The Portland Streetcar runs on 16 miles of track, past soaring downtown office towers and through neighborhoods offering postcard-perfect river views.

But it was an unassuming spot near a short curve in the track, where the streetcar line's eastside spur meets the Tilikum Crossing bridge, that Dan Bower recently met a group of touring transportation officials.

"This," the director of Portland Streetcar Inc. said, "is our most important 45 feet of track."

The short section, opened at the same time as Tilikum Crossing in September, completed a full loop of Portland's central city. With it, a decades-old vision for a streetcar line circulating residents and visitors throughout the city's core was finally complete.

But streetcar officials aren't done. Bower's nonprofit, the city and TriMet are now negotiating a new vision, considering additional spurs that would compete with existing TriMet bus routes.

Few other cities have dared put streetcars up against workhorse bus fleets. A commuter route would tie the streetcar more tightly into the city's transportation network, and the experiment would be closely watched by cities across the country that have their own fledgling streetcar lines.

"What's going on here is an evolution from where we started out with streetcars to where we might be headed," said Portland Mayor Charlie Hales.

But it could also shine a spotlight on its shortcomings. Some transit experts say expansions could cost taxpayers a lot of money without improving service for commuters. Worse, an expanded streetcar network could actually hurt the commuting public by cannibalizing the bus system.

"Quite simply, the streetcar must prove that it is making speed and reliability better rather than worse, compared to the bus lines that are there now," said Jarrett Walker, a Portland-based public transportation consultant. "If a streetcar plan fails that test, then it is likely to make travel times and reliability worse while consuming money that could have been spent on making them better. This is going to be controversial."

Economic development origins

The streetcar is confronting an identity crisis that dates to its founding.

The Portland Streetcar made one of its first appearances in city plans in 1988 as a vintage trolley that would connect microbreweries, art galleries and retailers in what would later become the Pearl District.

It was conceived of primarily as a tool for economic development, designed to encourage housing development in downtown Portland and what would become the Pearl District. Backers claim credit for billions of dollars in economic development and property value increases along the route.

At $251 million to build, "It's the single best investment the city has ever made," said Hales, who promoted the streetcars both as the city's transportation commissioner as a private-sector consultant.

The Portland Streetcar is owned by the city, but its day-to-day operations are overseen by Portland Streetcar Inc., an organization with a board of directors made up largely of developers and others involved in real estate.

Despite that focus, at 15,200 passengers a day in April, the streetcar's ridership approaches that of the MAX Yellow Line. Hour-for-hour, it's busier than most bus lines.

Under Bower, a former Portland transportation bureau manager who in 2014 became Portland Streetcar Inc.'s first full-time director, the streetcar has made moves to improve its transit bona fides.

It has closed stops in order to decrease trip times through downtown, and Portland has approached Seattle about buying surplus streetcars to increase frequency.

"We should be doing everything we can to squeeze every last dime of out this existing system," Bower said. "As for growing the system in the future ... the best investment is to leverage it with little spurs out of it."

Dual missions

Along the way, Portland's streetcar has drawn criticism. In 2014, the office of the elected auditor found potential for conflicts of interest in the cozy relationship between Portland Streetcar Inc. and the city, ostensibly its client.

It followed up later that year with a second audit that criticized the city for not holding the streetcar accountable to stated goals. The city, for example, said it wanted the streetcar to be on time 98 percent of the time. Few, if any, transit systems could meet that high standard, and the streetcar couldn't come close. (The goal has since been relaxed to 85 percent by 2020, and the streetcar is currently at 82 percent.)

Yet the city had gone on to approve expansions that added complexity to the system. Meanwhile, the lack of a strategic plan for the streetcar left auditors confused as to how the city might evaluate expansion proposals.

"Is the system here for transit, or is the system here for economic development?" said Drummond Kahn, the city's director of audit services. "Streetcar suggested the system was there for both, but our audit found that it is unclear how the city reconciles any competing goals. Clear, overall goals would help any system decide when to expand and, if they do, which routes to prioritize."

