Due to the variability of real traffic conditions for vehicle testing, real-world vehicle performance estimation using simulation method become vital. Especially for heavy duty vehicles (e.g. 40 t trucks), which are used for international freight transport, real-world tests are difficult, complex and expensive. Vehicle simulations use mathematical methods or commercial software, which take given driving cycles as inputs. However, the road situations in real driving are different from the driving cycles, whose speed profiles are obtained under specific conditions. In this paper, a real-world vehicle performance estimation method using simulation was proposed, also it took traffic and real road situations into consideration, which made it possible to investigate the performance of vehicles operating on any roads and traffic conditions. The proposed approach is applicable to all kind of road vehicles, e.g. trucks, buses, etc. In the method, the real-road network includes road elevation. The traffic conditions and vehicles parameters were the inputs for traffic simulation. Based on the outputs (speed profiles and elevations) of target vehicles in the traffic simulation, then the real-world performance of the vehicle was achieved by vehicle simulation under the given traffic conditions. The fuel consumption of the vehicle calculated using this method was 34.00 L/100 km under free traffic flow conditions over highway route.