A brake control apparatus for railway cars having sprung and unsprung portions is interposed between a brake pressure supply line and a brake cylinder line. A first chamber is connected to the brake pressure supply line and a second chamber is connected to the brake cylinder line. The chambers are abutted by surfaces having different cross-sectional areas of a diaphragm which is biased. A first valve responsive to positioning of the diaphragm, and a second valve responsive to positioning of a strut in a strut cylinder, effect first and second predetermined relationships between pressure drop in the brake pressure supply line and pressure drop in the brake cylinder line. The strut cylinder, mounted between the sprung and unsprung portions of the railway car, may be adapted to sense partially loaded as well as fully loaded or unloaded conditions.