We just got our son a "big kid" bicycle. After he helped me with putting on the training wheels, we went out for a ride around the park.
While out there, I envisioned him getting older riding his bike. I can see him riding around the park, while we play there. Then when he is older, I can see him riding his bike with his friends through the complex. Then I can see him riding around the block, not crossing the streets, when he is a little bit older.
I think that this is one of the major milestones of childhood, where they become more independent.