Nickname for the 38 Geary bus that runs east-west in San Francisco. Geary Street runs from downtown and Union Square all the way to Point Lobos, a scenic ridge perched above and overlooking the Pacific Ocean.
The "Dirty Eight" is a highly-trafficked MUNI bus line, running through several different neighborhoods: Downtown, the Tenderloin, Cathedral Hill, the Western Addition, and the Inner and Outer Richmond districts.
The regular 38 is known as the "milk run" because it stops at every stop. Not only is it slow, but no draft gets created because the darn bus doesn't move fast enough to properly ventilate itself, even when all the windows are open. The milk run is the polar opposite of clean and nice-smelling. When it gets too stinky, some people get off the bus and start walking. It's better than passing out from the fumes. The Dirty Eight operates 24 hours a day. I wouldn't recommend riding it anytime after 8 PM.
The 38L (Dirty Eight Limited) hits like every 3 stops and is only slightly better than the milk run. If the homeless riders allow you to open the windows, it can get decent ventilation. The 38L doesn't run at night so if you miss it on the way back home, you're stuck with two options: sucking it up and braving the regular Dirty Eight, or finding another way home.
The 38AX (Dirty Eight A-Express) is a peak hour commuter bus for people who live in the Outer Richmond and work in the Financial District. It is consistently cleaner than the milk run or the Dirty Eight Limited.
The 38BX (Dirty Eight B-Express) is like the 38AX but it
serves the residents of the Inner Richmond district.
Since there are so many buses on the 38 line, commuters as well as a variety of foul-smelling subhumans use the dirty eight to move back and forth across the city. I've had to step off the bus a few times because the smell and the floor were so overpoweringly disgusting.
Once, a fellow rider told me about how he isolates the clothes he wears on the 38 so that they don't touch any part of his house. Apparently, he doesn't allow his bus clothes touch any of his furniture, walls, or floor. They go straight into the washer.
Thinking about that bus makes me dread the ride home tonight.