After a crash between a car and a bike, fault is answered by the rules of the road, not by who was bigger or who was hurt. Our pedestrian and bicycle accident work starts from the rules instead. California gives a person riding a bicycle on a highway all the rights of a driver and makes them subject to the same rules of the road, except those that by their nature cannot apply (Vehicle Code 21200). The Vehicle Code also has rules written for bikes: how close a car may pass, who may use a bike lane, how a driver turns across one, and when a car door may be opened.
This guide explains how those rules decide fault, how fault is shared when both people made mistakes, and what changes the answer. Local roads matter too: in the state's 2023 crash rankings, Petaluma and Cotati both ranked among the higher rates in their size groups for bicyclists killed or injured, as the table further down shows.
How is fault decided after a car hits a cyclist, step by step?
- The facts are gathered. The police or CHP report, photos, video, witness names and the damage to the bike and the car show where each person was and what each did.
- Each person's conduct is compared with the rules. Did the driver pass too close, turn across the bike lane without merging into it, or open a door into traffic? Was the cyclist riding the wrong way, or without lights at night?
- A broken safety rule can create a presumption of negligence. If the rule was violated and the violation was a substantial factor in causing the harm, a jury must find negligence unless the violation is excused (CACI 418).
- Careless conduct counts even without a broken rule. Everyone must use ordinary care, and a person is responsible for injuries caused by a lack of it (Civil Code 1714(a)).
- Responsibility is divided by percentage. If more than one person's fault was a substantial factor, the jury assigns percentages that must total 100 percent (CACI 406).
- The cyclist's damages are reduced by their own share. If the driver proves the cyclist was negligent and that it helped cause the harm, the damages are reduced by the cyclist's percentage; the judge does the arithmetic (CACI 405).
Which traffic rules decide fault in a car and bike crash?
| Situation | The rule | Source |
|---|---|---|
| Passing a cyclist going the same way | The driver must pass at a safe distance and never closer than three feet; if another lane is available, the driver must change lanes to pass when practicable. If three feet is not possible, the driver must slow down and pass only when it will not endanger the cyclist. | Vehicle Code 21760 |
| Driving in a bike lane | A motor vehicle may be driven in a bike lane only to park where parking is allowed, to enter or leave the roadway, or to prepare for a turn within 200 feet of the intersection. | Vehicle Code 21209 |
| Turning across a bike lane | A driver who must cross an adjacent bike lane to turn has to drive into the bike lane before turning, and every turn must be made with reasonable safety and a signal. | Vehicle Code 21717 and 22107 |
| Turning left in front of a cyclist | A left-turning driver must yield to oncoming traffic close enough to be a hazard during the turn. | Vehicle Code 21801 (cyclists have a driver's rights under 21200) |
| Opening a car door | No one may open a door on the traffic side unless it is reasonably safe and will not interfere with moving traffic. | Vehicle Code 22517 |
| Where a slower cyclist rides | As close as practicable to the right edge, except when passing, turning left, avoiding hazards or a lane too narrow to share, or approaching a right turn. | Vehicle Code 21202 |
| Riding in a bike lane | A slower cyclist rides in the bike lane but may leave it to pass, turn left, avoid debris or hazards, or approach a right turn, after signaling when traffic may be affected. | Vehicle Code 21208 |
| Direction of travel | A bike on a roadway or shoulder must go the same direction as traffic. | Vehicle Code 21650.1 |
| Riding in the dark | A front white light visible from 300 feet, a rear red reflector or light visible from 500 feet, and pedal and side reflectors. | Vehicle Code 21201(d) |
What happens when the driver or the cyclist broke one of these rules?
A traffic law violation does not decide the case by itself, but it carries real weight. Under the jury instruction on negligence per se, if a person violated a safety law and the violation was a substantial factor in bringing about the harm, the jury must find that person negligent unless the violation was excused (CACI 418). The same instruction is written so it can be used against either side: a driver who passed at two feet faces it, and so can a cyclist riding against traffic.
The violation still has to matter to how the crash happened. A missing pedal reflector on a bike hit from behind at noon may have nothing to do with the collision. If the jury finds no violation, or finds that it did not help cause the harm, it still decides negligence under the ordinary standard of care, so a driver who technically gave three feet but swerved back too soon can still be found careless.
Citations at the scene are also only part of the picture. A violation of the three-foot rule is an infraction with a $35 fine, and $220 if the collision injured the cyclist (Vehicle Code 21760(e)). Whether a ticket was written does not decide the civil claim; the evidence does.
How do the rules apply to passing, turning and door crashes?
A car passes too close or clips the cyclist. The three-foot rule and the duty to pass at a safe distance apply (Vehicle Code 21760). The general passing rule also requires a driver overtaking another vehicle to pass on the left at a safe distance without interfering with it (Vehicle Code 21750). Mirror damage, paint transfer and where the bike came to rest can show how close the car was.
