Many people think that traveling the speed limit is the best speed to drive when driving on the freeway or city streets. However, if you get involved in an auto accident, your speed will be in an issue. Driving the "speed limit" is not a defense to driving too fast. Technically, you can drive the speed limit and still be guilty of driving too fast. California's basic speed law (Vehicle Code Section 22350) does not say anything about the speed limit. California's basic speed law says that you must drive at the speed that is reasonable for the circumstances. Therefore, even if the speed limit is 55 mph, that does not mean you can drive 55 mph if there is traffic or stoppage in other lanes etc. When it comes down to it, California's driving law requires a driver to be "reasonable" which doesn't necessarily mean driving the speed limit.
Back when I was a defense lawyer (defending personal injury cases for a major insurance company), I once had a case once where my client mistakenly turned left into oncoming traffic. There were three lanes in the opposite direction and cars in the #1 and #2 lanes stopped for him. The other party was driving the speed limit (35 mph) in the #3 lane and hit him while he was turning. While my client should not have turned, we did get the jury to find the other vehicle's driving to be 30% at fault for driving too fast. We argued that since cars were stopped in the #1 and #2 lanes, she should have realized something was going on and driving the speed limit could not be used as an excuse. Arguably, we had a steep hill to climb with such an argument, but the argument worked in that case.
California Vehicle Code section 22350 is known as the basic speed law. You need to drive a “reasonable” speed for the circumstances. The fact you were driving the speed limit is not, in itself, a defense. The posted limit is the MAXIMUM speed but not necessarily the “reasonable” speed.
I had a case a few years ago where I represented a gentleman who was turning left at an intersection. It was one of those cases where vehicles in the opposite lanes stopped to allow him to turn due to congestion. A woman driving in the opposite direction in the curb lane was driving 35 mph and slammed into my client as he was making his left. His vehicle flipped over twice due to the speed of the impact.
She brought suit against him arguing that he made an unsafe lane change. While she was probably correct, we were able to convince a jury that she was also driving too fast. She countered that she was driving the “speed limit.” However, we convinced the jury that the basic speed law says you must drive a “reasonable” speed under the circumstances. If all vehicles to your left have come to a stop, there must be a reason, and continuing to drive the maximum speed limit of 35 was probably imprudent. The jury found her 35% at fault for the accident.