The streetcar has since assembled a strategic plan that includes both transit performance goals and budget goals. It also outlines plans for the next expansion, with the goal of teeing up "at least one" new streetcar route for funding.

Expansion on commuter routes

Options under consideration include spurs that extend north on Martin Luther King Boulevard; east on Sandy Boulevard to the Hollywood neighborhood; east on Broadway Boulevard to Hollywood; or south from the South Waterfront on Macadam Avenue.

Each is a heavy transit corridor, some already served by frequent service bus lines, potentially putting regional transit agency TriMet in an awkward spot.

Though the city owns the streetcar and Portland Streetcar Inc. administers it, the streetcars are driven and maintained by TriMet employees, and the agency pays at least half the operating costs of each existing line. TriMet's contribution increases over time -- provided people are riding it.

"We expect the streetcar to serve a mobility role early and grow from there," said Alan Lehto, TriMet's director of planning and policy. "If we see a plan that doesn't seem to do that, we're going to have some questions."

And, he said, the system shouldn't replace the bus, forcing long-distance passengers to get out and transfer.

"The system has to work together," he said.

A streetcar could be an upgrade for some. Streetcars can carry more people than a bus and offer a smoother ride.

Like buses and unlike MAX, streetcars usually travel in traffic lanes and can get caught up in congestion. But unlike buses, streetcars are unable to go around a stopped vehicle or to temporarily reroute. They also don't offer the operational savings of MAX, which carries four times as many passengers as a bus.

"This is why very few American mixed-traffic streetcars have been built replacing existing bus lines," said Walker, the Portland transportation consultant. "The comparison with the existing bus service usually shows the streetcar is worse at actual travel time and access outcomes, and especially at reliability because of all the situations that will disrupt streetcars but not buses. "

Those issues leave transit experts skeptical a streetcar system would be worth the expense.

"The streetcar is really what planners call a place-making tool, not a transportation tool," said Aaron Golub, an associate professor at Portland State University. "It's not meant to transport a lot of people quickly, which a bus does."

But Bower said that belies the streetcar's growing transit role.

A survey showed some 32 percent of riders took the streetcar to work. Another 17 percent took it to college classes. And Bower said the streetcar deploys its wheelchair ramps more often than TriMet buses, suggesting frequent use by seniors and people with disabilities.

"It's not Carrie Bradshaw going from the Pearl District to the art museum and back," Bower said. "You've got 15,000 people riding this thing. It's really a disservice to all these people to just call it a development tool."

Cities look to Portland

A streetcar takes a practice run along Main Street in Kansas City, Mo., Wednesday, April 27, 2016. The new streetcar started operations in May with officials from Portland in attendance.

Portland's "modern streetcar" has become a model for cities across the country to move people around their downtown core. Brand-new streetcar systems have opened this year in Washington, D.C., and Kansas City, Missouri, and others are under construction in Detroit and Cincinnati, Ohio.

The national movement has been helped along by the Obama administration, which changed the way transportation agencies evaluated transit projects when doling out funding. Now, land-use and economic development can add weight to a project, along with cost effectiveness, rider time savings and reducing congestion.

"That's helped fuel the rush," said Art Guzzetti, the vice president for policy at the American Public Transportation Administration.

A recent analysis by researchers at the Mineta Transportation Institute, however, found that other cities should be cautious in following Portland's lead. Co-author Jeff Brown, who chairs the urban planning department at Florida State University and calls himself a streetcar skeptic, said most cities aren't treating their streetcar systems like legitimate transportation modes.

Portland, he said, has tried to balance transportation needs with economic development goals. But it could, perhaps, take a lesson from its own success.

"What are the implications for riders?" Brown said. "Is all of this going to actually lead to an overall ridership increase, and at what cost? From a transportation perspective, that's what we should be concerned about."

-- Elliot Njus

enjus@oregonian.com

503-294-5034

@enjus

This article has been edited to correct the spelling of Jarrett Walker's name.