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For a city content to bill itself as the most sustainable in America, there’s always a fair share of debate over just how useful Portland's public transit is.
Do people even use those MAX cars? Seems like somebody is always asserting that empty trains abound.
But in a recent advertisement, TriMet pulled out an interesting statistic: "MAX carries 30 percent of evening rush hour commuters traveling from Downtown on the Sunset and Banfield freeways."
Right above that statement is a photograph of bumper-to-bumper freeway traffic and a MAX train cruising down the rails along side it.
The fact along with the picture begs the question, so we asked it: How could that train possibly be carrying 30 percent of all that freeway traffic?
We sent an email to TriMet spokeswoman Mary Fetsch to see how the agency came up with this fact and she sent us one right back with the documents we needed -- and more. (If only everybody were so helpful when we came calling.)
Here’s how TriMet figured it out:
They picked two points for gauging the traffic (both car and MAX) leaving downtown Portland on either of the freeways they mentioned. For the Banfield they used Lloyd Center and for the Sunset they used Goose Hollow. Both of those points are MAX stations as well as traffic-counting stations.
For the MAX piece of all of this, they simply looked at what the average ridership was for a weekday between the hours of 4:30 and 5:30 p.m. (About 2,200 riders went eastbound and 1,600 went westbound.)
Counting the folks traveling by car proved to be a little trickier, but not by much. The Oregon Department of Transportation counts the number of vehicles passing by certain counting stations through loop detectors embedded in the roadway. The data is archived in a system housed by Portland State University, so TriMet could easily figure out the average number of cars running in each direction.
Now, a car is not the same as a person, so you can’t do a one-to-one comparison with these two sets of data. But TriMet realized that. To get the average number of riders per car, TriMet turned to the Federal Highway Administration’s "Summary of Travel Trends: 2009 National Household Travel Survey" (the most recent available).
According to that survey, the average number of commuters in a vehicle is about 1.13. They took that number and multiplied it against the number of cars counted by the transportation department. What they found was that about 4,600 commuters traveled eastbound by car and about 4,400 traveled westbound by car.
If you compare those figures with the MAX commuting figure, you find that TriMet is right on the money: About 30 percent of evening commuters along the Banfield and Sunset highways use the MAX. (In case you’re curious, the number is slightly smaller for the morning commute, but not by much.)
Now, we did have one other nagging question: Was that 1.13 passengers per car figure that TriMet used fair in the context of Portland? After all, Portlanders commute by bike more often than the national average, maybe the same was true for carpooling.
We can’t be sure based on the study TriMet used, because it doesn’t offer city-specific figures. But we’re in luck because the Census gives us some indication. According to the most recent Census data from the American Community Survey, about 9.2 percent of Portlanders carpool. That puts us about in line with the national average of 9.7 percent.
None of this tells us whether 1.13 is exactly right, but we do feel that given the parity in the Census, it’s fair for TriMet to assume something close to parity here, too.
In an advertisement, TriMet said the "MAX carries 30 percent of evening rush hour commuters traveling from Downtown on the Sunset and Banfield freeways." They were able to back up this claim with reliable data.
We rate this statement True.
U.S. Census, American Community Survey, 2011
Car Counts, Oregon Department of Transportation, fall 2012
E-mail from Mary Fetsch, spokeswoman for TriMet
Federal Highway Administration, "Summary of Travel Trends: 2009 National Household Travel Survey"
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