The Orange County Register » Much like the federal gas tax, the California state gas tax of 18-cents per mile has not been increased in over 20 years. California is among several states studying the revenue producing potential of a vehicle miles traveled fee or tax and possible methods of implementation. A mileage-based fee is already being used in some parts of Europe and Asia. In Singapore the mileage-based fee has helped ease traffic congestion, while in Germany high-polluting trucks are charged a higher fee which has helped reduce air pollution and traffic congestion.