What Factors Should Be Considered by the State In Order to Determine Whether to Install a Traffic Control or Safety Device or Not ? In Alvarez v. State of California (1999) 79 Cal. App. 4th 720 95 Cal. Rptr. 2d 719, the court discussed how the State determines when median barriers are warranted, as follows: Median barriers result in a trade-off. They prevent nearly all cross-median accidents, but usually result in an overall increase in accidents and injuries. A median barrier is a fixed object which, when hit, can cause serious injury either by direct impact or by deflecting vehicles back into traffic. In addition, a barrier eliminates half the recovery area for out-of-control vehicles. Based on studies of the effectiveness of median barrier placement, California has developed a median barrier policy. The policy reflects the fact that as traffic volumes rise, the chance that an errant vehicle will cross the median and strike an opposing vehicle increases. But as the median reaches a certain width, it is less likely that those events will occur. With medians 46 feet or wider, regardless of traffic volume, the benefits of preventing cross-median accidents and injuries by barrier placement are outweighed by the disadvantages of the accidents and injuries generated by a barrier. The only exception to this rule is at those locations where there is a demonstrable history of excessive cross-median accidents: an accident rate of 0.12 fatal or 0.50 total cross-median accidents per mile per year. "The State policy--median barriers should be installed on freeways only if the result of striking the barrier is less severe than the result if no barrier existed--is reflected in median barrier warrants. There are two types of warrants, traffic volume/median width warrants (traffic volume/width warrants) and accident warrants. Traffic volume/width warrants index traffic volume to median width. Accident warrants index the frequency and severity of traffic accidents at a given locale with a state average. the California Department of Transportation (CalTrans) Traffic Manual described 'warrants' as follows: 'Warrants provide guidance to the engineer in evaluating the potential safety and operational benefits of traffic control devices and are based upon "average" or "normal" conditions. Warrants are not a substitute for engineering judgment. The fact that a "warrant" for a particular traffic control or safety device is met is not conclusive justification for the installation of the device. The unique circumstances of each location and the amount of funds available for highway improvements must be considered in determining whether or not to install a traffic control or safety device.' " ( Alvarez v. State of California, supra, 79 Cal. App. 4th at pp. 724-725.)