South Dakota has a series of speed limits depending on your location.
- The speed limit on Interstate 29 and Interstate 90 is 75 mph for cars or trucks, day or night, with a minimum speed of 40 mph.
- All South Dakota secondary highways are 65 mph, unless otherwise posted.
- South Dakota's school zones and obstructed intersections are 15 mph.
- City streets in South Dakota are 25 mph, unless otherwise posted.
Of course, all vehicles traveling in South Dakota are required to operate in a reasonable and prudent manner based on the existing driving conditions.