Quick answer
Common causes include speeding, distracted driving, impaired driving, unsafe turns and failure to yield, following too closely, and unsafe lane changes. Each one violates a specific Vehicle Code section, and under Evidence Code section 669 a proven violation that caused the injury creates a presumption that the driver failed to use due care. The other driver can still try to rebut it.
Common causes of car accidents in California include speeding, distracted driving, impaired driving, unsafe turns and failure to yield, following too closely, and unsafe lane changes. In an injury claim the label matters less than the statute behind it. Each behavior violates a specific Vehicle Code section, and under Evidence Code section 669 a proven violation creates a rebuttable presumption that the driver failed to use due care. Which section applies, and what proves it, is the whole game.
We are B&D Law Group, APLC, and our team handles car, motorcycle, and pedestrian injury claims across California and in Las Vegas, Nevada. For each cause below we name the governing section, the evidence that proves a violation, and the problem the other side raises. Adjusters rarely argue about what a crash looked like. They argue about proof.
How a Traffic Violation Becomes Proof of Negligence
California calls this negligence per se, and it lives in Evidence Code section 669. Subdivision (a) sets four elements: the person violated a statute, ordinance, or regulation of a public entity; the violation proximately caused death or injury; the injury was of the nature the statute was designed to prevent; and the injured person was in the class the statute protects.
Meet all four and the driver’s failure to exercise due care is presumed, but presumed is not established. Subdivision (b) lets the driver rebut by proving he or she did what might reasonably be expected of a person of ordinary prudence, acting under similar circumstances, who desired to comply with the law. The doctrine shifts work onto the defendant; it does not end the case.
A ticket is also not the violation, and neither is a conviction: Vehicle Code section 40834 provides that a judgment of conviction is not res judicata and creates no collateral estoppel in a later civil action. It must be proven independently.
Speeding: Two Statutes, Two Fights
| Crash cause | California Vehicle Code | What it requires |
|---|---|---|
| Driving too fast for conditions | § 22350 | Speed reasonable and prudent for conditions |
| Exceeding the maximum speed | § 22349 | 65 mph; 55 on two-lane undivided highways |
| Holding a phone while driving | § 23123.5 | No holding and operating a handheld device |
| Talking on a handheld phone | § 23123 | Wireless telephone must be hands-free |
| Driving under the influence | § 23152 | No driving impaired or at 0.08 percent BAC |
| DUI causing injury | § 23153 | DUI plus an unlawful act that injures another |
| Unsafe left turn or U-turn | § 21801 | Yield to oncoming vehicles posing a hazard |
| Failure to yield at a stop sign | § 21802 | Stop, then yield to an immediate hazard |
| Failure to yield to a pedestrian | § 21950 | Yield in marked and unmarked crosswalks |
| Following too closely | § 21703 | No following more closely than is prudent |
| Unsafe lane change or turn | § 22107 | Move only when safe, and after signaling |
Most people picture the posted limit, section 22349: no more than 65 miles per hour, and no more than 55 on a two-lane undivided highway unless posted higher after an engineering and traffic survey.
The section that decides more cases is 22350, the basic speed law: no person shall drive at a speed greater than is reasonable or prudent having due regard for weather, visibility, the traffic on, and the surface and width of, the highway, and in no event at a speed which endangers persons or property. A driver doing 55 in fog on a wet freeway can violate 22350 without touching the posted limit. Because reasonable and prudent is a jury question, we build it from conditions evidence and event data recorder downloads.
Distracted Driving After People v. Porter
Two sections govern. Section 23123 prohibits driving while using a wireless telephone unless it is designed and configured for hands-free listening and talking and used that way. Section 23123.5 is broader: no driving while holding and operating a handheld wireless telephone or electronic wireless communications device. Subdivision (c) carves out a mounted device operated with a single tap or swipe.
What counts as operating a phone was unsettled until recently. In People v. Porter, a published Sixth District Court of Appeal decision filed June 3, 2025, the court held that operating under section 23123.5(a) reaches all uses of a handheld phone’s functions, including looking at a mapping application.
Section 12810.3 adds a violation point for a conviction under section 23123(a), 23123.5(a), or 23124(b) occurring on or after July 1, 2021 within 36 months of a prior conviction for the same offense. The National Highway Traffic Safety Administration reports on its distracted driving page that 3,208 people were killed in crashes involving distracted drivers nationwide in 2024. Proving distraction civilly means moving fast for carrier records and the handset, because message, app, and screen wake timestamps line up against the crash time.
Impaired Driving and the Wall at the Bar
Section 23152 makes it unlawful to drive under the influence of an alcoholic beverage, to drive with 0.08 percent or more of alcohol by weight in the blood, to drive under the influence of a drug, or to drive under their combined influence; commercial drivers and drivers carrying passengers for hire are held to 0.04 percent. Section 23153 is the injury statute: impairment plus concurrently doing an act forbidden by law or neglecting a driving duty that proximately causes bodily injury to someone other than the driver. It therefore builds in a second violation.
