Vehicle standards are internationally harmonised to a large degree — although the USA is a major non-adherent — and based on the United Nations Economic Commission for Europe (UNECE) standards. They are fundamentally performance-based, although they also include significant prescriptive elements in some areas. For example, the door latch regulations are based on a performance standard, requiring that latches be able to withstand a specified pressure but also include a prescriptive requirement that doors must hinge at the front, unless the front door is designed to close over a rear hinged back door.