This is a Muni seat. It is constructed of hard slick plastic.
One problem with the hard plastic seats on the buses is that when you combine it with body heat, moisture or condensation can form on the seat bottom. It's kind of like the unspoken fact of riding Muni.
It's funny, because when you are riding on crowded buses you can actually see people check for "Seat Moisture" before sitting down in a seat that someone just vacated. You have to do this very nonchalantly as you do not want to cause attention to why you may have chosen not to sit down.
Recently I was on the Muni bus. I was seated at the rear of the bus facing forward. The row in front of me was reversed so the male passenger in that row was facing me. At one of the stops three loud teenage girls boarded the bus. One of the girls sat next to me, one sat next to the other gentleman, and one sat across the aisle all while still carrying on their conversation.
The girl next to me pulled out a bottle of nail polish and told the girl sitting across the aisle to come sit on her lap so that she could finish painting the girl's nails who was sitting next to the gentleman. If you have ever been near an open bottle of nail polish you know how intense the smell can be.
And here is where "Nonchalant" went out the window.
Clearly annoyed by the loud girls, the gentleman rolled his eyes and decided to get up and move to the front of the bus.
The girls did not take kindly to this. They immediately rolled their eyes back and said "Ugghh."
With the newly vacated seat available the girl who was sitting next to me told the girl on her lap to move into the gentleman's old seat.
Crisis...there was body moisture on that seat!
So in the loudest possible voice lap girl says, "Ooooooh....ewwwwww....I ain't sitting there! Look at all that booty sweat! That's just gross!"
It took everything in me not to burst out laughing!
The Song Of The Day - Gonna Make You Sweat (Everybody Dance Now) by C & C Music Factory