driver facing a flashing red signal must stop at the marked stop line or the required stopping point before entering. After stopping, the driver follows the same right-of-way rules that apply at a stop sign. Proceed only when the roadway is clear and it is lawful to do so.
Source: Utah Driver Handbook — § 9, “Traffic Signals”, Utah Code § 41-6a-307 – Flashing red or yellow signals -- Rights and duties of operators -- Railroad grade crossings excluded

