Conductor rail for transmitting electric energy to a train, comprising: - a main body made of high conductivity aluminum alloy, including an upper head portion, a stem portion and a lower base portion, - a facing cap made of stainless steel, on which a conductive shoe is adapted to slide, said facing cap comprising a central portion adapted to lay against a top surface of the upper head portion and two lateral portions (42, 44) arranged against lateral sides (242, 244) of the upper head portion and welded to the central portion so that the facing cap is secured to the main body, the lateral edges (402, 404) of the central portion extending in the alignment of the lateral sides (242, 244) of the upper head portion, each lateral portion (42, 44) having a transversal J-shape having a substantially constant thickness and including a straight section (420, 440) laying against a lateral side (242, 244) of the upper head portion, and a curved section (422, 442) having a first side, a second side and an end side connecting said first and second sides, the main body comprising two longitudinal grooves provided on an intersection area between the head portion and the stem portion below the top surface of the upper head portion, and in which the curved sections (422, 442) of the lateral portions (42, 44) are inserted, wherein the shape of the area extending between the lateral sides (242, 244) of the upper head portion and the grooves is complementary to the shape of the lateral portions (42, 44) of the facing cap, wherein the grooves are inclined downwardly with respect to a central symmetry plane of the main body passing through the upper head portion, the stem portion and the lower base portion and with respect to which plane said two lateral portions (42, 44) are mounted symmetrically, and wherein the grooves have an upper lateral side laying against said first side of the curved section (422, 442), a second lower lateral side, an inner bottom side connecting said upper and lower lateral sides, and an outer open side which is opposite to the inner bottom side and is oriented towards a lower side of the main body and away from said central plane of the main body, characterized in that the longitudinal grooves are broader than the curved sections (422, 442) of the lateral portions (42, 44) and each groove is defined to set at least a space between the inserted ending of the curved section (422, 442) and the groove, wherein said outer open side is wider than said inner bottom side, the grooves further comprising a straight portion which extends outwardly from the end of the respective lower lateral side at said outer open side in a direction substantially perpendicular to said central symmetry plane, and wherein the at least a space between the inserted ending of the curved section (422, 442) and the groove opens on the outside of the rail and is a continuous space formed between said inner bottom side of the grooves and said end side of the curved section (422, 442) and between said lower lateral side of the grooves and said second side of the curved section (422, 442), the space between said lower lateral side of the grooves and said second side of the curved section (422, 442) widening continuously when proceeding from the inner bottom side to the outer open side. - a main body made of high conductivity aluminum alloy, including an upper head portion, a stem portion and a lower base portion, - a facing cap made of stainless steel, on which a conductive shoe is adapted to slide, said facing cap comprising a central portion adapted to lay against a top surface of the upper head portion and two lateral portions (42, 44) arranged against lateral sides (242, 244) of the upper head portion and welded to the central portion so that the facing cap is secured to the main body, and wherein the grooves have an upper lateral side laying against said first side of the curved section (422, 442), a second lower lateral side, an inner bottom side connecting said upper and lower lateral sides, and an outer open side which is opposite to the inner bottom side and is oriented towards a lower side of the main body and away from said central plane of the main body, characterized in that the longitudinal grooves are broader than the curved sections (422, 442) of the lateral portions (42, 44) and each groove is defined to set at least a space between the inserted ending of the curved section (422, 442) and the groove, wherein said outer open side is wider than said inner bottom side, the grooves further comprising a straight portion which extends outwardly from the end of the respective lower lateral side at said outer open side in a direction substantially perpendicular to said central symmetry plane, and wherein the at least a space between the inserted ending of the curved section (422, 442) and the groove opens on the outside of the rail and is a continuous space formed between said inner bottom side of the grooves and said end side of the curved section (422, 442) and between said lower lateral side of the grooves and said second side of the curved section (422, 442), the space between said lower lateral side of the grooves and said second side of the curved section (422, 442) widening continuously when proceeding from the inner bottom side to the outer open side.