A blondin cableway installation, comprises a pair of carrying cables extending between the two ends of the installation; a carriage provided with a lifting tackle and supported movably on the carrying cables; a lifting cable for operating the lifting tackle, extending between the two ends of the installation; an outward haulage cable for conveying the carriage along the pair of carrying cables, said outward haulage cable being connected via tackle to the carriage so as to have a pair of outward haulage sections which extend between the carriage and each end of the installation; and a plurality of cradles arranged along the pair of carrying cables and suspended from them in a stationary manner and designed to support the lifting cable and outward haulage cable, each of the cradles comprising, on each side, a pair of support rollers able to receive by means of gravity, alternately, the outward haulage cable or the lifting cable, and a corresponding pair of retaining rollers able to bias the lifting cable and haulage cable against the support rollers, the retaining rollers being supported by a pendulum member hinged with the cradle; wherein the carriage has, formed in it, a longitudinal passage which has a cross-section such as to allow it to be passed through by one of the cradles during the movement of the carriage; and wherein the carriage is provided, on each side of the passage, with a cam member able to raise the retaining rollers upon entry of the passage by the cradle, so as to allow disengagement of the lifting cable and outward haulage cable from the support rollers when the carriage is passed through by the cradle, the cam member acting on a respective tappet member integral with the pendulum member.