
“The first Space Shuttle vehicle destined to fly in space moves toward Pad A at Launch Complex 39 where it will be launched. The STS-1 vehicle, consisting of America’s first reusable spaceship - the Orbiter Columbia, an external propellant tank and two solid rocket boosters, was assembled on a Mobile Launcher Platform in the Vehicle Assembly Building. A six-million pound tractor, called the Crawler-Transporter, is used to carry the Space Shuttle from the VAB to the launch pad, some 3.5 miles away.”
A simpler, more trusting and I suppose, naïve time...I believe that's a TWA Services tour bus, directly in the path of the shuttle stack, immediately at the start of the incline up to LC-39A.