GB/T 20969.5-2021 "Special environmental conditions plateau machinery, Part 5: Guidelines for testing of plateau natural environment Engineering machinery" regulates the performance test, type test and setting test of Engineering machinery in plateau natural environment at altitudes of 2000 meters to 5000 meters. This standard applies to Engineering machinery equipped with internal combustion powered machinery to guide its detection and evaluation in plateau environment. The document specifies in detail the test methods and requirements to ensure that Engineering machinery can operate reliably under plateau conditions and meet performance standards. The content involved includes traction testing, driving speed measurement and exhaust pollutant measurement, etc., to ensure the adaptability and Stability of Engineering machinery in special environments.