The police department shall maintain a wrecker rotation list in alphabetical order which shall contain the names and addresses of each wrecker service operator who complies with the provisions of this chapter in order that said operator might be called upon for wrecker service by the police department in the absence of an expressed preference by the owner or operator of the vehicle requiring assistance. After the operator at the top of the list receives a call then that name shall be placed at the bottom of the list and the next operator shall be moved to the top of the list and he shall receive calls. This process shall be repeated until each operator providing wrecker service under the provisions of this chapter has received calls. The police department shall notify each wrecker operator in sufficient time prior to his rendering said wrecker service in order that the operator might adequately provide the necessary men and equipment to answer said calls.