A tractor trailer travels in the northbound lane of Missouri 71 Highway, soon to be renamed I-49, near Carthage, Mo., Wednesday morning, Feb. 23, 2012. New mile marker signs are being installed as the state highway is being transformed into an interstate. (AP Photo/The Joplin Globe, T. Rob Brown)
A tractor trailer travels in the northbound lane of Missouri 71 Highway, soon to be renamed I-49, near Carthage, Mo., Wednesday morning, Feb. 23, 2012. New mile marker signs are being installed as the state highway is being transformed into an interstate. (AP Photo/The Joplin Globe, T. Rob Brown)
A tractor trailer travels in the northbound lane of Missouri 71 Highway, soon to be renamed I-49, near Carthage, Mo., Wednesday morning, Feb. 23, 2012. New mile marker signs are being installed as the state highway is being transformed into an interstate. (AP Photo/The Joplin Globe, T. Rob Brown)