The state of California commissioned a report by CalTrans to look into the viability of a mileage-based tax on all vehicles to eventually replace the tax on fossil fuels.

Earlier this year, the state passed its first fuel tax increase since 1994 to pay for the state's infrastructure costs. The measure added 12 cents in tax per gallon to gasoline and 20 cents on a gallon of diesel fuel.

Despite the increased revenue expected from updating the fuel tax, the state is already looking at a tax that is based on mileage instead of gallons, in order to counteract the drop in fuel taxes from increasingly efficient conventional and alternative-powered vehicles. While the new increase should be more than capable of funding the state’s infrastructure costs for now, a recently released report from CalTrans shows that a gas tax will not be able to keep up in the future.

“When initially instituted, the gas tax methodology was an equitable revenue system, generally due to vehicles having comparable fuel consumption rates,” the report states. “However, as more fuel-efficient vehicles are entering the California fleet, the gas tax limitations have become more apparent.”

The study looked at data over a nine-month period from more than 5,000 vehicles ranging from passenger through heavy-duty commercial vehicles. Using a variety of manual and automated methods for tracking miles, the participants simulated the tax at a 1.8-cent-per-mile rate. The rate was based on a five-year average of the gas tax and represented a revenue-neutral option.

Overall, the report determined that a per-mile tax was a viable alternative to a gas tax or other methods. However, it acknowledged that there were issues that needed to be worked out, such as reliable methods for tracking and exchanging data and then using that information for billing. One of the points in favor of the current per-gallon fuel tax is that it can be assessed and charged at the pump, requiring no information from the vehicle.

Some methods being studied would require installing a device that communicates with a vehicle at pumps and battery chargers to confirm mileage numbers and assess a charge. For commercial vehilces, on-board devices like electronic logging devices that plug into the diagnostic port could be used for the purpose.

Joe Rajkovacz, the director of governmental affairs and communications for the Western States Trucking Association, told HDT that he participated in the pilot program so he would be able to comment intelligently to members about it. He characterized participation in the pilot as simple enough, and said he used an ECM style plug-in to allow vehicle tracking.

He was still skeptical about whether the mileage tax would have resulted in more revenue to the state than a traditional collection method. However, Rajkovacz’s take was that a vehicle mileage tax was likely the only way to fairly tax fuel-efficient or alternative-fueled vehicles. 

This was a sentiment shared by 73% of the participants in the pilot program, according to the report.

“Since this state is pushing for zero/near-zero emissions mandates (elimination of fossil fuels), the reality is the fuel tax isn’t going to work to collect highway use fees from those operating alt[ernative fuels],” Rajkovacz told HDT. “Many who operate these kinds of vehicles think they are something special, and ironically kick back at the notion of paying their fair share to use highways, thinking the fact they drive zero-emissions vehicles is so noble they shouldn’t have to pay at the same level all other motorist do.”