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 (HB 2338) to require that the manual the Department of Transportation publishes for traffic control devices include the specification that yellow lights last at least three seconds. After the amendment took effect, some municipalities concluded that the three-second rule applied only to yellow lights for straight-ahead driving, not to yellow lights for left-turn movements. They allowed contractor default timers (often shorter than three seconds) to control left-turn yellows. Senator Frank Antenori asked the Attorney General whether that reading was correct.

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 v. Dynamic Dev., 167 Ariz. 122 (1991)), the AG concluded the three-second rule covers every yellow light.

Currency note

This opinion was issued in 2011. Subsequent statutory amendments, court decisions, or later AG opinions may have changed the analysis. Treat this page as historical context, not current legal advice. Verify current law before relying on any specific rule, deadline, or remedy mentioned here. The basic three-second rule has remained in place but the broader photo-enforcement statutory framework has changed several times.

Background and statutory framework

Arizona's photo-enforcement (red-light camera) program was high-profile in 2010-2012, and the three-second yellow-light requirement was one of several legislative responses to a public concern that camera enforcement was being deployed at intersections with shorter yellows than safety engineers recommend. Federal Highway Administration and AASHTO guidance had long suggested that yellow phases scale with speed limit and intersection geometry, and a strong body of traffic-engineering literature pointed to inadequate yellow times as the dominant cause of "rolling-red" violations.

The 2010 amendment placed the three-second floor in the manual the Director of ADOT publishes under § 28-641 and required all "traffic control devices" to conform to it. By forcing left-turn yellows to also clear three seconds, the AG's interpretation pushed back against contractor defaults that had been common (some left-turn signals ran 2.0 to 2.5 seconds, optimized for throughput rather than safety).

The opinion is short by AG-opinion standards but functioned as significant traffic-law guidance. Municipalities and contractors that ignored it risked photo-enforcement citations being voided in court and potential litigation from injured parties.

Common questions

Q: What was the practical effect of this opinion?
A: Cities and contractors with left-turn yellows shorter than three seconds had to retime them. Drivers who were ticketed at intersections with non-compliant yellow phases gained a possible defense to enforcement actions.

Q: Is three seconds the only requirement?
A: No. Three seconds is the floor in A.R.S. § 28-643. Engineering practice often calls for longer yellows depending on speed limit and intersection geometry. The statute is a minimum, not a target.

Q: How does this interact with red-light cameras?
A: Photo-enforcement systems trigger after a vehicle enters an intersection on red. If the yellow phase is too short, drivers do not have enough time to stop safely once the yellow appears, which has been the basis of several legal challenges to camera tickets. A non-compliant yellow phase undercuts the enforcement basis for the citation.

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 (HB 2338)

Cases:

• Mid Kansas Sav. & Loan 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