The ballot measure of greatest statewide significance this year will not be voted on statewide. Within the tightly drawn boundaries capturing large portions of King, Snohomish and Pierce Counties, voters will be deciding the fate of Washington transportation policies, perhaps for decades. Their vote on the Roads and Transit package — Proposition 1 — has unavoidable consequences for residents throughout the state.

If the measure passes, we’ll see immediate and long-term progress in addressing the state’s major metropolitan congestion problems and a vindication of regionalism in transportation planning and finance. If it’s defeated, state lawmakers will find themselves unhappily confronting Puget Sound area transportation challenges for which there are no simple legislative fixes.

Five years ago, the Legislature authorized the regional transportation improvement district (RTID) for the three urban counties in the Puget Sound area. The creation of the RTID represented a major break in the way state government handled transportation funding. Traditionally, the state gas tax paid for transportation projects of statewide significance. Every several years, legislators would hike the gas tax to keep pace with inflation and spread the money around, tending to interests on both sides of the Cascades.

From 1991 to 2003, however, the gas tax stayed flat and highway construction fell behind. At the same time, population growth and congestion in the Central Puget Sound corridor increased dramatically.

Lawmakers ultimately responded in two ways. They passed a nickel gas tax hike in 2003 and a 9.5-cent increase in 2005. (The latter received voter approval after an initiative was filed.)

But even as they got serious about the construction backlog, lawmakers recognized that they’d never catch up without substantial additional contributions from the region requiring most of the money. So the RTID was born and a package of local funding options created.

From the beginning, lawmakers linked RTID with Sound Transit (the regional agency responsible for commuter trains, light rail and other transit alternatives). In 2006, the Legislature gave local authorities more options and required a joint Sound Transit and RTID proposal for 2007.

The result: a $17.8 billion package that would also go a long way to improving mobility in a region that is the hub of much of the state’s economy. The state auditor’s recent performance audit looked at various congestion projections over the next 20 years. Without the roads and transit package, the auditors conclude, “delay … would be far more than double the current level of congestion.”

Of the $17.8 billion, $10.8 billion goes to transit, with the $7 billion balance dedicated to major highway projects. With the state gas tax tied to roads, lawmakers always anticipated that the regional solution would emphasize transit. Crafting the plan required compromise, with each trade-off to gain support giving someone else something to dislike. While there’s the expected opposition from the purists on both ends of the transportation spectrum – the anti-roads and anti-transit parties – the plan has attracted widespread business and environmental support.

It has also divided frequent allies. Former Gov. Dan Evans, who was green before green was cool, backs it, as does Gov. Chris Gregoire, and the bulk of the regional political, labor and business establishment. But King County Executive Ron Sims, a former Sound Transit board chairman, stunned many with his dramatic denunciation of the package.

It doesn’t do enough to combat global warming, Sims wrote in a Seattle Times op-ed that elevated temperatures in many boardrooms and offices in the community. Likewise, by opposing the measure, the Sierra Club splits with prominent green groups like Washington Conservation Voters and the Washington Environmental Council.

Right now, the vote is too close to call. Tax hikes are never popular, and this one boosts the sales tax six cents on a $10 item and bumps the car tabs tax by eight-tenths of a percent ($80 a year for a car worth $10,000). But it’s an investment the region should make.

Our large and diverse state cannot prosper without successful regional transportation systems, planned and financed by local taxpayers and elected officials. November’s roads and transit vote is the biggest test to date of this regional approach. We all have a stake in seeing it work — even those of us who can’t vote on it.