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Sky’s the Limit

An aerial tram in Portland, Oregon carries passengers from downtown to a hilltop campus, reducing commuting time and vehicle miles

By Nancy Hill

Part of the city’s public transportation system, the tram connects Oregon
Health & Science University with the
South Waterfront District

Long before skyward-bound transportation became more than a dim concept in even the most brilliant mind, events were paving the way for Portland, Oregon’s $57-million tram that would facilitate travel between upper and lower campuses of the Oregon Health & Science University’s (OHSU) renowned medical facilities. Known as the Portland Aerial Tram, today it travels a horizontal distance of 3300 feet and a vertical distance of 500 feet in a three-minute ride. It began service in January 2007 and has carried over a million passengers.

Looking back, the year was 1917, and thanks to the influence of Union Pacific Railroad’s Chief Surgeon Dr. Kenneth Mackenzie, the Oregon-Washington Railroad and Navigation Company (OR&N), a subsidiary of Union Pacific, donated a 20-acre tract of land to what was then the University of Oregon Medical School. OR&N intended to route the railroad through the land but determined it was too steep for that. Moreover, there was only one road to the property, and it was slow going. Within several years, the family of Oregon Journal publisher C.S. Jackson donated an additional 88 acres, and between the two generous donations, the future location of what would become the state’s only health and research university was sealed.

Despite the location atop a hill accessible only through a steep road with hairpin turns, demands for OHSU’s services began to increase from the day ground first broke in 1919. Today, the Marquam Hill campus holds 33 major buildings, and while building capacity has been tapped out, services to patients, researchers, and students have never slowed.

In 2001, OHSU purchased property along Portland’s South Waterfront District to accommodate the need for expansion and in 2003 broke ground for its first building offsite from what is fondly called “Pill Hill.” Plans for additional medical and educational facilities quickly followed.

At this point, eyes began to turn skyward to answer a very pressing question: How would doctors, students, and patients travel between lower South Waterfront District to the hilltop facilities? Getting from the lower campus to the upper campus via public roadway requires a nearly two-mile drive along winding roads with numerous intersections, stop signs, and traffic lights. Surely there was a more efficient way to commute between campuses.

To oversee transportation concerns, a consortium of interested parties, including OHSU and the Portland Office of Transportation (PDOT), formed Portland Aerial Transportation, Inc. (PATI), a private non-profit. PATI’s first action was to ask the city of Portland to conduct an independent study to determine how best to address connectivity issues.

Portland Aerial Project Manager Art Pearce greets Johannes Rindal, an official from Oppland, Norway who visited Portland to gather information on the tram, which has attracted worldwide attention

“OHSU had taken transportation into the equation of building on the waterfront by the time the city of Portland got involved,” says PDOT’s Portland Aerial Project Manager Art Pearce. “When OHSU decided to expand, it didn’t have enough space to grow. They needed fast and reliable transportation and knew surface connections wouldn’t be feasible mainly because of all the freeways going through there.” Additionally, the area had historic neighborhoods and a protected parkway.

Several Options Considered
“A tram or gondola rose to the top of the list fast,” Pearce recalls, and based on OHSU’s study, the city also looked at shuttle buses as an option. The shuttle bus was eliminated quickly. “A shuttle would take 10 minutes on the best day,” Pearce says, “and up to 30 minutes on a bad traffic day. This wouldn’t work well for a seamless connection between meetings and appointments.” Moreover, the frequency of the shuttle buses would have a significant impact on neighborhood residents.

Pearce says research indicated that a tram had considerable advantages over a gondola. “Trams can span long distances without ground structures, operating costs are lower than a gondola system, and connections are faster. Trams also have fewer moving parts, which means fewer risks of breakdowns or repairs.” Additionally, gondolas can only hold four to eight people, while trams can hold 78 passengers. In January 2003, PATI identified four firms to participate in a design contest, confirming that Portland would indeed build a tram.

Designing a tram to meet this very specific need would require considerable ingenuity. Additionally, the city wanted a design that would add beauty as well as function to the city’s transit system. But even before aesthetics were discussed, several critical engineering problems had to be addressed.

“Trams are normally anchored onto hills or mountains,” states Mike Commissaris, who serves as the general manager of tram operations, which has been contracted to Doppelmayr CTEC. “In this case, that wasn’t possible for the upper station.” The tram needed to connect to the ninth floor of the Kohler Pavilion, a major OHSU medical building. Complicating this was the fact that surgeons perform microsurgery within the pavilion, and even the slightest vibration from the tram could mean disaster during a surgery.

An electric motor, transmission, and bullwheel in the lower station power the tram

Designers also had to consider the logistics of building structures that could satisfy clearance requirements for the tram line between the upper and lower stations as well as over an interstate highway and two high-tension power lines. Additional considerations included environmental impacts and minimizing intrusions and disruptions to the residential area the tram would span.

