Does Arizona's three-second minimum yellow-light duration apply to left-turn signals, or only to straight-ahead lights?

Plain-English summary

In 2010 the Arizona Legislature amended A.R.S. § 28-643 to require that the Department of Transportation's traffic-control manual specify a yellow-light duration of at least three seconds. Senator Frank Antenori reported that some municipalities read the rule as excluding left turns and had allowed contractor-installed left-turn signals to use default timers shorter than three seconds. He asked the Attorney General whether the rule covers left turns.

Attorney General Thomas Horne concluded the statute applies to all yellow lights, left turns included. The plain language refers to "yellow light duration" without distinguishing between straight-ahead and turn signals; if the Legislature had wanted to exempt left turns, it would have said so. The legislative history backed this up: the bill sponsor told the House Committee on Transportation and Infrastructure that the measure was intended to apply to both left-hand turns and straight-ahead driving. Under the standard rule of statutory interpretation that plain language controls when a statute is unambiguous (Mid Kansas Sav. & Loan Ass'n v. Dynamic Dev. Corp., 167 Ariz. 122 (1991)), the AG concluded the three-second rule covers every yellow light.

Currency note

This opinion interprets the 2010 version of A.R.S. § 28-643. Check the current statute and traffic-control manual before relying on its three-second specification today.

Background and statutory framework

The opinion quotes A.R.S. § 28-643: "All traffic control devices erected shall conform to the manual and specifications prescribed in § 28-641. The manual shall include the specification that the yellow light duration must be at least three seconds." The AG found no exception in that language for left-turn signals. He also cited the bill sponsor's statement that the requirement was meant to cover left-hand turns and straight-ahead driving.

For a local authority reviewing its signals, the opinion's answer is to include left-turn yellow phases when applying the three-second specification. The opinion does not decide what happens to a traffic citation involving a shorter yellow phase.

Common questions

Q: What was the practical effect of this opinion?
A: The AG concluded that the three-second specification covers left-turn yellows as well as straight-ahead yellows. The opinion does not address the validity of traffic citations.

Q: Is three seconds the only requirement?
A: The statute quoted in the opinion says yellow-light duration "must be at least three seconds." The opinion does not set a maximum duration or discuss how to select a longer one.

Q: Does the opinion say whether a short yellow phase invalidates a ticket?
A: No. The request and the answer address only whether the three-second specification applies to left-turn signals. The AG did not analyze ticket validity or enforcement defenses.

Q: Does this apply only to local roads or also to state highways?
A: A.R.S. § 28-641 covers the state-wide manual all jurisdictions must follow, so the requirement applies to traffic control devices statewide, not just local roads.

Citations and references

Statutes:

• A.R.S. § 28-643 (yellow light duration)
• A.R.S. § 28-641 (uniform manual for traffic control devices)
• 2010 Ariz. Sess. Laws ch. 213, § 1

Cases:

• Mid Kansas Sav. & Loan Ass'n v. Dynamic Dev. Corp., 167 Ariz. 122, 804 P.2d 1310 (1991), plain-language rule
• State v. Gomez, 212 Ariz. 55, 127 P.3d 873 (2006), tools of statutory construction

Source

• Landing page: https://www.azag.gov/opinions/i11-005-r11-008
• Original PDF: https://www.azag.gov/sites/default/files/2025-06/I11-005.pdf

Original opinion text

To:

The Honorable Frank Antenori

Arizona State Senate

Question Presented

Does Arizona Revised Statutes ("A.R.S.") § 28-643, which requires a minimum yellow light duration of three seconds, apply to yellow lights for left turns?

Summary Answer

Under A.R.S. § 28-643, all traffic control devices must conform to the specification that the yellow light duration be at least three seconds. A plain reading of the statute indicates that the statute's language applies to all traffic lights, including those for left turns, and the legislative history confirms this interpretation.

Background

Arizona Revised Statutes § 28-641 provides that the Director of the Department of Transportation "shall adopt a manual and specifications for a uniform system of traffic control devices for use on highways in this state." In the 2010 Regular Session, the Arizona Legislature enacted and the Governor signed House Bill 2338, amending A.R.S. § 28-643. See 2010 Ariz. Sess. Laws ch. 213, § 1. The measure provides as follows:

> Local authorities in their respective jurisdictions shall place and maintain the traffic control devices on highways under their jurisdiction as they deem necessary to indicate and to carry out this chapter or local traffic ordinances or to regulate, warn or guide traffic. All traffic control devices erected shall conform to the manual and specifications prescribed in § 28-641. The manual shall include the specification that the yellow light duration must be at least three seconds.

According to your letter, some municipalities have determined that the statute's last sentence does not apply to yellow light durations for left turns and have allowed the default timers on yellow lights installed by private contractors to run for periods of time less than three seconds on left turns.

Analysis

I. The Plain Meaning of "Yellow Light Duration" in A.R.S. § 28-643 Includes the Duration of Both Yellow Lights for Straight-ahead Driving and Yellow Lights for Left Turns.

If a statute's language is plain and unambiguous, courts interpret the language as written without resorting to other methods of statutory interpretation. Mid Kansas Sav. & Loan Ass'n v. Dynamic Dev. Corp., 167 Ariz. 122, 128, 804 P.2d 1310, 1316 (1991). In this case, the statute does not distinguish between traffic lights for straight-ahead driving and those for left turns. If the Legislature intended the term "yellow light duration" to apply only to straight-ahead driving, it could have specifically exempted left turns. It did not do so and instead chose more general language applicable to both left turns and straight-ahead driving. The statute's plain language encompasses the duration of yellow lights for left turns because these devices fall within the general term "yellow light duration."

II. The Legislative History of A.R.S. § 28-643 Confirms that the Phrase "Yellow Light Duration" Applies to Left Turns.

The available legislative history for § 28-643 confirms that the legislature did not intend to distinguish between left turns and other yellow lights. See State v. Gomez, 212 Ariz. 55, 57, ¶ 11, 127 P.3d 873, 875 (2006) (noting that where a statute is ambiguous, the court may consider other tools of statutory construction). For example, legislative records demonstrate that in response to questions regarding the measure, the bill's sponsor indicated that it was intended to apply to both left-hand turns and straight-ahead driving. See Minutes of H. Comm. on Transp. & Infrastructure, 2010 Leg., 2d Reg. Sess. at 3 (Jan. 28, 2010).

Conclusion

Under A.R.S. § 28-643, the requirement that the duration of a yellow light be at least three seconds applies to both left turns and straight-ahead driving. Consistent with the legislative history, a reading of the plain language "yellow light duration" compels the conclusion that the rule applies to all yellow lights.

Thomas C. Horne

Attorney General