Vehicle Code section 21658

Whenever any roadway has been divided into two or more clearly marked lanes for traffic in one direction, the following rules apply:

(a)

A vehicle shall be driven as nearly as practical entirely within a single lane and shall not be moved from the lane until such movement can be made with reasonable safety.

(b)

Official signs may be erected directing slow-moving traffic to use a designated lane or allocating specified lanes to traffic moving in the same direction, and drivers of vehicles shall obey the directions of the traffic device.

Source: Section 21658, https://leginfo.­legislature.­ca.­gov/faces/codes_displaySection.­xhtml?lawCode=VEH§ionNum=21658.­ (updated Jan. 1, 1975; accessed Jun. 18, 2026).

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Verified:
Jun. 18, 2026

§ 21658's source at ca​.gov