SINGLE COUNTYWIDE HIGHWAY DISTRICTS – Amends existing law to revise provisions regarding the election of commissioners in certain single countywide highway districts.

S 1229 revises election rules for countywide highway district commissioners in Idaho counties with over 200,000 residents. It requires these counties to divide into five population-equal subdistricts, with commissioners elected by residents of their specific subdistrict (replacing at-large voting). The bill establishes 4-year terms for all commissioners after 1998, adds primary elections for these positions starting in 2026, and clarifies write-in candidate requirements for highway district offices. This directly affects voters and potential candidates in eligible Idaho counties with highway districts.