Idaho Code § 40-1404A
In countywide highway districts located in a county with a population of more than two hundred thousand (200,000) persons in which the voters have chosen to establish a countywide highway district at a previous election, the county shall be divided by the county commissioners immediately upon the effective date of this act into five (5) subdistricts which shall be as nearly equal in population as practicable. No precincts shall be divided. A highway district commissioner shall be a resident of the subdistrict which he represents. Voters in each subdistrict shall vote only for one (1) candidate seeking to represent that subdistrict. County commissioners, mayors and city council members shall not be eligible to hold office as a countywide highway district commissioner. At the election held in 1998, commissioners representing subdistricts two and five shall be elected for two (2) year terms and commissioners representing subdistricts three and four shall be elected for four (4) year terms. Thereafter, all commissioners shall be elected for four (4) year terms. Any incumbent in office on the effective date of this act may complete the term to which they were elected and shall represent the subdistrict in which they reside. Any incumbent in office on the effective date of this act whose term expires on January 1, 2000, shall retain that office until January 1, 2000, shall be assigned the subdistrict in which they reside by the county commissioners, which subdistrict shall be numbered one as provided in this section and that commissioner need not stand for election in 1998.
A qualified voter of the countywide highway district shall be eligible to vote for a countywide highway district commissioner residing in the elector's subdistrict, and the election shall be conducted as provided by Idaho statutes relating to holding general elections at the county level.
The highway commissioners shall take office on January 1 of the year immediately following their election, and each may be compensated in accordance with the provisions of section 40-1314, Idaho Code, or receive a salary not to exceed one thousand two hundred dollars ($1,200) per calendar month with the exception of the president of the highway commissioners who may receive a salary not to exceed one thousand four hundred dollars ($1,400) per calendar month.
Idaho Code § 40-1404A