In the course of traveling to Super Bowl gatherings and other places on Sunday, a bunch of SEPTA riders noticed something peculiar:

They couldn't get there.

That's because several SEPTA train trips were canceled when engineers and conductors didn't show up to work.

Could there have been something else compelling going on Sunday that was pulling their attention from their jobs?

SEPTA spokesman Andrew Busch said mid-evening Sunday that he couldn't say what was behind the so-called call-outs — when workers call to say they will be out.

"Without knowing what's going on with a particular individual, it's difficult to say what the reason is for a call-out," he said. "It's hard to paint a broad stroke."

At least seven scheduled SEPTA train trips had been canceled because of manpower shortages, Busch said.

The canceled trips were on the following lines: Paoli-Thorndale, Chestnut Hill West, Lansdale-Doylestown, Wilmington-Newark, Del. Three canceled trips were on the airport line.

Busch said he couldn't say how many workers didn't show up for their trains. Nor could he say how many riders were affected.

He added that he didn't know precisely how many Sunday trips SEPTA runs. He did say there are 740 trips on weekdays, and that Sunday numbers are roughly 35 percent to 40 percent of that total, which would come to about 260 to 300 trips.

Asked whether he anticipated call-outs on Monday morning from workers who could have over-partied Sunday night, Busch said, "There is no indication of anything changing for tomorrow. We have a full weekday schedule planned for Monday."

Several riders contacted SEPTA on Sunday to say their trains had been canceled. Busch didn't have a tally of how many complained.

SEPTA's troubles may have been Uber's gain — at least for one Uber driver, anyway.

Jamerson Williams said he appreciated the uptick in business – "about 10 to 15 percent higher" than a normal day, he said. Whether that was due to the canceled trains, the festivities, or the rain, he wasn't sure.

But, he said, rides had been steady all day long.

Staff writer Caitlin McCabe contributed to this article.