Abstract: Recently years many efforts in transportation field have been attempted in order to overcome the global warming and climate change impact such efforts in reducing vehicle emission from the road sector. In this regard, some tools have been developed for calculating the vehicular emission quantity. However, those tools based on homogenous traffic situation in developed countries. Due to the difference of traffic behaviors on a heterogeneous traffic situation will leads to the difference on an exhaust emission from vehicles, it seems important to develop a calculation tool for such traffic situation. Regarding this, this study aimed to develop a calculation tool of vehicular emission quantity for heterogeneous traffic conditions, namely MARNI (Metropolitan Road emission Inventory) 2.2. The tool is developed based on the MARNI Model, an empirical calculation model for vehicle emission quantity based on an urban road condition in Makassar, Indonesia. The MARNI 12.2 is constructed using C# language programming on the Microsoft Windows platform. The tool is applied for the vehicle emission calculation on an arterial road in Makassar City and we compare the results using IVEM software, a calculation tool based on International Vehicle Emission (IVE) Model that developed for developing countries condition. The results provide a significant confidence in the vehicle emission calculation for the heterogeneous traffic situations. However, the MARNI 12.2 still covers passenger car types only, we expect to complete the tool involving motorcycle and heavy vehicle types in the future research activities.