Developing a system dynamics approach for CNG vehicles for low-carbon urban transport: a case study[Towards green cities in developing countries: Egyptian new cities as a case study]

Today both the economic growth and expansion of urbanization have increased community access to private cars. Thus, the urban transportation has become a critical part of energy consumption and greenhouse gas emissions. The excessive dependence of urban transportation on high-emission fuels is the main obstacle to develop a low-carbon transport. Meanwhile, natural gas is a bridge fuel to develop a low-emission transport. To the best of our knowledge, there has been little attention towards the association between the development of natural gas-fueled vehicles and the CO2 emission. Therefore, the problem we studied is the role of compressed natural gas (CNG) vehicles in replacing high-emission fuels. In this study, we aimed to study this association by selecting the system dynamics approach due to the complexities of the social-economic system of transportation. In this modeling, different subsystems of the transport fleet were employed including CNG vehicles and urban transportation subsystems. Iran has used CNG as an alternative fuel in the transportation sector, making it one of the three leading countries in the use of natural gas in the urban transportation system. Our case study is focused on Tehran, which is the capital and the largest city of Iran.In this paper, we considered several scenarios to replace the gasoline fuel in the private car sector and taxis and diesel fuel in the bus fleet with natural CNG fuel. The results show that the replacement of CNG fuel with high-emission fuels can have a significant effect on reducing CO2 emissions. In the synthetic scenario, CO2 emission will be decreased by 11.42% in 2030, as compared to the business as usual (BAU) scenario in this year. According to Iran’s commitment to the Paris Agreement, the emission of CO2 in Iran should normally be reduced by 4% in 2030, as compared to its amount in the BAU scenario. Therefore, Iran can easily fulfill its obligations in the urban transport sector only by replacing gasoline and diesel fuel with CNG.