Stenciling says “6 & 7TH / PDE & 3RD” It’s the only pink tie on this track.
Just a stab in the dark but they may occur at regular intervals, and similar notation may be on the poles and other infrastructure. In the event of a rail emergency you give the operator that info and they will halt all trains that could be affected by the emergency
I was gonna guess a memorial like a union member passed or something, because it seemed odd it’d be pink and not orange or red like the little wireflags I usually see. Is there a pink infrastructure marker?
Pink is for surveyors.