California Code, Vehicle Code - VEH § 40000.28

Any offense which would otherwise be an infraction is a misdemeanor if a defendant has been convicted of three or more violations of this code or any local ordinance adopted pursuant to this code within the 12-month period immediately preceding the commission of the offense and such prior convictions are admitted by the defendant or alleged in the accusatory pleading.  For this purpose, a bail forfeiture shall be deemed to be a conviction of the offense charged.

This section shall have no application to violations by pedestrians.