Collisions led to 1,000 deaths a year in a single two-block radius, one study found.
"The stoop is a threshold between private and public space."
The train station at Broad and Market (just west of City Hall) was originally built in 1881, then expanded upon by architect Frank Furness. It was razed in 1953.
At a groundbreaking ceremony this morning, Philadelphia Mayor Jim Kenney said the project reflected the city's diversity.