A transmitter at a lead vehicle transmits a first transmission signal
toward a first beacon and a second beacon associated with a following
vehicle. A data processor or estimator determines a first propagation
time associated with the first transmission and the first beacon and a
second propagation time associated with the first transmission and the
second beacon. A vehicle controller controls a heading of the following
vehicle to maintain a first distance substantially equal to a second
distance (i.e., first propagation time substantially equal to a second
propagation time) or a first distance that deviates from the second
distance by a predetermined maximum amount.