(1) A reduced incentive payment shall be made to any county or municipal county having appointed and employed either (a) a licensed county highway superintendent for only a portion of the calendar year preceding the year in which the payment is made or (b) two or more successive licensed county highway superintendents for the calendar year preceding the year in which the payment is made. Such reduced payment shall be in the proportion of the payment amounts listed in section 39-2503 as the number of full months each such licensed superintendent was appointed and employed is of twelve.

(2) Any county or municipal county that contracts for the services of and appoints a consulting engineer licensed under the County Highway and City Street Superintendents Act or any other person licensed under the act to perform the duties outlined in section 39-2502 rather than appointing and employing a licensed county highway superintendent shall be entitled to an incentive payment equal to two-thirds the payment amount provided in section 39-2503 or two-thirds of the reduced incentive payment provided in subsection (1) of this section, as determined by the Department of Transportation pursuant to section 39-2505.

(3) Any county or municipal county that contracts with another county or municipal county or with any city or village for the services of and appoints a licensed county highway superintendent as provided in section 39-2114 shall be entitled to the incentive payment provided in section 39-2503 or the reduced incentive payment provided in subsection (1) of this section.

(4) Beginning in calendar year 2022, any county or municipal county having a total population of sixty thousand or more inhabitants, as determined by the most recent official United States census, shall receive the full twelve-month Class A incentive payment amount provided in section 39-2503 applicable to such county's or municipal county's rural population as determined by the most recent federal census.

(5) Beginning in calendar year 2022, a county or municipal county having a total population of less than sixty thousand inhabitants, as determined by the most recent official United States census, may appoint and employ a professional engineer, who is licensed pursuant to the Engineers and Architects Regulation Act but is not licensed under the County Highway and City Street Superintendents Act, to perform the duties of county highway superintendent outlined in section 39-2502. In such case, the professional engineer's license under the Engineers and Architects Regulation Act shall serve as a Class A license for purposes of incentive payments under sections 39-2502 to 39-2505. This subsection only applies to a professional engineer in the direct employ of a county or municipal county and does not apply to an engineer serving as a contractor or consultant.