There has been a recent change in standards and legal requirements for establishing speed zones in California that affects all jurisdictions in the state. Upon the adoption of the 2003 MUTCD as amended with the California Supplement on May 20, 2004, the following language was incorporated in the California Supplement regarding speed limits:

"The speed limit should be established at the nearest 10 km/h (5 mph) increment to the 85th percentile speed. However, in matching existing conditions with the traffic safety needs of the community, engineering judgment may indicate the need for a further reduction of 10km/h (5 mph)." (California Supplement, p.51, last paragraph)

This is a change from the old Traffic Manual provision (replaced by the California Supplement) that allowed establishing a posted speed limit at the nearest 5 mph increment below the 85th percentile speed, and then allowing an additional 5 mph reduction for other traffic safety related considerations.

The new standard has already resulted in a legal challenge in Orange County where a Superior Court judge issued an opinion invalidating a citation issued on a street with a posted speed limit of 35 MPH where the 85th percentile was 44.2 MPH (Superior Court of California, County of Orange; People vs. Perez, Rebecca Dolores; Case No. FL727253; August 4, 2005). Referring to the above-mentioned section of the California Supplement, the court decided that the 85th percentile of 44.2 MPH should result in a posted speed limit of 45 MPH (nearest 5 mph increment) which then may be reduced by another 5 mph to a 40 MPH speed limit (based on written and documented engineering justifications). However, the involved jurisdiction had used the old language arriving at 40 MPH (5 mph increment below the 85th percentile speed), and then had even further reduced it by another 5 mph resulting in the posted speed limit of 35 MPH. The court, referring to the above-mentioned section of the California Supplement, found in favor of the defendant as in the judge's opinion the 85th percentile speed of 44.2 MPH should have been rounded to the nearest 5 mph increment which is 45 MPH, and then it might have been reduced another 5 mph using "documented" traffic safety consideration. However, in this case, the judge also raised concern that the involved jurisdiction had also failed "to show justification for the downward adjustments of more than 5 miles per hour as discussed in People v. Goulet 1992, 13 Cal App 4th Supp 17".

Although there is concern that this opinion might have failed to consider that the engineering and traffic survey (ETS) for this highway segment was done prior to May 20, 2004 (the date of adoption of the new California Supplement) and the new standards should not be required retroactively; nonetheless, it has raised awareness among municipalities about the new standards and legal requirements for establishing speed zones.

Bahadori.hamid@aaa-calif.com