Not too long ago, many rental-car fleets were located within walking distance of the nation's airline terminals. Then space tightened up, and the rental operations moved farther away from the airport hub. To transport their customers from terminal to car, rental companies turned to the shuttle bus. Shuttle buses have become "moving billboards" - important, highly visible symbols of corporate identity.  "There are marketing benefits from the shuttles, no question about it," says Ken Bruno. manager of  national bus programs and special equipment for Avis Rent A car Systems, Inc. "And obviously, passengers will perceive the Avis image as it is reflected in our buses." Here's a look at what's available for 1985 in the  shuttle-bus market. Read the full article on 1985 shuttle buses, which ran in the December 1984 issue of AF.