An aerial transport installation with back-and-forth movement includes two carrying-hauling ropes extending in two individual closed loops between two end terminals separated from one another by an intermediate station which is provided with a double pulley. The latter is provided with two grooves having different groove root diameters, such that the ratio of the diameters is equal to the ratio respectively of the axial distance between the first bull-wheel and the double pulley and of the axial distance between the second bull-wheel and the double pulley. The speeds of the vehicles are also different in the two loops.