That means “riding black.” That is, using public transportation without having a ticket.

Or at least that’s what it used to mean before the Woke Folk took control of Berlin’s public transport operator. There are no racial connotations with this word unless you want there to be so now there are and that’s why its use has been verboten.
Berlin public transport operator BVG will stop using the German term “schwarzfahren” (or “blackriding”) to describe travelling without a valid ticket, it said on Friday.
The decision to discontinue using the expression, which is common in colloquial speech, implements a recommendation from the Berlin Senate’s diversity programme, a spokesperson told broadcaster rbb.