A right-turning car cuts across the bike lane. A driver turning right across a bike lane must first move into the bike lane, then turn, and must make the turn with reasonable safety (Vehicle Code 21717 and 22107). A driver who turns from the travel lane across a cyclist going straight has skipped that sequence.
A left-turning car crosses in front of an oncoming cyclist. A driver turning left must yield to oncoming traffic close enough to be a hazard (Vehicle Code 21801), and the cyclist has a driver's rights on the road. Our guide on right of way in left-turn and intersection crashes covers the signal and stop sign rules that also come into play.
A parked car's door opens into the cyclist. The rule against opening a door into traffic applies to any person, so a passenger who opens the door can be responsible as well as the driver (Vehicle Code 22517). Who opened the door, and whether they looked, matters.
A car drifts into the bike lane. Driving in a bike lane is allowed only to park, to enter or leave the road, or to prepare for a turn close to the intersection (Vehicle Code 21209). A driver using the bike lane to get around stopped traffic is outside those exceptions.
Where is a cyclist supposed to ride?
A cyclist going slower than traffic rides as close as practicable to the right edge, but the law lists exceptions: passing, preparing for a left turn, approaching a right turn, and avoiding hazards such as parked cars, debris, potholes or a lane too narrow for a car and a bike to share side by side (Vehicle Code 21202(a)). On a one-way road with two or more lanes, the cyclist may ride near the left edge instead (Vehicle Code 21202(b)). Riding in the middle of a narrow lane can therefore be lawful, and a driver who claims the cyclist should have hugged the edge may be wrong about the rule.
Where there is a bike lane, a slower cyclist uses it, with similar exceptions, and must signal before leaving it when traffic may be affected (Vehicle Code 21208). Bikes go with traffic, not against it (Vehicle Code 21650.1). Sidewalk riding is left to local ordinances (Vehicle Code 21206), so the answer depends on the city. Someone on an electric bike follows the same bicycle rules, with some extra ones explained in our guide on e-bike class, age and helmet rules in Sonoma and Marin.
What do the crash numbers show near Cotati and Petaluma?
The California Office of Traffic Safety ranks cities against others of similar size and counties against all 58 counties. In these rankings, 1 means the highest, or worst, rate in the group, and the office says rankings are only indicators of possible problems. Here are the 2023 figures for bicyclists killed or injured:
| Place (2023) | Bicyclists killed or injured | Rank (1 = highest) |
|---|---|---|
| Cotati (cities of 2,501 to 10,000) | 5 | 8 of 74 |
| Petaluma (cities of 50,001 to 100,000) | 22 | 16 of 103 |
| San Rafael (cities of 50,001 to 100,000) | 35 | 3 of 103 |
| Sonoma County (all roads) | 94 | 18 of 58 counties |
| Marin County (all roads) | 138 | 17 of 58 counties |
Our office is in Cotati, and the local offices for a crash there are on our page for injury cases in Cotati. For the police report and city claims process farther south, see our page on injury cases in Petaluma. Across the county line, our page for injury cases in San Rafael lists the Marin offices.
Who pays when the driver is at fault?
The driver's liability insurance is the first place to look for payment for the cyclist's medical bills, lost earnings and pain and suffering. If the driver had no insurance or too little, the cyclist's own auto policy may help even though they were on a bike; our guide on uninsured and underinsured motorist coverage explains how. If the driver left the scene, the reporting rules in our guide on hit-and-run crashes in Sonoma or Marin matter within the first day.
When a second driver, the owner of a car whose door opened, or a public agency also played a part, each one's share is measured separately. Our guide on who pays when several drivers are at fault explains how shares are paid.
What changes the answer?
The cyclist was a child. A child is held to the care a reasonably careful child of the same age, intelligence, knowledge and experience would use, not an adult's standard (CACI 402). Riders under 18 must also wear a helmet (Vehicle Code 21212). Our guide on injury claims for children explains the court approval a child's settlement needs.
It was dark. The lighting rules apply on a highway, sidewalk or bikeway in darkness (Vehicle Code 21201(d)). A bike without a front light may draw a fault argument; a driver who says they could not see still has to drive with care. The night-visibility questions are covered in our guide on being hit at night when the driver says they could not see you.
A pothole or road defect started the crash. A public entity can be responsible for a dangerous condition of its road (Government Code 835), and a written claim is due within six months (Government Code 911.2). See bike crashes caused by a pothole or road defect in Sonoma County.
The rider was on a scooter, not a bike. Motorized scooters have their own rules, including a 15-mile-per-hour limit. Our guide on e-scooter injuries and who is responsible covers them.
The cyclist was riding against traffic or on a sidewalk. Riding against traffic breaks Vehicle Code 21650.1, and sidewalk riding is allowed or barred by local ordinance (Vehicle Code 21206). Either can support a fault argument, but the driver still owed ordinary care (Civil Code 1714(a)), and the jury weighs both.
What could this look like? An example
For example, imagine a cyclist riding north in the bike lane on a Petaluma street at 5 p.m. in winter, with a front light and a rear reflector. A driver heading the same way speeds up to pass a bus, then turns right into a shopping center from the travel lane, crossing the bike lane without merging into it. The cyclist hits the side of the car and breaks a wrist.
