AB 390 creates a statutory duty for any motorist approaching certain stationary vehicles on a highway to either change lanes away from the stopped vehicle when safe and practicable or, if a lane change isn’t possible, reduce speed to a safe, reasonable level before passing. The rule applies broadly to authorized emergency vehicles, tow trucks, marked highway maintenance vehicles, and other stationary vehicles that display hazard lights or use warning devices such as cones, flares, or retroreflective devices.
The provision aims to reduce collisions that endanger first responders, tow operators, maintenance crews, and motorists stopped at the roadside by setting a uniform driver behavior standard. It adds an enforceable obligation on drivers while carving out limited exceptions where the stopped vehicle is not adjacent to the highway or is protected by a physical barrier.
At a Glance
What It Does
The bill requires drivers approaching a stationary covered vehicle to, before passing in the lane immediately next to that vehicle, move into an available lane that is not immediately adjacent to it when it is safe and lawful to do so; if a safe lane change isn’t practicable, the driver must slow to a reasonable and prudent speed for prevailing conditions. The obligation is subject to directions from a peace officer.
Who It Affects
All motorists on California highways; operators of authorized emergency vehicles, tow trucks, and highway maintenance units (including contractor crews); and agencies responsible for roadside work and traffic safety messaging. The rule reaches private or other vehicles using hazard lights or warning devices at the roadside.
Why It Matters
AB 390 standardizes driver conduct around a wide set of stopped vehicles and warning setups, broadening protections beyond officially marked emergency vehicles to include tow and maintenance operations and any roadside hazards that display lights or physical devices. For compliance and risk managers it creates a clear, enforceable driver duty and a new source of liability exposure where drivers fail to move over or slow.
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What This Bill Actually Does
The core operative instruction appears in subdivision (a): when you are driving and you approach a stationary vehicle that is displaying specified warning signals or devices and is adjacent to the highway, you must exercise caution and, before you pass in the lane directly next to that vehicle, do one of two things. First, if there is an available lane that is not immediately adjacent to the stopped vehicle and you can safely and legally move into it, you must change lanes into that lane.
Second, if changing lanes would be unsafe or impracticable, you must reduce your speed to what the statute calls a "reasonable and prudent" level given weather, road, and traffic conditions. The statute also recognizes that a peace officer can direct otherwise.
Subdivision (b) makes noncompliance an infraction, so officers can issue citations rather than seek criminal penalties. The statute caps the maximum fine at fifty dollars, signaling that the legislature intended a low-level traffic enforcement tool rather than a major financial sanction.
That framing affects how likely police are to prioritize enforcement and how courts will treat contested citations.There are two narrow limits to the duty. Subdivision (c) exempts the requirement when the stopped vehicle is not adjacent to the highway or is separated from the highway by a protective physical barrier; in those situations the driver need not change lanes or slow under this provision.
Subdivision (d) defines "highway maintenance vehicle" to include both public-agency-owned vehicles and vehicles owned or operated by private contractors working under government contract, which brings contractor crews explicitly within the statute’s protective reach.Taken together, the statute covers a broader set of roadside scenarios than statutes limited to marked emergency vehicles alone: it reaches tow trucks displaying amber lights, government and contractor maintenance crews, and any vehicle deployed with hazard lights or visible warning devices such as cones, flares, or retroreflective panels. That breadth will affect ordinary motorists (who must make split-second lane decisions), employers and contractors who place crews at the roadside (who gain explicit statutory protection), and law enforcement (which must interpret and enforce the new duty).
The Five Things You Need to Know
Before passing in the lane immediately adjacent to a stationary covered vehicle, a driver must move into an available lane that is not immediately adjacent to that vehicle if it is practicable and lawful to do so.
If a safe lane change is unsafe or impracticable, the driver must slow to a reasonable and prudent speed safe for the existing weather, road, and traffic conditions.
Violating the statute is an infraction punishable by a fine of up to $50.
The duty does not apply when the stopped vehicle is not adjacent to the highway or is separated from the highway by a protective physical barrier.
The statute’s definition of 'highway maintenance vehicle' covers both public agency vehicles and vehicles owned or operated by contractors under contract with those agencies.
