We took a 61 from CMU, arriving downtown shortly before 5, and got to the 10th & Penn stop (which is only a stop for the ML) at roughly 5:05. This gave us a prime view of the antics of idiot drivers, who had decided that rush hour would be a great time to drive in dahntahn. Around 5:10, a woman approached us and asked if we were waiting for the Millvale bus. Yes, we were; she held up one finger, apparently to signify that there was only one ML run.
Penn was atrociously backed up westbound until maybe 5:25, with morons blocking the intersection at almost every cycle; eastbound not so severely. A seemingly endless stream of buses slowly approached on Penn only to turn, presumably onto the Ninth Street Bridge. The other person waiting left the stop and walked towards Ninth Street. We assumed she had given up and was going to catch another bus to Millvale.
Almost half an hour after the appointed time, we gave up and decided to walk to Station Square, where excellent restrooms can be found. Before we had reached the end of the block, the woman came running towards us, yelling "the ML bus is coming!" We turned around and reached the corner a few seconds before the ML (the ML) pulled up. I was afraid the driver (who was, after all, about 30 minutes late) would leave without our savior, and so I straddled the bus door to give her time to catch up. (This caused the driver to mutter something like "get on or get off, we're going!") Then we were off.
I should pause here to explain the significance of the ML bus, which is probably unclear. "ML" to us (but not to you, unless you're a functional programming freak) refers to the family of programming languages (Standard ML, Ocaml) known collectively as ML. (To the AI community, it means "machine learning". One wishes that automobiles would learn not to drive in downtown at rush hour, since their drivers show no sign of figuring that out.)
Unfortunately, we may have gotten off at the wrong stop. When the bus pulled off to the right, I thought we had reached the Millvale Loop, and got off. This was a disappointment. Unlike the Avalon Loop, it showed no sign of being a former streetcar loop -- not that there would necessarily be any sign, but it was just a parking lot. It seems possible that the Millvale Loop is further on, which explains why turning left out of the parking lot sent us back the way we came, instead of to the Shop 'n Save Market (which we suspected might have restrooms). Further investigation, probably via the 1F, appears necessary.
As we left the parking lot and stood on the sidewalk contemplating our next move, a large vehicle (possibly driven by one of our fellow passengers) pulled out of the lot and hit a large bollard, showering the sidewalk with reflector detritus. We were standing at the edge of the blast radius and were unharmed.
All hail the ML bus.