In a win for the Seattle Monorail Project, a judge yesterday rejected claims that the agency's car-tab tax is arbitrary and unconstitutional.

Basically, the tax is legal because voters approved it in 2002, according to Judge William Downing of King County Superior Court. He issued a summary judgment, without the jury trial agency opponents requested.

The plaintiffs argued that the monorail's motor-vehicle excise tax is arbitrary because the tax bills are based on a state table that often values vehicles higher than market or "Kelley Blue Book" value.

But Downing said voters approved a tax calculation based on the state valuation system "... rather than upon the expectation of a curbside appraisal of each individual Ford or Ferrari with its added dings and dents, woofers and tweeters," he wrote.

The lawsuit was filed by eight Seattle vehicle owners. Their legal team includes Henry Aronson, who led the anti-monorail campaign in 2002.

The state Department of Licensing, which collects money on behalf of the monorail agency, has said a value-based system would require costly inspections.

But in a legal brief for plaintiffs, Jane Liu, a vice president of Edmunds.com, said her company is capable of supplying true market values that include variations in mileage, equipment, and regional variations.

And the manufacturer's suggested retail price, the basis for the tax table, is 8 percent higher than what car buyers really pay, Liu said.

Monorail opponents also argued that the tax is unconstitutional because only two of the nine monorail-board members are elected by the public, and seven are appointed.

Downing said the structure was approved by voters. "The court cannot find the slogan 'taxation without representation' to fit these circumstances," he said.

The monorail plan passed with a 50.2 percent "yes" vote in 2002. It was upheld in 2004 when 63.5 percent of city voters turned back an initiative that would have gutted the project.

The tax, averaging $130 a year, applies to cars at least 1 year old that are owned by residents of Seattle.

Monorail Finance Director Jonathan Buchter has said the case creates uncertainty in financial markets, impairing the effort to sell $1.7 billion in bonds for the proposed Green Line, a 14-mile route from Ballard to West Seattle.

"We think this certainly helps," Buchter said of the strongly worded decision.

Bill Severson, an attorney for the car owners, said he'll recommend an appeal, directly to the state Supreme Court.

"He [Downing] certainly parroted back, in shortened form, the monorail's arguments," Severson said. Severson said he hopes justices will take a closer look at whether a non-elected board can impose taxes. Monorail activist Peter Sherwin said he hopes the case is resolved quickly.

"We've got a project that may or may not go. We're on the cusp of finding out. So let's have some certainty," he said.

Meanwhile, negotiations continued yesterday between monorail leaders and Cascadia Monorail, which is proposing to build the line.

Tomorrow night, monorail-board members will consider whether to set a deadline.

Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com.