ARS 28-729 is Arizona’s lane-use statute. It requires you to keep your vehicle entirely within a single marked lane whenever the road has two or more clearly marked lanes, and it prohibits moving out of that lane until you have first confirmed the change can be made safely.1Arizona Legislature. Arizona Code 28-729 – Driving on Roadways Laned for Traffic The shorthand “28-729.1” that shows up on many tickets refers to paragraph 1 of that statute, which is the provision most drivers encounter.
What the Statute Actually Requires
Paragraph 1 packs two separate obligations into one sentence. First, you must drive “as nearly as practicable” entirely within a single lane. Second, you cannot cross into an adjacent lane until you have confirmed the movement can be made safely. A single citation can be issued for either failure.
The “as nearly as practicable” language gives limited leeway. Road debris, potholes, strong crosswinds, and construction zones may force a momentary drift. But the law expects you to hold a consistent position within the lane markings whenever conditions allow it. Weaving inside your own lane, even without touching a line, can draw an officer’s attention because the pattern resembles impaired driving.
On the lane-change side, if your move forces another driver to brake or swerve, that is strong evidence the change was not made safely. The burden sits on you to confirm the path is clear before moving.
Signaling the Lane Change
ARS 28-729 tells you when a lane change must be safe. A companion statute, ARS 28-754, tells you how to signal it. Any time you move right or left on a roadway and other traffic could be affected, you must signal continuously for at least the last 100 feet before the maneuver.2Arizona Legislature. Arizona Code 28-754 – Turning Movements and Required Signals At highway speeds, 100 feet passes in roughly one second, so treating it as a minimum rather than a target is the safer approach.
A lane change without signaling can produce a citation under 28-754 on top of a 28-729 violation, meaning two infractions from one merge. Officers frequently note the missing signal when documenting a lane violation because it supports the finding that the driver did not take adequate precautions before moving.
Exceptions: Roundabouts and Motorcycle Lane Filtering
Paragraph 1 opens with a carve-out for two other statutes: ARS 28-778 and ARS 28-903.
ARS 28-778 covers roundabouts. Because roundabouts require vehicles to curve through a circular roadway, strict lane discipline as practiced on a straight road does not always apply the same way, and larger vehicles in particular may need more than one lane to navigate the geometry safely.3Arizona Legislature. Arizona Revised Statutes 28-778 – Roundabouts; Large Trucks; Definitions
ARS 28-903 covers motorcycle lane filtering, which Arizona legalized in September 2022. A rider may pass between lanes only when all four of these conditions are met:
- Surrounding traffic is at a complete stop, not merely slow-moving
- The posted speed limit is 45 mph or less
- The motorcycle’s own speed does not exceed 15 mph
- The road has at least two lanes traveling in the same direction
Lane filtering is not the same as lane splitting, which means riding between moving traffic. Splitting remains illegal in Arizona.4Arizona Legislature. Arizona Revised Statutes 28-903 – Operation of Motorcycle on Laned Roadway; Exceptions A motorcyclist who meets all four filtering conditions does not violate 28-729.
Rules for Three-Lane Roads
Paragraph 2 of the statute handles a narrower situation: roads divided into exactly three lanes. On these roads you may use the center lane only when passing another vehicle (with the road ahead clearly visible and the center lane clear for a safe distance), when preparing for a left turn, or when signs designate the center lane for traffic moving in your direction.1Arizona Legislature. Arizona Code 28-729 – Driving on Roadways Laned for Traffic Using the center lane as a general travel lane outside those conditions is a separate violation of the same statute.
Fines and Points on Your Record
A violation of ARS 28-729 is a civil traffic infraction. There is no jail time and no criminal record. The base fine varies by court, and the amount you actually pay runs substantially higher once Arizona courts add a 68% consolidated surcharge along with fixed assessments and other fees. Total out-of-pocket cost for a lane violation typically lands between $150 and $250, though some jurisdictions run higher.
