The driver of a vehicle upon a street or highway within the city, upon meeting or overtaking from either direction any school bus which has stopped on or adjacent to any street or highway for the purpose of receiving or discharging any schoolchildren and other occupants and on which the red loading signals are in operation, is to stop his or her vehicle before reaching the school bus and not proceed until the loading signals are deactivated and then proceed past such school bus at a speed which is reasonable and with due caution for the safety of such schoolchildren and other occupants, and this section shall be applicable only in the event the school bus shall bear upon the front and rear thereon a plainly visible sign containing the words "School Bus" in letters not less than eight inches (8") in height. (2002 Code § 10.08.420)