In California, the pedestrian crossing lights have no legal standing, as far a enforcement. A pedestrian ALWAYS has the right of way at ANY intersection.
Technically, the pedestrian need not wait for a green "walk" sign, and, can legally cross against a red light.
It's tough on the drivers because they can't, simply rely on the pedestrian lights to tell them it's okay to procede or turn. However, my take is that a driver should not EVER rely on ANY traffic device to tell them it is safe to enter an intersection. The driver should ALWAYS pay attention to all traffic conditions.
Most don't understand that, by definition, "right of way" does NOT give a driver the right to occupy any particular piece of the roadway. "Right of way" ordinaces are written in such a way so as to determine who must YIELD the right of way. In other words, no one has the right to place themselves in front of a speeding car, no matter WHO has the "right of way."
Look at "Collin H"s answer. He actually states that if the pedestrian is already crossing, then it is safe to continue. There's no "magic" sheild that goes up, just because the pedestrian has the right of way. The second half of that crossing is just as hazzardous, if not more, than that portion under the green "walk" signal.
Certified Instructor, National Safety Council Defensive Driving Course 4