The driver tells the officer the cyclist was going too fast. The rules point the other way: the driver had to move into the bike lane before turning and turn only when it was reasonably safe (Vehicle Code 21717 and 22107), and the cyclist was where the law says a slower rider belongs (Vehicle Code 21208). If the insurer argues the cyclist should have braked sooner, a jury could assign a small percentage to the cyclist, which would reduce, not erase, the recovery (CACI 405). The cyclist requests the report, keeps the bike unrepaired, and calendars the two-year deadline (Code of Civil Procedure 335.1). This example is made up to show how the rules fit together; it says nothing about any real case.
What mistakes do cyclists make after a crash?
- Repairing or throwing away the bike, helmet or clothing before they are photographed and inspected.
- Agreeing at the scene that they "came out of nowhere" when the rules gave them the lane.
- Assuming a missing citation means the driver was not at fault.
- Not asking nearby businesses for camera footage before it is recorded over.
- Giving the driver's insurer a recorded statement before reading the report.
- Missing the six-month claim deadline when a road defect was part of the cause.
What should I do this week?
- Get medical care and describe every symptom, including any blow to the head.
- Write down exactly where you were riding, where the car was, and what the driver said.
- Request the crash report; our guide on getting a crash report in Sonoma County lists the offices.
- Photograph the bike, helmet, lights, clothing and the scene, including lane markings.
- Ask nearby businesses to save video from the time of the crash.
- Report the crash to your own auto insurer if the driver's coverage may be too small.
- Calendar the deadlines; see California personal injury deadlines.
Frequently asked questions
Is the driver always at fault when a car hits a cyclist?
No. Fault follows the conduct of each person, and a cyclist who broke a rule that helped cause the crash can be assigned a share. That share reduces the recovery by its percentage rather than barring it (CACI 405).
Can I recover if I was riding without a helmet?
An adult on a regular bicycle is not required to wear one; the helmet law covers riders under 18 (Vehicle Code 21212), and every class 3 e-bike rider (Vehicle Code 21213). For a minor, or for a head injury, the other side may argue the missing helmet made the harm worse, and that argument goes to how responsibility is divided.
Was I allowed to ride in the middle of the lane?
It depends on the lane. The rule to keep right has exceptions for hazards and for lanes too narrow for a car and a bike to share side by side (Vehicle Code 21202(a)(3)).
Who is responsible for a dooring crash?
The person who opened the door when it was not reasonably safe (Vehicle Code 22517). That can be a passenger, and the driver may share responsibility depending on the facts.
How long do I have to file?
A lawsuit against a driver generally must be filed within two years (Code of Civil Procedure 335.1). A claim against a city, the County or the State is due within six months (Government Code 911.2).
Does the three-foot rule apply on narrow country roads?
Yes. If the driver cannot give three feet because of traffic or the road, the driver must slow to a reasonable and prudent speed and pass only when it will not endanger the cyclist (Vehicle Code 21760(d)).
If you were hit by a car while riding a bike, contact Young Law Group today at (707) 343-0556 or through our contact page for a free consultation.
Sources
- Vehicle Code section 21200 (cyclists have a driver's rights and duties)
- Vehicle Code section 21760 (Three Feet for Safety Act)
- Vehicle Code section 21750 (passing on the left at a safe distance)
- Vehicle Code section 21209 (motor vehicles in bike lanes)
- Vehicle Code section 21717 (turning across a bike lane)
- Vehicle Code section 22107 (turning with reasonable safety and a signal)
- Vehicle Code section 21801 (left turns: yielding to oncoming traffic)
- Vehicle Code section 22517 (opening doors into traffic)
- Vehicle Code section 21202 (where a cyclist rides on the roadway)
- Vehicle Code section 21208 (riding in a bike lane)
- Vehicle Code section 21650.1 (riding with traffic)
- Vehicle Code section 21201 (bicycle brakes, lights and reflectors)
- Vehicle Code section 21206 (local rules for bicycles)
- Vehicle Code section 21212 (helmets for riders under 18)
- Vehicle Code section 21213 (class 3 e-bikes: age and helmet)
- Civil Code section 1714 (duty of ordinary care)
- Code of Civil Procedure section 335.1 (two years for an injury)
- Government Code section 835 (dangerous condition of public property)
- Government Code section 911.2 (six-month claim to a public entity)
- Judicial Council of California: Civil Jury Instructions (CACI), 2026 edition: instructions 402, 405, 406 and 418
- California Office of Traffic Safety: Cotati crash rankings, 2023
- California Office of Traffic Safety: Petaluma crash rankings, 2023
- California Office of Traffic Safety: San Rafael crash rankings, 2023
- California Office of Traffic Safety: Sonoma County crash rankings, 2023
- California Office of Traffic Safety: Marin County crash rankings, 2023
- California Office of Traffic Safety: how the crash rankings work
