OLYMPIA, Wash. - Would you prefer to be charged a tax per mile you drive, or per gallon of gas you buy?

Starting in September through the end of the year, the state of Washington will begin testing a "pay-by-mile" pilot program as an alternative to the gas tax.

The state is currently recruiting 2,000 volunteers in both rural and urban areas to participate in the 12-month Washington Road Usage Charge Project. The study would help officials figure out ways to charge car owners a tax based on how many miles they've driven within the state, rather than how much gas was pumped. Volunteers for the pilot program will be expected to commit about 10 minutes per month reporting their mileage and providing feedback, beginning in early 2018.

“The legislature and the commission have been looking at this since 2012, and we think it’s a viable approach, but now it’s time to test it,” said Reema Griffith, Transportation Commission executive director.

Right now, people in Washington pay the second highest gas tax in the nation at 49.4 cents per gallon. That tax pays to fix roads, bridges, and ferries. But with the rise of electric and hybrid vehicles, as cars get more efficient and pay less gas, that means less revenue for the state.

“Based on the test, we may find out that it is a good idea or maybe it isn’t, and if it’s not, we go back to square one as we prepare for that ultimate future we see coming,” said Griffith.

"We know we're going to hit the tipping point at some point," said Josh Brown, a former Kitsap County commissioner who heads the Puget Sound Regional Council, which conducted a similar study. "For 100 years, the gas tax has been a very good funding mechanism for a user fee for vehicle travel. In a couple decades, when we're not filling up our cars anymore and half or more of us are driving electric vehicles, how do we support our federal and state investments?"

"It's simply a scientific test to see how it works from a technical, mechanical and operations aspect, but more importantly it's an opportunity for residents across the state to experience it and give feedback to the state on what worked and what didn't work and what they liked and didn't like," said Griffith.

Currently, the average car gets about 20 miles per gallon. In 20 years, that's expected to be 35 miles per gallon - a drop in gas tax revenue by 50 percent.

It will take about eight years before drivers see a possible switch to the pay by mile system, which some drivers felt was too long. Officials say that the pay-per-mile tax would gradually replace the state's pay-per-gallon tax.

“I know the ultimate goal is where is our money going to come from, but I’d like to know that the money that they have now is being spent properly,” said Lynn Cooper, who attended a meeting in May of this year.

How would the state track road use in the pilot program? The state says there are four options volunteers can choose from:

A mileage permit, where a driver chooses how many miles to purchase.

Odometer readings: A per-mile charge would be based on the vehicle odometer.

Automated mileage meter: A device installed in the car would report miles driven. Drivers would choose GPS or not.

Smart Phone: A downloadable app would use the driver's phone to record and/or report miles driven.

The Kitsap Sun contributed to this report.

Related links:

Washington Road Usage Charge Pilot Project

Washington Road Usage Charge - Frequently Asked Questions