Tricycles are an effective alternative to regular bikes for children and older people alike. They are great for people who have balance issues because of the two wheels in the back. The two wheels give the entire bike a lot more stability.
In addition to being stable, there is less of a chance of a person without a fantastic sense of balance faling over. The two rear wheels with the front wheel create a stable tripod that moves.
One of my favorite memories of vacationing in Hilton Head is of my grandmother riding a tricycle around the many bike paths with us. She had always insisted she could ride a bike but hadn't done so in many years. It was terrifying watching her fall on a bike multiple times before she spotted the tricycle. Once we got her the tricycle, she was able to go with us everywhere.
In conclusion, tricycles are an excellent way for older people to get out of the house and get some exercise with less of a risk of them falling and breaking a hip.