The bicycles are a symbol of independence, responsibility, and growing into adulthood for the Nines.
The bicycle, at Nine, would be the powerful emblem of moving gradually out into the community, away from the protective family unit. (p. 41)
Getting a bicycle at age nine is a rite of passage for children in the community. All children secretly practice on siblings' or friends’ bikes before they turn nine, so that they can ride off on their new bike on Ceremony day.
It was one of the few rules that was not taken very seriously and was almost always broken. .. But almost always, the older brothers and sisters had secretly taught the younger ones. (p. 13)
The bicycle is so important to the community because there is no other mode of transportation for most people. Although there are other vehicles, they are used for community purposes. Individuals ride bicycles to get around. Since the bicycle allows children to go places besides home, it moves them from a child’s home-based life to the community-based life they will have as an adult.
Bicycles are something we have in common with the community. However, in Jonas's world they are as tightly regulated as everything else.
Lowry, Lois (1993-04-26). The Giver (Newbery Medal Book). Houghton Mifflin Harcourt. Kindle Edition.
The bikes are the first step in gaining indepence from your family unit to becoming part of the community. It is one sign of the nines beginning to mature.