Arizona’s left lane law, set out in ARS 28-721, requires any driver moving slower than the surrounding flow of traffic to stay in the right-hand lane on a multi-lane road. The left lane is treated as a passing lane. Camping in it while faster traffic stacks up behind you is a civil traffic violation that carries a fine, court surcharges, and two points on your driving record.1Arizona Legislature. Arizona Code 28-721 – Driving on Right Side of Roadway; Driving on Shoulder; Exceptions; Education
What Triggers the Keep-Right Rule
The statute’s trigger is not the posted speed limit. It’s the actual speed of traffic around you. The exact language requires drivers going “less than the normal speed of traffic at the time and place and under the conditions then existing” to drive in the right-hand lane or as close as practicable to the right edge of the roadway.1Arizona Legislature. Arizona Code 28-721 – Driving on Right Side of Roadway; Driving on Shoulder; Exceptions; Education
This catches a lot of Arizona drivers off guard. Doing exactly the speed limit in the left lane while everyone else does five or ten over doesn’t make you legal. If the cars around you are moving faster, the law says get right.
When the Left Lane Is Allowed
ARS 28-721 lists specific situations where you can be in the left lane even if you’re slower than surrounding traffic:
- Overtaking and passing another vehicle traveling in the same direction. Once the pass is complete, you’re expected to move back right.
- Preparing to turn left at an intersection, into a private road, or into a driveway.
- Driving on a road where the right half is closed or obstructed, such as an active construction zone.
- Driving on a road officially designated and signed for one-way traffic, where the keep-right framework doesn’t apply the same way.
Heavy congestion isn’t a listed exception. In practice, when every lane is crawling at the same pace, the “less than the normal speed of traffic” trigger isn’t really activated because no lane is moving faster. That’s different from the statute granting a right to sit in the left lane during a traffic jam.
Where the Rule Applies
The keep-right requirement applies on any roadway with two or more clearly marked lanes for traffic moving in the same direction. Interstates like I-10 and I-17 are the obvious case, but the rule reaches any multi-lane road, including state routes and urban arterials with two or more travel lanes each way.
Signs reading “Slower Traffic Keep Right” reinforce the rule, but the legal duty exists whether or not a sign is posted. ARS 28-721 does not condition the obligation on signage.1Arizona Legislature. Arizona Code 28-721 – Driving on Right Side of Roadway; Driving on Shoulder; Exceptions; Education
Emergency Vehicles Override Everything
If you’re in the left lane and an emergency vehicle approaches with lights and sirens, the ordinary lane rules stop mattering. ARS 28-775 requires every driver to yield, pull to a position parallel to and as close as possible to the right edge or curb, and stop there until the emergency vehicle passes.2Arizona Legislature. Arizona Code 28-775 – Authorized Emergency Vehicles; Approaching Holding your left lane in that situation is a separate, more serious violation than a routine keep-right ticket.
Fine and Points
A left lane violation is a civil traffic infraction. Fine amounts vary by court because Arizona’s justice courts set their own schedules. The Pinal County Justice Court, for example, lists violations of ARS 28-721 through 28-736 at $235.3Pinal County Justice Courts. Fine Chart Surcharges and assessments typically push the total higher, and other courts around the state may charge more or less.
The Motor Vehicle Division assigns 2 points to the driver’s record. A left lane violation falls under the catch-all category covering “any other traffic regulation that governs a vehicle moving under its own power.”4Arizona Judicial Branch. MVD and Courts Training Manual Two points alone won’t cost you your license, but they stack:
- 8 to 12 points in 12 months: the MVD may assign Traffic Survival School. If you’ve attended TSS in the past 24 months, a three-month suspension replaces the school option.
- 13 to 17 points in 12 months: three-month suspension, no TSS option.
- 18 to 23 points in 12 months: six-month suspension.
- 24 or more points in 36 months: one-year suspension.
The accumulation window runs from the date of your most recent violation, not the conviction date.4Arizona Judicial Branch. MVD and Courts Training Manual A single left lane ticket rarely triggers any of these thresholds, but paired with a speeding ticket or two, it adds up faster than most drivers expect.
Proposed Changes to the Penalty
Arizona legislators have tried to attach a dedicated fine to left lane violations. During the 2025 session, House Bill 2235 proposed new signs on controlled-access highways reading “Left lane for passing only, slow traffic keep right” and a specific civil penalty for violations. The introduced version set the penalty at $500.5Arizona Legislature. HB 2235 – House Bill Summary A later engrossed version lowered it to $200.6Arizona Legislature. HB 2235 – House Bill Summary – House Engrossed The bill did not pass, so left lane violations are still handled as ordinary civil traffic infractions without an enhanced fine.
Contesting a Ticket
If you’re cited under ARS 28-721, you can request a hearing rather than pay the fine. The response deadline is printed on the citation. Missing it can result in a default judgment, late fees, and potentially a bench warrant.
The cleanest defense is showing you were inside one of the statute’s exceptions: passing, preparing to turn left, or driving with the right side of the road obstructed. Dashcam footage, GPS data documenting a lane change, or testimony about road conditions can support that. Civil traffic cases carry a lower burden of proof than criminal ones, but a judge still needs a reason to dismiss, and a general sense that you weren’t going that slow usually isn’t enough.