Section 15308 Of Article 7. Sanctions From California Vehicle Code >> Division 6. >> Chapter 7. >> Article 7.

. (a) A driver shall not operate a commercial motor vehicle for a period of 120 days if the person is convicted of a serious traffic violation involving a commercial or noncommercial motor vehicle and the offense occurred within three years of two or more separate offenses of serious traffic violations that resulted in convictions.
  (b) Notwithstanding Section 13366.5, the time period under subdivision (a) shall not commence until all existing suspensions or revocations of the commercial driving privilege have ended.