Who takes BART out to the Ball Game?

October 9, 2012 Say what you will about the experience of riding Bay Area Rapid Transit (BART), but the agency collects fantastic data.

What BART riders pay for each trip is based on distance, and the fares are all calculated electronically, so the agency has a massive record of trip behavior by origin, destination, time and date. BART also notes happenings that affected ridership, such as major concerts, festivals, and sporting events. If you need to know the "bump" in ridership the night Lady Gaga sold out the Oracle Arena, BART can tell you.

And if you're a curious student and ask nicely, sometimes they'll share.

Browsing some of these data for a class congestion management study, I kept coming back to the sporting events. AT&T Park (home of the SF Giants) is well served by transit, and the Athletics' Oakland Coliseum is literally across the street from a BART station. It seems reasonable that baseball fans, even visitors from out of town, would take BART to a baseball game. But what visiting team inspires the biggest bump in BART ridership?

BART's "bumps" are the uptick in ridership at the stations nearest the baseball stadiums that can't be explained by regular ridership trends. I divided each bump by the stadium attendance for that day's game. So if 10,000 people showed up at a ballgame, but only 3,000 extra people rode BART (0.3), that would be less impressive than a game with 5,000 attendees where 2,500 extra people rode BART (0.5).

I calculated this ratio for every Giants and A's home game of the 2010 and 2011 regular season. I averaged the ratios across visiting teams to get a transit ridership rate by team.

Certainly correlation is not causation, many other factors affect ridership, this is only two year’s worth of data, and there’s no consideration of weather, time of day, or day of week. But both teams are in the playoff, and for bragging purposes, it's worth knowing if one's favorite team does better than their opponent.

A's fans are far more likely to take BART to a Giants game than Giants fans are to an A's game. This is strange, until you consider that the A's stadium is swaddled in parking. Maybe the Giants fans take it as an opportunity to tailgate?

What’s up with these Yankees fans? If anyone should be accustomed to taking transit, you’d think it would be those who root for the Bronx Bombers. Anecdotally, a fair number of Bay Area residents lived in New York at some point. They may cheer for the visiting team, but be local enough to live in the Bay Area and own a car. The other New York team, the Mets, correlate with higher transit ridership as expected.

But both the Giants and the A’s are hosting playoff games today, so the important question is: Does transit ridership correlate with a win for the home team? If you average the ridership rate of winning games versus losing games, it's about even in Oakland. But in San Francisco, the Giants actually do a bit better with higher BART ridership. In a sport so famously obsessed with luck, maybe riding transit will become the next great superstition.

Photo of Stomper courtesy of the Oakland Athletics.