In this case, where motorists are looking to pedestrian signals to decide whether or not they can increase speed to beat a light, and rear-ending another in the process, the liability is obviously with the motorist. Pedestrian signals are in place exclusively for the management of sidewalk-to-sidewalk traffic. At no place in law, MUTCD, or HDM does it suggest otherwise. Thus, the motorist is at fault if s/he uses a pedestrian signal to measure how to drive an automobile on the road and, in doing so, causes harm to person or property.
Moreover, California Vehicle Code 21703 explicitly states: "The driver of a motor vehicle shall not follow another vehicle more closely than is reasonable and prudent, having due regard for the speed of such vehicle and the traffic upon, and the condition of, the roadway." That's the citation to resolve the rear-ending issue. Increase the fine, advertise it well, and watch these kinds of collisions go down.
But that's not even the underlying problem. The underlying problem is that there is an over-inflated value of life and convenience placed on the motor vehicle and driver in comparison to all others using the public right of way. This is why the pedestrian signal is being blamed for the issue, not the motorists themselves.
Drivers of motor vehicles notoriously go un-cited for killing bicyclists and pedestrians in the course of violating traffic law and, recently, some people are picking up on the pattern.
Moreover, the last 4 decades of city design have seen the expectation of free right turns and super-wide right turns-- both of which make traveling by automobile faster and more convenient, but also increase the amount of time it takes for a pedestrian to cross a road. With the increased crossing time requirements, it becomes more and more necessary to have countdown timers on pedestrian signals.
If you want an engineering solution to this problem, implement the 3 engineering change below:
(1) Tighten up corners to at intersections. This reduces the distance corner-to-corner, reduces the time needed to cross the street, and slows down automobiles so that they actually see the pedestrians crossing the street (http://safety.fhwa.dot.gov/intersection/signalized/13027/images/e91.png).
(2) Add pedestrian bulb-outs wherever there is street parking to further reduce the time needed to cross the road. (http://www.ci.richmond.ca.us/images/pages/N2674/Bulb%20Outs.jpg)
(3) Then, and only then, remove the count-down timer for pedestrian signals at that intersection.
(1) The right-turning automobile is slowed, but red signal durations become shorter because it takes less time for pedestrians to cross the street.
(2) Pedestrians cross the street quicker.
(3) Pedestrians count-downs are removed due to lack of need thus removing the temptation from motorists to use them inappropriately.