A new tax based on how much people drive could be among the transportation funding ideas lawmakers consider in 2017, according to a member of the task force exploring the idea.

The Oregon Department of Transportation launched a pilot project last July to test the pay-by-the-mile tax. Vicki Berger, a former Republican representative from Salem and member of the task force, said the state needs new revenue to supplement or replace the gas tax because drivers are paying less as cars become more fuel-efficient.

"Everybody who's ever looked at this comes to, 'Well why not pay per mile instead of on the fuel?'" Berger said, before noting the rise of cars that run solely on electricity. "The famous Tesla pays no taxes to drive on your roads, and that's not going to be viable."

Berger said the task force plans to release recommendations in September for legislation to charge the mileage tax on certain vehicles -- perhaps only on specific types of vehicles or all new cars sold after a future date.

Oregon was the first state to test the concept, and California and Washington are now preparing to launch their own pilot programs. Yet the pilot program designed to test the program has fallen short of its enrollment goal, despite the transportation department spending at least $6.4 million on the project according to a state application for federal funds.

As the one-year anniversary approaches, the state has enrolled only 891 drivers, a fraction of the 5,000 volunteers state officials hoped to sign up for the program. Michelle Godfrey, an education and outreach coordinator for the Oregon Department of Transportation, said she did not know how many participants the state needed to properly vet the system.

The number of vehicles in the pilot is slightly higher, at 1,018, but that number got a boost when the transportation department signed up the fleets of four of its contractors. They account for 50 vehicles in the program, and all four contractors were signed up after solicitations from transportation department staff, Godfrey wrote in an email. The contractors do work including paving and highway construction.

Transportation staff promoted the program at events attended by contractors, after a public relations firm hired by the state failed to sign up any independent vehicle fleets, Shelley Snow, a department spokeswoman, wrote in an email.

The state has spent $514,735 since April 2014 for the public relations firm PRR to promote the pilot project and sign up volunteers. The state's contract with the firm allows it to spend up to $650,000.

The four contractors who signed up are Knife River, K&E Excavating, Lakeside Industries and Bayview Transit Mix. Knife River had $13 million in active contracts with the transportation department in fiscal year 2015, and K&E Excavating had $39.1 million, according to a state contracting database. It was unclear when Lakeside Industries and Bayview Transit Mix might have had state transportation contracts.

Asked about his company's participation, Brian Gray, president of Knife River's northwest region, said there were "absolutely no incentives" to join the program.

"There's no benefit of being part of that," Gray said, "other than participating in an alternative long-term funding mechanism for transportation."

Travis Brouwer, assistant director of the Oregon Department of Transportation, said department staff mentioned the mileage tax pilot project at a regular meeting between the department and industry leaders.

Brower said he did not know why the only vehicle fleets enrolled were transportation department contractors, but said "transportation stakeholders have a stake in having a long-term, sustainable funding source."

Knife River's Gray said the company has an interest in Oregon, other states and the federal government finding more money for transportation.

"Knife River is heavily dependent on transportation funding, and we also realize that the current system is not adequate, ... that people are driving fewer miles, that cars are getting better gas mileage and with the hybrids and electrical cars there's got to be a better system in the future," he said. "The more data we get and work out the bugs, the better."

-- Hillary Borrud

503-294-4034; @hborrud