No school bus shall be operated within the corporate limits of the city unless the bus is equipped with a suitable fire extinguisher, emergency flares, first-aid kit, replacement fuses, and an electric warning device, visual or auditory, in proper working order, by which the driver of the bus, while in driving position, may be made aware that the emergency door of the bus is not fully secured with all levers or handles fully engaged. The signal shall be operable whether the bus is stationary or moving. The bus must be heated to a reasonable degree of comfort.
('73 Code, § 74.30) Penalty, see § 77.99