of 65 mph undivided highways are multiple stretches SR 22 surrounding the town of Dresden, where the road has two lanes in each direction (four lanes total), sometimes containing a central dual turn lane. U.S. Route 412 also contains a 60 mph four-lane undivided highway between Columbia and Hohenwald. Speed limits set by municipalities could range from 15 to 55 mph, depending on the type of roadway. This is because the state of Tennessee grants strong home rule powers to municipalities and Dillon's Rule for unincorporated areas in the county for speed limit assignments on non-controlled access state-maintained roads, requiring that they fall within established constraints. Out of Tennessee's of public road, a vast majority of are maintained by localities. In the 2000s, the major cities of Memphis, Knoxville and Chattanooga petitioned TDOT to enact environmental speed limits in their respective counties after failing to meet EPA air quality standards, reducing speed limits from 70 mph to 65 mph and 55 mph for trucks. Knox County (Knoxville) also petitioned the state to enact these speed limits in all of the neighboring counties of the Knoxville Metropolitan Area, as well as Jefferson County. These moves were controversial, as people believed the actual purpose was to increase revenue from speeding tickets, and the Tennessee Highway Patrol (THP) reportedly started enforcing these as 70 mph zones in the Knoxville area after multiple truckers successfully won court cases and had their tickets dismissed. In 2018, these split speed limits on I-75 and I-40 in Roane and Loudon counties southwest of Knoxville were increased back to 70. On February 19, 2019, 70 mph speed limit signs were installed on I-40 and I-81 east of Knox County starting at exit 398, and in October 2019, the last of these split speed limits were increased to 70 mph on I-40 east of Knoxville and to 65 mph west of Knoxville with no separate restrictions for trucks. In Nashville, speed limits for freeways are posted at 55 mph at the center of the city, and 65 and 70 mph beyond, with no separate restrictions for trucks. I-26 and I-81 in Kingsport, Bristol, and Johnson City continue with the staggered limits. Prior to 1974, the maximum speed limit on Tennessee's Interstate highways was day or night for cars and day or night for trucks. Other rural highways had a maximum speed limit of 65 mph day and night for