The conviction also adds two points to your Arizona driving record. ADOT classifies lane violations under “all other moving violations,” the catch-all category that carries two points per offense.5Arizona Department of Transportation. Points Assessment Accumulating eight or more points in a 12-month period triggers a required Traffic Survival School attendance or a license suspension of up to 12 months.6Arizona Department of Transportation. Traffic Survival School Two points alone will not get you there, but combined with a speeding conviction (three points) and one more moving violation, the threshold arrives quickly. For threshold calculations, a violation older than 36 months stops counting, though it remains visible on the record.7Arizona Department of Transportation. A Guide to Understanding the New MVR
Defensive Driving School Dismissal
If you receive a citation under ARS 28-729, you are eligible to attend a state-approved defensive driving course to have the violation dismissed. Arizona courts must allow this option for civil traffic moving violations.8Arizona Legislature. Arizona Revised Statutes 28-3392 – Defensive Driving School; Eligibility Completing the course prevents points from being assessed and eliminates the fine.
The main restriction is timing. You cannot use defensive driving school if you already attended one for a citation issued within the previous 12 months. Eligibility is measured from the date of your last eligible violation, not from the date you completed the earlier course.9Arizona Judicial Branch. Defensive Driving Schools
Commercial driver license holders face an important exception. If you were driving a vehicle that requires a CDL when the violation occurred, the court cannot dismiss the conviction through defensive driving. It must report the violation to ADOT. A CDL holder who was driving a personal Class D or Class M vehicle at the time, and not using it for commercial purposes, can still use the defensive driving option.
Extra Consequences for CDL Holders
Beyond the defensive driving restriction, CDL holders face federal exposure that other drivers do not. The FMCSA classifies “making improper or erratic traffic lane changes” as a serious traffic violation under 49 CFR 383.51.10eCFR. 49 CFR 383.51 – Disqualification of Drivers A single conviction on its own does not trigger disqualification, but repeat convictions escalate quickly:
- A second serious violation within three years brings a 60-day disqualification from operating any commercial motor vehicle
- A third within three years brings a 120-day disqualification
The three-year window covers any combination of serious traffic violations. A lane change violation followed by a speeding conviction in a CMV within that window counts as two strikes. For someone whose income depends on holding a CDL, a two-point lane ticket in Arizona can become a career issue if it is not the first one.
Out-of-State Drivers
Arizona belongs to the Driver License Compact, an interstate agreement under which member states share traffic convictions.11Arizona Legislature. Arizona Code 28-1852 – Adoption of Compact A lane conviction in Arizona will be reported to your home state, which then applies its own point system, surcharges, and other consequences. The reverse also holds: an Arizona-licensed driver convicted of a lane violation in another compact state will have that conviction reported to ADOT, which treats it under Arizona’s point rules. Ignoring an out-of-state citation typically results in a license hold or suspension once the home state processes the report.
Why This Statute Matters More Than the Fine Suggests
Failure to maintain a lane is one of the most common reasons officers initiate traffic stops, and it is frequently the stated basis for stops that lead to DUI investigations. An officer who observes a vehicle weaving within its lane, touching a lane marker, or drifting across a line has legal grounds to pull the driver over. A single instance of crossing the fog line can be enough.
During the stop the officer evaluates whether the lane deviation was caused by distraction, fatigue, or impairment. If the officer observes signs of intoxication, the encounter shifts from a civil traffic matter into a DUI investigation. Courts have generally upheld these stops as constitutionally valid provided the officer can articulate the specific lane deviation observed. Dashcam footage is routinely used to document those observations and often becomes the central evidence if the stop is later challenged.
For drivers who are not impaired, the practical point is that even minor lane deviations from glancing at a phone, adjusting the radio, or reaching for something on the passenger seat can result in a stop and a citation. The statute does not require you to cross fully into another lane. Touching a line, or repeated weaving inside your own lane, is enough for an officer to act.