Bicycles are very popular today in many countries . Many people use bicycles for exercise. But exercise is only one of the reasons why bicycle are popular. Another reason is money . Bicycles are not expensive to buy . They do not need gas to make them go . They also are easy and cheap to fix . In cities , many people like bicycles better than cars . With a bicycle, they never have to wait in traffic . They also do not have to find a place to park . And finally , bicycles do not cause any pollution