USC Engineering Student’s Term paper Sheds Light on Palisades Drive
James Carchich, is a student at the Viterbi School of Engineering at USC. Just a few short months ago James chose Palisades Drive, as a subject for his term paper on Human Factors and Safety. The paper is well documented and worth a look. LADOT might well be advised to ping young Mr. Carcich for his considerable experience on Palisades Drive.
The paper is filled with technical insights into the issues, but powerfully ends with a bit of commentary… “Human factors are present everywhere, and safety issues are abundant. However, as with the accidents, it takes human influence to make any changes occur. The need for change must be pushed forward and imposed upon those in charge. Every time there is an accident and/or death, people complain that changes must be made; yet when it comes time to take action, nothing is done.”
- Good Work James
Download the paper here. (312K PDF)
With all due respect to Mr. Cachich, his paper is more of an impassioned editorial than a serious engineering study. As an example, his discussion of speed limits displays a fundamental misunderstanding of traffic engineering and the law.
One reason that drivers exceed the speed limit on Palisades Drive is that the limit is set artificially low. California law requires that speed limits be set at the 85th percentile of traffic speeds (the “critical” speed), and that speed limits set below that, unless justified by other factors, are a speed trap. Cal. Veh. Code 627, 40800-40805. The following pamphlet, available on the Cal DOT website, explains traffic zoning procedures, and the 85th percentile rule. http://www.dot.ca.gov/dist05/traffic/Realistic-Speed-Zoning.PDF
The theory behind the 85th percentile rule is that drivers will naturally find their safe speed on a roadway and tend to travel at that speed. The top 15 percent is discarded as being those drivers who will tend to exceed safe limits (certainly, some of the performance cars driven in the Palisades Drive canyon well exceed the 85th percentile). This website has a compilation of speed limit studies that bear out the safety of setting speed limits at the 85th percentile. http://www.motorists.org/speedlimits/home/speed-limit-studies/
For years, the Palisades Drive canyon was unenforceable by radar because the engineering study observed that the critical speed was higher than the 45 mph limit. More recently, the traffic survey was amended to justify the 45 mph speed limit, even though nothing in the canyon had changed.
Increasing the speed limit to the critical speed, and then stepping up enforcement, would likely provide added safety to those using Palisades Drive. This change would have minimal cost, and can be easily implemented. It would eliminate any enforcement issues caused by setting the speed limit below the critical speed, and would provide drivers with a realistic speed limit to obey. I realize that most people reading this will dismiss the idea of actually raising the speed limit as preposterous, but traffic studies show that it can actually increase safety, which is what this website is all about.
Other measures to increase safety also have merit. The reflective lane markers, installed after the 2007 fatality, were a dramatic improvement in illuminating the canyon roadway at night. Mr. Cachich’s idea of installing plastic lane dividers would certainly add safety by discouraging drivers from crossing the center divider, but they may be cost prohibitive to install and maintain. Certainly, similar dividers on PCH require frequent replacement from being hit by errant drivers. But if the plastic dividers were installed only on the curves, where most motorists tend to cross over, it might be economically feasible.
Bicycle safety is more difficult to implement. Contrary to Mr. Cachich’s paper, riding in the roadway is perfectly legal, unless prohibited by local regulation. Cal. Veh. Code 21200-21212. Certainly, riding on the sidewalk is likely a safer option, but bicycles specifically made for road riding may not be able to withstand the rough and uneven pavement of the present sidewalk. In addition, bicycles on the sidewalk impede (and endanger) pedestrians. Installing a bike lane on either the road or the sidewalk would cost a great deal of money, and is not likely feasible during our present budget crisis. There appears to be no easy solution to this problem.
There actually are not any sidewalks in the canyon. There are shoulders that are used by pedestrians as sidewalks, and bicyclists as bike paths. Calling them sidewalks is part of the issue.