70 mph limit, with 2 lane restricted to up to a 65 mph limit, and gravel roads have up to 55 mph limits. Roads within cities hold their own defined limits with 25 mph speed limits common in residential streets and 25-40 mph limits on urban 4-6 lane divided and undivided streets, with school zones at 15–25 mph. Northern Mariana Islands The speed limit in the Northern Mariana Islands is . Ohio The maximum speed limit found on highways in Ohio is on the Ohio Turnpike, Rural Freeways, and both the Expressway and Freeway portions of US 30 from Mansfield, Ohio to the Indiana State Line and US 33 from Wapakoneta to St. Mary's Ohio. The speed limit ranges from to on other divided highways. A small portion of the westbound lane (less than 500 feet) of State Route 16 in Licking County is signed at 70 MPH slightly before the route upgrades from a two-lane non-divided to a four-lane divided highway, but otherwise, no non-divided highway in the state currently has a speed limit higher than , though ODOT is now permitted to increase undivided roads to . Ohio is the only state east of the Mississippi River to allow 70 mph speed limits on non freeway roads. Both divided and non divided roads qualify. Ohio has an urban speed limit of on Interstates by state law, yet many urban areas have lower speed limits due to safety concerns found in speed studies. These commonly are in the 50–60 mph range. For instance, in most of metro Dayton and Cincinnati, as well as in downtown Columbus, the speed limit is , while in Cleveland, Toledo, and Akron the speed limit is ; however, in central Cleveland along the Inner Belt, the speed limit is . On one case, however, the Ohio Turnpike has a limit in the outer suburbs of Toledo, Akron, and Cleveland. Some urban areas are also posted with minimum speed limits, usually with a minimum of 40 or 45. At one time, portions of Interstate 76 and Interstate 77 in downtown Akron had a maximum speed limit of 50 mph and a minimum speed limit of 35 mph. School zones in Ohio normally have a 20 mph speed limit, regardless of the road's normal speed limit, in effect during school hours. Oklahoma In Oklahoma, the maximum posted speed limit is 75–80 miles per hour on turnpikes