I think a colon would be the most apt punctuation here.
The tracks are now unruly and wild, the people tied to them: killed in crosswalks
But to be honest I was fine with no punctuation. The bit that most bothers me is the choice of preposition. You don't go in a crosswalk. You go on it. Or maybe you're at the crosswalk when you're killed. But certainly not in.
Grammar has so many "technically correct" yet odd sentence structures.
The sentence definitely has a weird flow and could absolutely contain reader assistance via punctuation.