Tram energy efficiency is calculated based on tram ridership estimates and the elimination of the need for vehicle trips between Marquam Hill and South Waterfront.

Based on a study of program activities in the first OHSU building at South Waterfront, the Center for Health & Healing (CHH), it is estimated that a minimum of 1,538 round trip tram rides will be taken by OHSU employees, students, patients, and visitors on the average workday.

The Center for Health & Healing will house 900 daytime employees, including 550 people associated with the provision of medical care and 225 engaged in research and teaching activities.  In addition, 100 students will spend a portion of their day in this building.  It is anticipated that it will be necessary for 40 percent of the employees and 100 percent of the students to make at least one round trip to Marquam Hill each day.

In addition to students and employees working at the center, the building is expected to serve 2,380 patients and visitors daily.  It is estimated that 10 percent of these people will have reason to go to Marquam Hill to access additional diagnostic facilities or medical specialists.  Finally, there are 8,100 daytime employees on Marquam Hill.  It is estimated that 1 percent of these employees will travel to South Waterfront to access the wellness center, attend meetings or assist with patient care in the South Waterfront building.

Although exact hours have not been set, the 1,538 daily trips is a conservative estimate. They represent roughly 100 to 150 trips per hour, measured against a tram capacity of roughly 1,000 passengers per hour.  In addition, tram ridership is likely to grow significantly over the years as OHSU expands further at South Waterfront.  Initial ridership projections are based on Center for Health & Healing activities only.

Since a portion of OHSU operates 24 hours a day, 7 days a week, the assumption is that the tram will operate on weekends and holidays, with ridership expected at 10 percent of normal levels.  The tram will also close for two weeks of maintenance each year.  That means there are 261 normal workdays and 89 weekend/holiday days, or 350 days of operation annually, resulting in 415,106 round trips per year.

The round trip driving total between OHSU’s South Hospital and SW Gibbs & Moody, the location of the Center for Health & Healing, is 4.90 miles.  Over the course of a year, the presence of the tram will result in 2,034,019 vehicle miles per year that are avoided.

Assuming 2 million vehicle miles avoided, and the Oregon Department of Energy standard of 21.5 miles per gallon average vehicle fuel economy, the tram will save over 93,000 gallons of gas per year that would have been used if the tram weren't’ available.

In addition, the tram will keep over 1,000 tons of greenhouse gas (GHG) emissions out of our air. This is based on two factors described by the U.S. Environmental Protection Agency (EPA) in a report entitled "Greenhouse Gas Emissions from a Typical Passenger Vehicle".

The EPA report assumes that "annual emissions from a typical passenger vehicle should be equated to 5.5 metric tons of carbon dioxide equivalent" and that "the number of miles driven per year is assumed to be 12,000 miles for all passenger vehicles."

Based on those figures (and the fact that a metric ton is equal to 2,205 pounds), the average passenger car creates 12,127.5 pounds of GHG per year, or 1.01 pounds per mile.  With an estimate of 2,000,000 vehicle miles saved, it follows that the tram would prevent 2,020,000 pounds, or 1,010 tons of GHG from entering the air.