There are rental companies on-site in the garage at OKC's terminal. I know Thrifty is there and I suspect Hertz is as well. The National/Alamo location is on Meridian Ave., which is the street that leads from the freeway to the airport, so it is a straight shot and there aren't many stoplights along the way. It is still a bit of a hoof; I thought it was telling that we passed a Hertz Local Edition before we got to the National lot.