Maintenance expense of the interstate system shall be from state highway funds. However, highway funds of counties, townships, and municipalities may be used in the maintenance of local service roads, overpasses, and underpasses constructed in connection with the interstate system, unless federal funds are made available for this purpose.

Source: SL 1955, ch 104, § 5; SDC Supp 1960, § 28.0235; SL 1963, ch 163; SL 2010, ch 145, § 58.