TL;DR: Starting January 1, 2026, California's AB 390 expands the Slow Down, Move Over law so it covers any stationary vehicle on the roadside that is displaying hazard lights or warning devices — not just police cars, tow trucks, and Caltrans vehicles. When you approach one, change to a lane that is not next to it, or slow to a safe speed if you cannot move over. Ignoring the rule is an infraction with a base fine of up to $50, plus court fees. Before your next renewal, run a free California DMV practice test to lock in the updated rule.

What is California's AB 390 Slow Down, Move Over law?

AB 390 is a California law, signed by the Governor in July 2025 and effective January 1, 2026, that rewrites Vehicle Code section 21809 — the rule most drivers know as the Slow Down, Move Over law. The old version protected a short list of vehicles. The new version protects almost any vehicle stopped on the side of the road.

Under CVC §21809, when you drive on a highway and approach a covered stationary vehicle, you have two options: move into a lane that is not immediately next to it, or — if you cannot change lanes safely — slow to a reasonable and prudent speed. AB 390 keeps that two-option structure. It simply makes the list of covered vehicles much longer.

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One detail trips people up: in the California Vehicle Code, "highway" does not only mean a freeway. It means any public road open to vehicle travel. So the AB 390 California Slow Down, Move Over rule applies on city streets and rural two-lane roads, not just interstates.

Who and what does the move over law cover now?

The move over law applies to every driver on a California public road. What changed for 2026 is the list of vehicles you must slow down or move over for. As of January 1, 2026, that list includes:

• Authorized emergency vehicles — police, fire, and ambulance — displaying emergency lights
• Tow trucks displaying flashing amber warning lights
• Marked highway maintenance vehicles displaying flashing amber lights, including Caltrans crews and now every marked maintenance vehicle
• Any other stationary vehicle displaying flashing hazard lights or a warning device, such as cones, flares, or retroreflective triangles

A warning device is anything a driver sets out to flag a roadside hazard. The law specifically names cones, flares, and retroreflective devices — the reflective triangles many people keep in the trunk — but the list is open-ended. The flashing hazard lights built into every car count on their own.

That last bullet is the heart of AB 390. A neighbor changing a flat tire with the hazards on, a rideshare driver stopped with flares out, a delivery van parked behind a reflective triangle — all of them now get the same protection the law once reserved for emergency crews.

What changed from the old California move over law?

Before 2026, section 21809 covered only three categories: authorized emergency vehicles, tow trucks, and stationary marked Caltrans vehicles, each with warning lights flashing. If a regular driver was stranded on the shoulder with hazard lights on, passing traffic had no legal duty to slow down or move over for them.

AB 390 closes that gap. The California move over law for 2026 now reaches "any other stationary vehicle displaying flashing hazard lights or another warning device, including, but not limited to, cones, flares, or retroreflective devices." It also widens the maintenance category from Caltrans-only to every marked highway maintenance vehicle.

The two-step duty — move over if you can, slow down if you cannot — has not changed. What changed is how often you will use it. Think of section 21809 now as a broad stationary vehicle hazard lights law: after January 1, 2026, that stalled sedan with its hazards blinking is no longer just a courtesy stop, it is a legal one.

Why did California expand the move over law?

Every U.S. state has some version of a move over law, and California's has been on the books since 2007. The problem lawmakers kept seeing: the protection stopped at emergency and work vehicles, even though the people most exposed on the shoulder are often everyday drivers dealing with a flat tire or a dead battery.

Roadside breakdowns put people just feet from traffic moving at 55 or 65 mph, with almost no margin for error. Tow operators, the California Highway Patrol, and safety groups have urged drivers for years to treat any stopped vehicle as a hazard. AB 390 turns that advice into a legal duty, so a stranded family on the shoulder gets the same buffer of space as a Caltrans crew.

How to follow the AB 390 move over rule step by step

The rule is easy to follow once it becomes a habit. Here is the sequence:

1. Step 1: Scan far ahead. Look down the road and along the shoulder so you spot a stopped vehicle with plenty of time to react calmly.
2. Step 2: Check for the signal. Flashing hazard lights, amber warning lights, emergency lights, or roadside devices like cones and flares all mean the move over rule applies.
3. Step 3: Move over one lane. On a multi-lane road, signal early and change into a lane that is not immediately next to the stopped vehicle, with due regard for the traffic around you.
4. Step 4: If you cannot move over, slow down. When a lane change would be unsafe or impossible, reduce your speed to a level that is reasonable and prudent for the road, weather, and traffic.
5. Step 5: Pass with space, then merge back. Once you are safely past the stopped vehicle, signal again and return to your normal lane when there is room.

Common mistakes to avoid

The rule is simple, but a few habits get drivers into trouble. Watch out for these:

Swerving at the last second. A sudden lane change next to a stopped car endangers everyone. The law expects an early, signaled, deliberate move — not a panic swerve.

Braking hard when a lane change was safer. Slowing down is the backup option, not the default. If a lane is open and clear, move over instead of stomping the brakes and risking a rear-end crash.

Assuming the rule is freeway-only. AB 390 applies on any public road. A stalled car with hazards on a city street triggers the same duty as one on Interstate 5.

Thinking it only covers emergency vehicles. That was the old law. Since January 1, 2026, an ordinary car, truck, or van with hazard lights or a warning device counts too.

Overcorrecting past a barrier. If the stopped vehicle is behind a guardrail or concrete median, the rule does not apply — do not make an unsafe move you do not need to make.

When does the move over law not apply?

AB 390 includes a common-sense exemption. You do not have to slow down or change lanes if the stopped vehicle is not adjacent to the highway, or if it is separated from the highway by a protective physical barrier such as a concrete median or guardrail. If a car is broken down on the far side of a divided freeway behind a barrier, traffic moving in your direction is not affected by it. The point of the law is to protect people who are genuinely exposed to your lane of travel, not to force risky maneuvers where there is no real hazard.

What does an AB 390 violation cost?

A violation of section 21809 is an infraction with a base fine of not more than $50. California adds state and county penalty assessments and court fees to nearly every traffic fine, so the total printed on your notice is usually several times the base amount. Check your courtesy notice for the exact figure, and pay or contest it on time — an ignored traffic citation can turn into a failure-to-appear hold that complicates your next license renewal.

What this means for California drivers

For most people, AB 390 is a small habit change with a real safety payoff. The move you already make for a police car is now the move you make for everyone stopped on the roadside. Get used to scanning the shoulder, and treat any flashing light as your cue to give space.

If you are studying for your permit or renewing your license, expect the expanded rule to appear on the written test. Our roundup of every California traffic law change for 2026 covers AB 390 alongside the other updates, and our guide to 2025's traffic law changes fills in the recent history. New drivers should also review core defensive driving tips that make moving over second nature. The DMV publishes its own plain-language summary on the 2026 new laws page.

Practice for your California DMV test

The fastest way to make the new move over rule stick is to quiz yourself on it. Our free California DMV practice tests mirror the real exam format with 1,164+ questions across 11 languages, all based on the official California Driver Handbook. Take a full 46-question simulation test and find out whether you are ready for the road.