Seattle Mayor Jenny Durkan and King County Executive Dow Constantine warn Initiative 976, which seeks to cap car tabs at $30, would be “catastrophic” for the region’s transportation plans.

The two led a press conference Tuesday morning, outlining what they say are the impacts and relabeling the campaign as “No on Tim Eyman’s I-976.”

The initiative, led by anti-tax crusader Eyman, comes amidst debate over how vehicle tabs are calculated after the passage of Sound Transit 3 (ST3) in 2016.

The no campaign says passage of the measure will increase congestion and kill state funding for projects on Interstate 405, State Route 520, State Route 167/SR 509, and Interstate 90 near Snoqualmie Pass. They also claim it will cripple funding for light rail expansion and likely dramatically alter the package approved by voters three years ago.

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Durkan said at the press conference that Seattle would lose hundreds of thousands of hours of bus service at a time when the city is growing exponentially.

Eyman argued that those road projects, which are partially paid for through gas taxes, could "easily be refilled" through other state funding.

"With the state having a $3.5 billion net surplus and record revenues, politicians threats, lies, and scare tactics are particularly unbelievable and absurd," Eyman said. "There is more than enough revenue to backfill any affected government program."

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I-976 was certified in January, and voters will decide on the measure in November.

Voters previously approved $30 car tab caps in 1999 and again in 2002. Annual fees were raised after voters approved a $54 billion tax package in 2016 to pay for transportation projects.

If I-976 were approved, Sound Transit estimates it would eliminate $6.95 billion in anticipated revenue through 2041 and limit the amount of funding available through bonds.