Section-by-Section Breakdown
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Driver duty: change lanes or slow before passing a stopped vehicle
This paragraph sets the operative obligation. It requires drivers to approach with 'due caution' and, prior to passing in the lane immediately next to the stopped vehicle, either change lanes away from the vehicle (if an available lane exists and it is safe and lawful) or slow to a reasonable speed. Practically, this places a two-step decision on drivers: first look for and execute a safe lane change; if that’s not possible, moderate speed sufficiently to account for conditions. The provision also includes the common caveat that a peace officer’s directions override the statutory rule.
Enforcement mechanism and penalty
Subdivision (b) classifies violations as infractions rather than misdemeanors or felonies and sets the maximum penalty at $50. That establishes the law as traffic-level enforcement intended to change driver behavior without imposing heavy financial penalties. From an enforcement perspective, the low fine suggests the legislature expected routine traffic enforcement and adjudication rather than major prosecutorial resources.
Exemptions where the stopped vehicle is not adjacent or is protected
This clause removes the obligation when the stopped vehicle is not next to the highway or when a protective physical barrier separates it from the highway. The exemption narrows the duty to situations where the stopped vehicle presents a proximate roadside hazard to passing traffic rather than vehicles entirely off the highway or behind concrete barriers.
Who counts as a highway maintenance vehicle
This definition includes both government-owned/operated maintenance vehicles and vehicles owned or operated by private contractors working under contract with government entities. That explicit inclusion brings contractor crews performing pavement, shoulder, or roadside work within the statute’s protective mandate.
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Explore Transportation in Codify Search →Who Benefits and Who Bears the Cost
Every bill creates winners and losers. Here's who stands to gain and who bears the cost.
Who Benefits
- First responders and emergency personnel — they gain statutory protection when stopping adjacent to highways, raising the baseline expectation that passing traffic will move away or slow.
- Tow operators and roadside service crews — the law expressly covers tow trucks and vehicles using warning devices, which reduces exposure to passing traffic during vehicle recovery or service calls.
- Public and private highway maintenance crews (including contractors) — the definition expressly brings contractor-owned maintenance vehicles under the protection, extending the duty to crews working under contract.
- Occupants of stopped vehicles and nearby pedestrians — drivers who have pulled over to the roadside will face decreased collision risk from passing traffic that must move over or reduce speed.
Who Bears the Cost
- All motorists — drivers must make immediate tactical decisions to change lanes or slow, and doing so may increase stress and introduce lane-change risks in dense traffic.
- Law enforcement agencies — officers must interpret 'practicable,' 'due regard for safety,' and 'reasonable and prudent speed' on a case-by-case basis and will absorb enforcement and citation-processing workload.
- Local agencies and contractors — they may need to re-evaluate worksite placement, training, and signage to ensure crews and traffic interact safely under the statutory standard.
- Courts and traffic adjudication systems — low-dollar infractions can still generate administrative burden, contested hearings, and record-keeping costs for municipal courts.
Key Issues
The Core Tension
The statute pits two legitimate objectives against one another: protecting roadside workers and responders by legally compelling drivers to create distance from stopped vehicles, versus preserving driver discretion and traffic flow where lane changes or speed adjustments may be unsafe, impracticable, or operationally disruptive. The law reduces risk for stationary crews but shifts difficult, context-dependent judgment calls to individual drivers and enforcing officers.
Several implementation questions and trade-offs arise from AB 390’s wording. Key operative phrases—'due caution,' 'if practicable and not prohibited by law,' 'unsafe or impracticable,' and 'reasonable and prudent speed'—are inherently fact-specific and invite case-by-case determinations.
That ambiguity gives officers discretion but also risks inconsistent enforcement across jurisdictions and uncertainty for drivers deciding whether a lane change is 'practicable' under heavy traffic. The statute does not prescribe objective tests (for example, a minimum clearance or a defined speed reduction), so training and local enforcement policies will determine how the terms are applied in practice.
The law’s breadth is both a strength and a complication. Covering any stationary vehicle using hazard lights or devices (cones, flares, retroreflective panels) extends protection to many roadside situations, but it also captures scenarios where moving over is unrealistic—narrow rural roads, single-lane highways, or divided highways where the stopped vehicle is on the opposite shoulder.
The exemption for vehicles 'not adjacent to the highway' or 'separated by a protective physical barrier' limits reach but leaves open questions about what counts as 'adjacent' and what configurations meet the 'protective barrier' test. Finally, the statute does not allocate resources for public education or signage, nor does it address liability where a required lane change precipitates a collision; those practical gaps will influence how agencies, contractors, and insurers respond.
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