Why is the citizens' only individual transportation a bicycle in The Giver?

Children are given bicycles at the age of nine, a rite of passage representing independence and responsibility within the community. From a reader's perspective, it seems like a hollow gift considering that members of the community are prohibited from leaving (the consequence being "release to Elsewhere," or death).
The freedom associated with bicycles, as conveyed by the Committee of Elders, is a stark contrast to the lack of control that the community members have over their lives. Thus, the bicycles can be interpreted as a symbol of limited freedom for the community members, rather than a true freedom.
Bicycles are a convenient form of transportation—convenient for the Committee of Elders to monitor and control, that is. They are a low-risk method of travel, they sustain the health benefits associated with exercise, and they do not present issues associated with pollution (as previously mentioned, maintaining a favorable external environment is a scientific priority within the community).
If a community member attempted to escape using a bicycle, it would be difficult to evade the search planes. This last detail plays into the ambiguous ending of the novel. Jonas and Gabe seemingly avoid the planes while traveling by bicycle into Elsewhere, and the novel ends when Jonas finds a sled (it is unclear whether this is real or from a similar memory passed down from the Giver).

Jonas's society is founded on the principles of Sameness, where every citizen must conform to society's standards and their lives are controlled by the Committee of Elders. It is also important to remember that the community's scientists have significantly altered the environment and climate to be completely comfortable and safe at all times.
In Jonas's community, there are no hills, rough terrain, or unfavorable weather. The citizens are also prohibited from leaving the community without permission, and transportation is extremely limited. Since the citizens are not allowed to leave the community, do not have to travel long distances, and do not have to traverse over difficult areas, they are required by law to ride bikes after the age of nine while traveling throughout the community.
The Committee of Elders, the ruling group, has decided that riding bicycles can be the only form of individual transportation within the community. This seems appropriate given the favorable terrain, pleasant climate, and the close proximity of dwellings and other buildings within the community.