South Dakota Administrative Rules
Title 70 - Department of Transportation
Article 70:01 - Administration - Highway Safety Signs and Notices
Chapter 70:01:02 - Speed limits
Section 70:01:02:00 - Interstate highways

(1) Interstate Highway 90 beginning at milepost 0.0 and ending at milepost 55.02, 75 miles per hour; then beginning at milepost 55.02 and ending at milepost 67.8 and beginning at milepost 394.6 and ending at milepost 403.19, 65 miles per hour;

(2) Interstate Highway 29 beginning at milepost 0.0 and ending at milepost 04.7, then beginning at milepost 72.72 and ending at milepost 85.25, 65 miles per hour;

(3) Interstate Highway 190 beginning at its intersection with State Trunk Highway 44, then north for 0.2 mile, 45 miles per hour; then north for 1.3 miles to the intersection with Interstate Highway 90, 60 miles per hour;

(4) Interstate Highway 229 northbound lanes beginning at milepost 0.0 (the junction with Interstate 29), then north to a point 0.5 miles south of the centerline of Interstate 90, 65 miles per hour;

(5) Interstate Highway 229 southbound lanes beginning at milepost 0.0, (the junction with Interstate 29), then north to the centerline of Interstate 90, 65 miles per hour; then north 0.25 mile to Minnehaha County Road 125, 55 miles per hour.

Each year from the Thursday preceding the first Friday in August through the second Sunday after the first Friday in August, the maximum speed limit is 65 miles per hour on the portion of Interstate Highway 90 beginning at milepost 28.9 and ending at milepost 55.02.