What is the test for establishing a new speed limit in a city?

As the trial court recognized, the enactment or amendment of a speed limit ordinance is not a ministerial act, but a legislative one involving the exercise of discretion. A necessary prelude to that legislative act is the completion and consideration of an engineering and traffic survey (Veh.Code, 22357). Absent legislative action by a city, the speed limit remains either as prescribed by Vehicle Code section 22352 or as previously established by ordinance under Vehicle Code section 22357. Whether and when the City should resort to the legislative process to establish or amend a speed limit is not addressed in the statute. The City's authority to decide whether and when to reevaluate an established speed limit implicates its legislative power and is not subject to review as a ministerial duty. (See Common Cause v. Board of Supervisors (1989) 49 Cal.3d 432, 442-443, 261 Cal.Rptr. 574, 777 P.2d 610.)