(A)   The speed limitations set forth herein shall not apply to authorized emergency vehicles when responding to emergency calls and the drivers thereof sound an audible signal by siren, bell or exhaust whistle capable of emitting sound audible under normal conditions from a distance of not less than 500 feet.
   (B)   This provision shall not relieve the driver of an authorized emergency vehicle from the duty to drive with due regard for the safety of all persons using the streets nor shall it protect the driver of any vehicle from the consequence of a reckless disregard of the safety of others.
('86 Code, § 18.230) Penalty, see § 70.99