In order to evaluate fuel consumption and tailpipe emission of a vehicle, standard driving cycles are used to prescribe vehicle driving condition such as speed, gear shift, fluid temperature and so on. New european driving cycle (NEDC) has prevailed as the only driving cycle for emission and fuel consumption while Federal Test Procedure 75(FTP-75) mode is used in the United States. In South Korea, NEDC is applied for emission certification and FTP-75 mode is used for fuel consumption of a vehicle powered by diesel engine. Because these driving cycles are mixed of static phase (cruising and idle) and transient phase (acceleration and deceleration), they need to be transformed to static engine operation condition so that optimization is possible using engine dynamometer for each representative engine operation condition. This study set up two models to convert vehicle driving conditions to engine operation condition based on work which the engine should produce to follow the driving cycle and based on representative vehicle speed of NEDC. Accuracy of each model was compared with actual vehicle test result on a chassis dynamometer and the characteristics of each model were analyzed.