features the principal object of the present invention is to overcome these disadvantages and provide an anti-collision safety device for vehicles travelling on tracks, without any driving personnel, that is to say, a device which itself can estimate risks and react in consequence. more generally, the invention is intended to provide a device comprising means of observation and making decisions for safe operation, using in particular the principle of deformable movable blocks. benefits of acd  very economical and cost effective.  easily adaptable and expandable.  does not degrade the existing safety level.  employs state-of-art hardware and software technology.  no way had side equipment required, hence no requirement of power.  no cabling on the track required (which is more expensive and cumbersome).