The speed limitations set forth in sections 169.14 to 169.17 do not apply to an authorized emergency vehicle responding to an emergency call. Drivers of all emergency vehicles shall sound an audible signal by siren and display at least one lighted red light to the front, except that law enforcement vehicles shall sound an audible signal by siren or display at least one lighted red light to the front. This provision does not relieve the driver of an authorized emergency vehicle from the duty to drive with due regard for the safety of persons using the street, nor does it protect the driver of an authorized emergency vehicle from the consequence of a reckless disregard of the safety of others.