This code is intended for commercial vehicles over 4500 kg (10 000 lb) with brake systems having typical service pressure ranges 0 to 14.1 mPa (0 to 2050 psi) hydraulic or 0 to 830 kPa (0 to 130 psi) air and is not directly applicable to vehicles with other systems. Air over hydraulic systems are to be tested as air systems.