Starting this fall, the state of Washington will test a "pay by mile" pilot program as an alternative to the gas tax. On Tuesday, they shared more on how the program would work.

“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, executive director of the commission.

The one-year study, which will involve 2,000 volunteers, would 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.

Right now, people in Washington pay a tax of 49.4 cents per gallon of gas. 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.

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.

“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 Tuesday’s meeting.

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 state plans to seek out and select 2,000 drivers in the coming months to participate in the pilot program. These drivers would be in both metropolitan and rural areas. The state created a website - - where drivers can sign up for the pilot program.

Related links:

Washington Road Usage Charge Pilot Project

Washington Road Usage Charge - Frequently Asked Questions