Transit vehicles, which use Delhi roads but have no business in Delhi, pose a serious management challenge. Transit vehicles pose a serious problem, as there is a wide divergence between the emission regulations enforced in Delhi and outside the city. While Delhi adheres to Euro II standards, cities neighbouring Delhi mostly adhere to Euro I standards. Thus the transit vehicle, which uses Delhi, contributes considerably to the pollution load in the city. These transit trucks thus negate whatever gains Delhi is making as a result of cleaner fuels.