sentences:  I-55 provides an alternate route for motorists who do not want to take Interstates 240 and 40 through downtown to cross the Mississippi River.On January 18, 2008, the Federal Highway Administration authorized the states of Mississippi and Tennessee to extend I-69 from the I-40/TN 300 interchange in north Memphis to the I-55/I-69 interchange in Hernando; however, Tennessee has signed the extension of the route, although Mississippi has already done so.Interstate 55 is one of Tennessee's interstates where the speed limit is 65 MPH instead of 70.