on South Dakotan rural freeways remain at or below the speed limit. In the urban areas of Sioux Falls and Rapid City, a 65 mph speed limit is posted on Interstates 90 and 29. In March 2015, SD State Legislature has passed the bill to raise the speed limit on Interstate 29 and Interstate 90 to . It was signed into law and took effect in April 2015. While the 80 mph speed limit was initially signed on all rural freeways in the state, the Interstate 90 stretch from Rapid City to the Wyoming Border returned to 75 mph due to safety concerns. Tennessee Tennessee statutes require rural interstates to be posted at exactly unless a traffic study is performed indicating that such a speed is unsafe. These include all of the state's two-digit Interstates except Interstate 55 and Interstate 26, whose highest posted speed limits for passenger vehicles in Tennessee is . The only auxiliary interstates in Tennessee with a 70 mph speed limit are Interstate 155, Interstate 269, and Interstate 840. 70 mph speed limits are required on other controlled access highways that are part of the State or Federal Highway Systems unless a traffic study indicates this speed is unsafe. Any other controlled access road in the state may be posted up to 70 mph, but this is not a legal requirement, and a study is not required to be performed before this is done. Examples of 70 mph limits are found on controlled-access portions of US 51 and SR 22, SR 111, SR 386, and SR 396. In 70 mph zones, the default minimum speed limit is 55. Urban interstates are generally posted at 55 to 65 mph, however, portions of Interstates 24, 40, and 65 and S.R. 386 in Nashville, as well as I-24 in Clarksville and Murfreesboro are posted at 70 mph. Four-lane divided highways in rural areas are normally posted at the statutory , although some are posted at and . It is a common misconception that undivided highways may only be posted up to in Tennessee. Though a vast majority of undivided highways have, at most, posted 55 mph speed limits, Tennessee's statutory speed limits do not differentiate between divided and undivided highways, per TN Code § 55-8-152(a) (2018), so the statutory limit of usually applies to undivided highways in the absence of signage or local ordinances to the contrary. Notable examples