In regards to car accidents, California has comparative negligence laws. It's important for drivers and passengers to understand how these work and how they can divide fault up between multiple parties.
Essentially, these laws can assign a percentage of blame to a specific person, and this blame can be divided between numerous people who were involved to one degree or another. This is vastly different than simply picking one party who was completely responsible. It even means that passengers, in rare situations, could be held responsible for causing accidents, despite not being behind the wheel.
For example, perhaps a car coming toward you is being driven by a man on his way to work. He's carpooling with a female coworker to save money, and they're slightly speeding since they're running behind. She is drinking her morning cup of coffee on the ride in.
Carelessly, she sets the coffee cup on the center console with a loose lid. She then turns in her seat and bumps it with her elbow, knocking it into the man's lap. He's burned, loses control of the car, crosses the center line and hits you.
You did nothing wrong, and that opposing driver is responsible since he was speeding and lost control of his vehicle. However, comparative negligence laws could determine that the woman was 50 percent responsible for spilling the coffee and setting off the chain reaction of events.
In a case like that, you may be able to seek compensation from both the passenger and the driver. It's critical that you know what legal rights you have and how the determination of fault sets up your next steps.
Source: FindLaw, "Who Is Liable in a Carpool Accident?," Edward Tan, accessed Sep. 28, 2017