General regulations These technical requirements apply to passenger coaches being built and those that are being modernised by fitting a specific type of bogie. Passenger coaches which have bogies with dual gauge wheelsets are designed to run on the services between railways with gauges of 1 435 mm and 1 520 mm without a change of bogie and must meet the requirements of the UIC/OSJD Leaflets. Approval of passenger coaches which have bogies with dual gauge wheelsets is regulated by bilateral or multilateral agreements between the railways.