Abstract: A vehicle suspension gas supply system comprises valve means having a central chamber to which pressurised gas may be admitted and from which pressurised gas may be exhausted, gas communication paths for extending from said central chamber each to communicate with a respective gas suspension unit, and interposed in each gas communication path a valve unit operable to lie either in a closed condition in which an associated gas spring is isolated from the central chamber or to lie in an open position in which the gas spring communicates with said central chamber, a compressor for supply of pressurised gas, a gas dryer interposed between said compressor and central chamber, a remotely operable supply valve operable to allow pressurised gas to be admitted to said central chamber, and a remotely operable exhaust control valve operable to control a pair of slave valves thereby to cause pressurised gas to be exhausted from the central chamber via said dryer.