Ready for Design Work
In March 2003, PATI awarded the overall design contract to Angélil/Graham/Pfenninger/Scholl, an architecture firm based in Los Angeles and Zurich, Switzerland. In November of the same year, PATI selected Doppelmayr CTEC to design, fabricate, and install the tram. Based in Switzerland and with offices in Quebec, Canada and Salt Lake City, Utah, Doppelmayr CTEC has installed aerial tramways and similar lifts using wire rope worldwide.

Several things became clear. Besides a base station, two very tall structures would have to be constructed: an intermediate tower at a distance 10 percent along the route to raise the tramline high enough to clear Interstate-5 and the public thoroughfares that lie between the two tram stations and a second set of tall massive struts to support the upper station, which interfaces to the ninth floor of the medical pavilion.

Since the intermediate tower is constructed on a flat surface with no surrounding buildings, this was a routine undertaking. Supported by 35 piers sunk deep into the ground, the tower stands 197 feet high with a base 22 by 20 feet wide.

The upper station was built on the top of tall struts on a hillside adjacent to a major medical facility, making construction more problematic. Ultimately, it too was anchored into the ground with deeply bedded steel-reinforced concrete. The tower and upper station struts are double-wall construction, the cavity filled with concrete to provide rigidity.

A skybridge to the medical pavilion would have to include a feature to prevent even the slightest vibration from interfering with surgeries taking place inside the pavilion. As the tram cabins slip into their bays, they nudge against the structures. Additionally, the skybridge itself frequently moves minutely. A flexible coupling was used to allow for the movement in the upper terminal while stopping vibration or movement from reaching the hospital building itself. Additionally, an aluminum plate on the skybridge floor provides a threshold for the floor to slide back and forth.

Mike Commissaris, general manager of tram operations, at one of the control room monitors, which show every aspect of tram operation

To power the tram, the system has three drives. The main one consists of a 536-horepower electric motor at the lower station operating off electricity supplied by city utilities. If any part of the main drive shuts down, the standby drive, a 12-cylinder diesel engine with three hydraulic pumps and a hydrostatic motor activates. Should this drive also fail, the manually operated evacuation drive can bring the cabins from the tramlines into the stations. Two tram cabins travel in unison along parallel steel track ropes measuring 1.93 inches thick and 3376 feet long and tensioned at 125,000 pounds, with one car at the lower terminal when the other is at the top. State-of-the art drive and braking systems move and stop the cabins.

According to Pearce, the tram fits in well with the city’s environmental missions. “It is very energy efficient, uses green power, and reduces the number of auto trips and greenhouse gas emissions.” Officials expect the tram to reduce gasoline usage by 93,000 gallons a year and greenhouse gas emissions by 1,000 tons.

Additionally, the tram can hold bicycles, and the lower tram station has dozens of bike corals and other fixtures for riders to lock their bikes. Bike riding has reportedly increased substantially since the tram began operating. OHSU provides incentives for bikers, and now that they no longer have to climb a steep hill, more of them pedal to work and classes.

The tram cabins were hand built by Gangloff Cabins in Switzerland and designed to look like clouds going through the sky. Each empty cabin weighs approximately 6.6 tons, with space to hold up to 78 passengers. The sides have a unique curved design.

Gathering Citizen Input
While engineers and architects worked through design and construction issues, the city of Portland focused on a totally different set of problems: Area residents were not happy that a tram would become part of their daily lives.

With doctors performing surgery in an adjoining building, tram cars must enter the upper station quietly and softly

“We went through a lengthy planning process that included discussions with neighborhood residents,” Pearce says, “but there was considerable opposition from some of the neighbors.” One group aggressively pushed against the project, and it became common to see anti-tram signs in windows, telephone polls, bulletin boards, and even on rooftops.

An area resident, Dr. Dan Hagg, an OHSU physician, relates that while he now thinks the tram is “wicked cool,” he objected to it in the beginning. “It was clear in the public meetings the city held that the board didn’t care what the neighbors thought, so it felt like there was a disregard for the impact it would have on us.” However, he rides it a couple of time to work every week and anticipates that once a planned pedestrian path is completed, he will ride it most days. “The tram is exceedingly convenient and fun. They put a lot of thought into the design so it doesn’t look or feel like a floating city bus.”

In this joint venture, OHSU, the city, and South Waterfront property owners funded the tram, and now it is owned by the city and operated by OHSU. It is open to the public and operated as part or Portland’s public transportation system.

While the tram project came in substantially over budget, and it came under attack in the media more than once, it is now a point of pride among many Portland residents. On a clear day, the view alone is worth the four-dollar round-trip ride. Hagg speaks for many riders when he says, “There is nothing like riding the tram on a clear day and looking north and south and seeing all the views the city has to offer. You can see Mt. Hood, Mt. Adams, Mt. Rainier, and all along the Willamette Valley. It’s absolutely fantastic.”
Nancy Hill is a freelance writer in Portland, Oregon

Progressive Engineer
Editor: Tom Gibson
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©2006 Progressive Engineer