I recently read a few posts about who is at fault if you are rear ended. There are many theories about this, but not many people who have an answer. So, with some generalities, here are some answers.
If you are driving in stop and go traffic, and traffic stops, you have an obligation to stop without striking the vehicle in front of you. If you do, you were following too closely, or you were driving too fast for conditions. The California Vehicle Code has rules, usually called the “rules of the road”, prohibits you from driving too fast for conditions in section 22350.
If you are driving and someone stops for no reason, you may not be at fault. However, you have an obligation to watch the road. So you may still be at fault.
The basic rule: drive at a speed so that you can stop if the vehicle in front of you stops. Its the safest way to avoid being at fault for a rear end accident – because the accident will not happen!