Though the city of Burien calls its proposed $25 car-tab fee for walkways and bike lanes a two-year plan, this fall's Proposition 1 doesn't actually mention a time limit.

"It's not going to run two years -- it runs until it's paid for," opponent Chestine Edgar said.

This argument could arise in other cities and counties, perhaps King County Metro Transit, that consider future "transportation benefit districts."

Sound Transit faced a similar issue, with greater consequences, when its light-rail costs doubled in the late 1990s. Opponents sued to force a revote, but state courts ruled that Sound Transit has the right to take as many years and spend as much money as needed, to deliver its projects.

Burien proposes to add or rebuild sidewalks, and paint bike lanes, on Southwest 136th Street from Ambaum Boulevard Southwest to Des Moines Memorial Drive South; and build a trail along Eighth Avenue South near Cedarhurst Elementary School.

State law calls for the taxes to be retired 30 days after projects are finished, or when their debt is paid off. If there are cost overruns of more than 20 percent, a public hearing is required.

To stay on schedule, Burien would need to closely manage construction contracts. At this point, public works staffers expect that the walkways would be built entirely within publicly owned right-of-way, said Jenn Ramirez Robson, a city management analyst. That ought to reduce the risk of delays by lawsuits.

City projections call for the tax to raise $1.2 million over two years, and the projects to cost $850,000 to $1,050,000 total.

Burien voters are the first in Washington state to consider a car-tab fee to fund bicycle and pedestrian routes.

If citizens support the plan, they might be asked to renew the fee two years from now, to fund walkways in other neighborhoods, according to Mayor John McGilton.