From their event page: 

The Philly Bike Train is an organized group bike ride for commuting to work, school, or another common destination.

We leave at a set time from the start, and you can join at the start or anywhere along the way, just like a regular bus or train. Use the tracker to catch the ride as is passes nearby you!

Bike buses are a more fun, social, and safe commute.

Ride with us to get where you’re going