Trends of initial investment for ventilation and air conditioning in underground railway projects based on sample statistics

 This paper analyses the initial investment of underground railway ventilation and air conditioning of several sample projects. Based on the gray box theory, introducing the “price index for investment in fixed assets” linked to the national economy, the inherent law of the trends of initial investment for ventilation and air conditioning in the underground railway is revealed and verified. The “recommended initial investment for HVAC in underground railway” can be obtained by fitting the “price index for investment in fixed assets” as an indirect independent variable through linear regression, which can provide a more accurate quantitative description of variations and trends for initial investment of ventilation and air conditioning in underground railways under different vehicle groups and climatic zones, and can also make horizontal comparison and evaluation of the investment level of underground railway ventilation and air conditioning in different regions or cities.