1- THE PROBLEM
Amongst the reasons underlying trains’ disasters, two are especially striking: (A) derailment, (B) trains’ crashes either due to derailed carriages, frontal shock or, paradoxically, to ‘backwards’ shocks.
Possible causes for derailment (excess of velocity, some objects on the rails, etc.) are here discarded. Rather, attention is paid to situations in which a driver is confronted either with eventual frontal shocks or (after a curve) with an unexpected stopped train.

2- A (POSSIBLE) SOLUTION
Both of these extreme situations could be solved if both drivers have an anticipated – or ‘virtual’ - image of the position of the other train - not only sufficiently far away to allow both the activation of an alarm signal (light or sound in the cabin) and of the emergency brakes (or, still whether possible, a direct action upon the trains’ motors).

In order to accomplish this, the solution proposed – which is valid for one or two lines - although this text is solely concerned with one single line - is depicted in Figs. 1,2,3. The main idea consists in considering the existence of two electric cables linking the starting and end stations of some region. One of this cables takes into account the motion of the real train, the other provides to the driver a virtual image of the position of some other undesirable train. Each cable is divided into several independent sections, serially numbered, so as depicted in Fig 2. Every section entails an Active Zone (activated via SRL, Fig. 1) and an Emergency/Safe Zone the length L of which depends on the velocity and inertia of the considered train - Right-Left in the case – being the Left-Right case a symmetric image of Fig.1. Its driver owns a visual ‘map’ providing not only his real position but also the virtual position of the eventual undesirable train, given by the second cable, an imaginary ‘mirror’ of the Right-Left cable. The activation of any of these sections (real and virtual) determines the Electric Image of the train’s position. This “Image” is transmitted via an Emitter to the real driver so that if no other section is activated then he can continue his course (“GREEN”, Fig. 3). Otherwise (situation “RED”) the Emitter sends alarms to both drivers or - if possible - acts automatically upon their emergency brakes.

3- COSTS
Practically restricted to the two emitters/receivers and to the needed switches and cables. Overall power supply for each one of the sections may be obtained from solar cells.