Here's something to consider the next time you're stuck in traffic in downtown Portland: If city planners succeed, that congestion won't improve.

In fact, it might even get worse.

As they work on a wide-ranging

a blueprint to ensure that downtown Portland's next 20 years are as successful as its past 40, planners and citizen volunteers have come up with a strange, fascinating, seemingly counterintuitive equation. For Portland to remain the healthy cultural and financial heart of the region, they say, the number of trips made downtown each day must double. The amount of greenhouse gas emitted must remain the same. And the number of

in the central city -- the average number of miles each of us put on our odometer on any given day -- must drop by close to 40 percent.

More trips. The same pollution. Fewer miles.

"It's a head-scratcher when you first think about," said Andre Baugh, chairman of the Portland Planning and Sustainability Commission, the volunteer group that helps craft city development policy.

The series

Portland city leaders are in the process of coming up with a plan to guide development in the central city through 2035. Planners and a committee of citizens and stakeholders will present guiding principles to the Portland City Council on Oct. 24.

Part 1:

Part 2:

Keeping downtown Portland vibrant requires rethinking what it means to live and work in the "central city."

Part 3:

Live chat:

for a chat about this series.

But the projections tie into what the experts say central Portland must become to remain the region's economic heart: A city that feels more like ... a city.

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Back in

, when city leaders and citizen activists came up with the first major plan for downtown development, the idea of living in the central city was unfathomable. Today, it's inevitable.

Demographers predict that the Portland-Vancouver region will pick up another 402,400 households -- not just individuals -- by 2035. Because of the urban growth boundary, there are only so many places for them to go.

Central cities are hot again. Younger Americans don't mind living in smaller spaces if it means more access to cultural attractions and great restaurants, and fewer trips to the gas station. Economists say that even in regions that stretch out over hundreds of miles and contain multiple population centers, the urban core is the great incubator of creative thought, and, in turn, the next generation of economic success.

When planners looked closely at the Pearl District a few years ago, they were stunned at how many young creative types were sticking around even after their children reached school age. That push back to the core is happening nationally -- a larger percentage of Americans lived in urban areas in 2010 than 2000, according to the U.S. Census Bureau.

"Cradle to grave is the new goal," said Troy Doss, a senior planner who is helping craft the new 20-year plan for downtown. "People want to settle in the city when they're young and stay the rest of their lives. Our job is to make sure this is a place where you can do that."

Planners expect a third of the 132,000 new households coming to Portland in the next 20 years to land in the center city. That sounds big. But zoning codes and planning guidelines call for

than exists right now. According to the 2010 U.S. Census, Beaverton had more people per square mile (4,795) and housing units (2,109) than Portland (4,375 people, 1,989 places to live).

Density in the Portland Region Area People per square mile Housing units per square mile Region 333 138 Beaverton 4795 2109 Portland 4375 1989 Hillsboro 3833 1484 Vancouver 3482 1506



Source: U.S. Census Bureau

The northern part of the Pearl District isn't built out. South Waterfront has barely begun growing. And Goose Hollow and the Lloyd District, two neighborhoods that nobody would have considered downtown even a decade ago, are now part of the central city in the eyes of the people who decide how Portland develops.

Forty years ago, the newly opened Lloyd Center was seen as the great threat to downtown retail. Now planners talk about the Lloyd District soon feeling like Brooklyn or parts of Washington, D.C.; the neighborhood has all the transportation infrastructure it needs, including the newly opened streetcar line and light rail, and the market is finally catching up. Developer Scott Langley is building a 750-unit mixed-use complex that planners say will be the rule rather than an outlier.

If the dominos of development fall the way they're supposed to, a boom in the Lloyd District will trigger similar changes in the Central Eastside just to the south. And 20 years from now, new development will have filled in the gaps in a large downtown loop that stretches across the river.

Portlanders have a complicated relationship with the concept of greater density, however. Consider the ongoing controversy about new apartment complexes going into inner-city neighborhoods with fewer parking spaces. City leaders have pushed such projects for more than a decade as a way to reduce air pollution and increase mass transit ridership. Yet now that developers -- and the bankers who decide how much they can borrow -- have caught up, neighbors are objecting.

"We love density until it's right next door," said Doss, the city planner. "We love it in theory, but not necessarily in practice."

Portlanders are used to a certain quality of life -- easy, pleasant, stress-free compared to larger, more sprawling U.S. cities. Putting more people in the same space poses both practical and psychological challenges to that sense of Portland as Pleasantville.

"The problem with that word, 'density,' is that people hear it and go, 'Click.' They just shut down. They don't want to have the conversation," said Mike Houck, a planning commission member and a conservationist who runs the

. "How about instead we talk instead about making the most effective use of available land?"

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Regardless of what you call the changes to come, the Portland of 20 years from now will have more people competing for a share of roads and sidewalks that aren't expected to expand much more.

Transportation engineers say that 16 percent of the city's major downtown entry points are congested today. By 2035, they expect that to hit 26 percent.

Those numbers might seem scary to people stuck in traffic on Naito Parkway or U.S. 26. To the planners and civic activists working on the 20-year plan, however, they're more a reality to be addressed than a crisis to be solved.

That's where that seemingly magical equation -- more trips,

, the same pollution -- becomes important. Portland needs more people and jobs downtown. The key to the traffic future is to make sure those people are coming to stay, not cutting through to avoid backups on Interstate 5.

Vehicle miles traveled per capita, now and projected Area 2005 2035 Central city 12.8 10.3 Portland 15.9 14.3 Region 16.6 15.7

During the past 40 years, taxpayers have spent billions of dollars on infrastructure designed to move people from place to place faster and in greater numbers. Beyond more bike lanes, completion of the streetcar loop and a solution to the problem of Interstate 5, the age of massive physical changes downtown is ending and the role of government is changing. In the next 20 years efforts downtown will be away from construction and toward nudging the private sector to make sure all those new central city residents and workers have enough parks, schools, markets and family-friendly housing.

If everything goes right, the expanded central city will be thick with the same kind of walkable, self-sufficient neighborhoods that ring it -- and with people going about their daily lives in the shadow of what pass for skyscrapers here.

"It becomes a place where you don't have to get in a car every day," Baugh said.

"We're talking about going from a place where you have housing to a place that is filled with actual neighborhoods," said Joe Zehnder, the city's senior planner.

The bad news: Traffic will still be a sticky issue, probably stickier than now.

The good: There are far worse problems for a city to have.

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