1. A computer controlled train collision avoidance and warning system; the system comprising: at least one satellite in communication with at least one Global Positioning System device providing a first communication link between the at least one satellite to determine a location of at least a first train; a second communications link allowing communications between at least one fixed station and at least a first said train; wherein said second communications link provides continual communications between said at least one fixed station and at least one of a potentially unlimited number of other trains; wherein, said first communications link provides a location of any one said trains and said second communications link provides a location of one train relative to at least one other train via processing means in each said at least one train; wherein, each said fixed stations are located at a known position on a rail track and at a predetermined distance from each other; wherein, each said fixed station includes a transponder which emits a range signal to said processing means in each train for track identification; and wherein each fixed transponder station further emits correction signals for correcting errors in Global Positioning System signals from said first communications link to enable determination of exact track separation of trains on a track network allowing for respective train lengths and track curvature.