Families are most often surprised by the bar. Business and Professions Code section 25602(b) says a person who furnishes alcohol in violation of subdivision (a) is not civilly liable for injuries resulting from the consumer’s intoxication, and subdivision (c) declares consumption rather than service the proximate cause. Narrow exceptions exist, covered in our post on California dram shop law. Per the California Office of Traffic Safety score card, alcohol-impaired driving deaths fell from 1,419 in 2022 to 1,355 in 2023.
Unsafe Turns and Failure to Yield
Section 21801(a) requires a driver turning left or completing a U-turn to yield to all vehicles approaching from the opposite direction that are close enough to constitute a hazard at any time during the turning movement, and to keep yielding until the turn can be made with reasonable safety. Subdivision (b) flips that duty once the driver has yielded and signaled, and defense counsel lives there.
At stop signs, section 21802(a) requires a driver to stop as required by section 22450 and then yield to vehicles close enough to be an immediate hazard; subdivision (c) makes it inapplicable where every approach is signed, which is why four-way stops differ. Section 21950(a) requires yielding to a pedestrian in any marked crosswalk or unmarked crosswalk at an intersection.
These cases turn on angles and timing, not documents. Intersection cameras, business surveillance, transit video, and the point of impact decide right of way, and that footage is overwritten within days.
Following Too Closely and Unsafe Lane Changes
Section 21703 states that a driver shall not follow another vehicle more closely than is reasonable and prudent, having due regard for the speed of that vehicle and the traffic upon, and the condition of, the roadway. There is no numeric distance, which cuts both ways. Proof comes from closing speed, skid marks, and braking data in the following vehicle.
Section 22107 covers lane changes: no person shall turn a vehicle from a direct course or move right or left upon a roadway until the movement can be made with reasonable safety, and then only after an appropriate signal if any other vehicle may be affected. Those are two requirements, so a driver who signals but merges into an occupied lane still violates the section. Sideswipe damage and paint transfer establish who crossed the line. We addressed changing lanes inside an intersection separately.
Why More Than One Cause Can Share the Blame
Most serious crashes have more than one cause, and California handles that with pure comparative fault. In Li v. Yellow Cab Co. (1975) the California Supreme Court abolished contributory negligence and held that damages are diminished in proportion to the negligence attributable to the person recovering. Pure means no cutoff: a driver 70 percent responsible still recovers 30 percent.
So naming a second cause rarely hurts you. A speeding driver, a distracted driver, and a poorly maintained roadway can share one verdict form. An adjuster who says your own conduct bars your claim is describing a rule California abandoned fifty years ago. Deadlines bind harder: Code of Civil Procedure section 335.1 gives two years from the date of injury, and a public entity claim carries a six-month written claim requirement.
Frequently Asked Questions
What is the single most common cause of car accidents in California?
The California Office of Traffic Safety reports 4,061 traffic deaths in California in 2023, of which 1,355 involved alcohol-impaired driving. For your claim the statistics matter less than the fit between the driver’s conduct and a specific Vehicle Code section.
Does a traffic ticket prove the other driver was at fault?
No. Vehicle Code section 40834 provides that a judgment of conviction for a Vehicle Code violation is not res judicata and creates no collateral estoppel on any issue in a later civil action. A citation shows how the investigating officer read the scene, but the violation still has to be proven in the civil case.
Can a driver be at fault for speeding while under the posted limit?
Yes. Vehicle Code section 22350, the basic speed law, forbids driving faster than is reasonable or prudent having due regard for weather, visibility, traffic, and the surface and width of the highway. Rain, fog, glare, or heavy congestion can make a lawful posted speed unreasonable, and that is a jury question built from conditions evidence and vehicle data.
Is holding a phone to look at a map illegal in California?
In People v. Porter, a published Sixth District Court of Appeal decision filed June 3, 2025, the court held that operating a handheld phone under Vehicle Code section 23123.5(a) covers all uses of the phone’s functions while driving, including viewing a mapping application. Section 23123.5(c) still permits a mounted device operated with a single swipe or tap.
Can I still recover if the crash was partly my fault?
Usually yes. Under Li v. Yellow Cab Co. (1975) California applies pure comparative fault, so damages are reduced in proportion to your share of the negligence rather than barred, with no percentage cutoff. Your deadline is generally two years under Code of Civil Procedure section 335.1, or six months to present a written claim if a public entity is involved.
The sooner someone identifies the governing Vehicle Code section, the sooner the right evidence is preserved. We handle car accident, motorcycle, and pedestrian accident claims. Call (888) 977-2238 or use our contact page.
This article is provided for general informational purposes only and does not constitute legal advice. Reading it does not create an attorney-client relationship. Every case is different and past results do not guarantee a similar outcome. If you have been injured, speak with a licensed attorney about your specific situation.