An interesting item from 1966 in Jon Gertner's book The Idea Factory: Bell Labs and the Great Age of American Innovation.
A Bell Labs project, paid for by the U.S. Department of Transportation, involved putting pay phones on the Metroliner, a new express train that would run between Union Station in Washington, D.C., and Penn Station in New York City. This was a simplified application of the cellular idea. The Metroliner route was divided into cells of different frequencies. Markers were put on the tracks—coils, actually—that could be tripped by the train as it passed; these signaled that a call had to be handed off from one cell, and one frequency, to another. “It was not great technology,” Frenkiel recalls, “but it was the first cellular system.”