The regional Metro government in the Portland area is pushing forward with plans for a 2020 tax measure to support transportation upgrades, from an extension of light rail to bridge improvements to Interstate 5 widening.

But just exactly how the tax will work and what projects will receive funding remains unknown.

A Metro-commissioned poll released in early 2019 showed that potential voters are strongly willing to support a 2020 ballot measure that increases personal and other taxes to fund the improvements, especially if the plan includes the widening of interstates and roads and repairs to Willamette River bridges.

Voters, according to the poll conducted by FM3 Research, also support light rail improvements, but want those to fall in priority behind the road widening.

Metro, which covers a tri-county region that includes Multnomah, Washington and Clackamas counties, said the poll showed support for improvements to the overall transportation system and gives the governmental agency confidence to push forward on planning for a 2020 measure, including deciding how to structure potential taxes and determining which projects get priority.

An earlier 25-year transportation plan, laid out by Metro council chair Lynn Peterson, equals $47 billion. Metro has previously suggested a 2020 package could range as high as $20 billion.

A task force that includes elected leaders and the community will work to whittle down the project list. Key items already discussed for potential inclusion include a nearly $3-billion TriMet light rail extension through southwest Portland to Bridgeport Village, replacements of both the Ross Island and Burnside bridges, expansion of Oregon 217 and Interstate 5 at bottleneck points and even potentially a replacement of the Steel Bridge with a $5-billion transit tunnel.

While the support gave Metro a positive starting point with 60 percent of those polled “very willing” to pay $100 per year for the upgrades and 55 percent at least somewhat willing to go as high as $300 per year, there will still be differences across the voter demographics that need to get sorted out. Those in Clackamas County, for example, weren’t as likely to support the plan and with so many Portland-area commuters still driving solo, the plan will need to include upgrades that ease commute times for every type of traveler. Figuring out the final recipe for a potential plan will be the next challenge for Metro and transportation improvements.

Follow Tim Newcomb on Twitter at @tdnewcomb