Heavy-duty vehicles constitute a significant contributor to road CO₂ emissions, despite accounting for only a low share of the vehicle fleet. CO₂ Emissions certification and monitoring are performed using vehicle simulation software designed for the purpose (VECTO). The European Union currently regulates rigid truck and tractor-trailer CO₂ emissions and subsequently will proceed to buses and other heavy-duty vehicle categories. The current study investigated the use of VECTO on a city bus by modeling the on-road operating conditions of a vehicle in an urban route in Istanbul. The simulation results for constant auxiliary load showed a difference with the on-road measurements in the range of −1.6 to 3.2%, depending on the direction of the route. The difference was attributed to the influence of the total elevation change, and the use of auxiliaries. The latter comprise a significant part of energy consumption in buses, and for this reason, VECTO includes a dedicated bus auxiliary module. The use of the module was also explored, and it was found to improve the results in some cases. The findings highlight the need to assess the operation of auxiliary components in city buses accurately, and to consider the provision of more precise, auxiliary-component specific, information when running actual real-world CO₂ simulations of these vehicles.

Public transportation fuel consumption modeling shows a great importance because of economic and environmental aspects. Considering to the metropolises with millions of inhabitants with circulating thousands of buses that uses intercity lines, its importance is becoming vital in planning both operation of transportation company and city mobility planning. In this context a detailed fuel consumption modelling approach for public transportation buses was used for vehicle fuel consumption assessment during operation. The methodology was developed with IPG TruckMaker + AVL Cruise co-simulation environment following instantaneous speed, load and 3D road data primarily besides model parameters. The model was validated at one of the most important public transportation axle of the world, Istanbul Metrobus System, at two direction which carries over ~1 Million passenger daily in 24 hours operation with petrol engine buses. The comparison simulation/measurements showed that the proposed fuel consumption model is accurate and can predict fuel consumption behavior for public transit buses in a reliable band. In addition, this methodology can be used to investigate various power train and operating scenarios near future for more efficient public transportation with high reliability.