Bicycles are a common mode of transport and a popular form of recreation. They can be used for touring, commuting to work or school, fitness, and racing. Some types of bicycles are adapted for use by disabled or elderly people, and children’s bicycles are designed to be safe and easy to ride. There are more than 1 billion bicycles in the world. The bicycle was invented in the 19th century. It was initially intended as a means of transport, but it became a popular form of recreation and helped bring about societal changes, including healthier lifestyles, decreased dependence on cars, and reduced traffic congestion.

The basic structure of a bicycle has changed little since the first chain-driven model developed around 1885, but there are many specialized designs for different types of cycling, such as racing, mountain biking, and recreational riding. The frame is the main component of a bicycle and sets the stage for how well other parts, such as the pedals, handlebars, and tires, will function. The quality of the frame, its geometry, and its material also contribute to the overall riding experience.

In general, bicycles are built for comfort and speed. Most have a suspension system to absorb shocks from riding over rough terrain. This helps reduce the amount of energy a person has to exert when riding, but can add weight to the bike. Other comfort features include padded seats and handlebars. Bicycles can be equipped with lights to increase visibility at night. Some have brake levers that can be activated by hand to stop the bicycle and allow a person to change direction without using both hands on the handlebars.

There are a wide variety of bicycle tire sizes and styles, including “skinny” tires that are narrower than standard bike tires. Some bikers prefer these tires, which give them a more aerodynamic profile and are easier to control at high speeds. There are also tires that are designed to be puncture-resistant, which can help protect against flat tires in the event of a crash.

Bicycles can be equipped with various accessories, such as baskets and racks to carry items. They can also be modified with a range of lighting and reflectors to improve safety. When riding a bicycle on the road, bicyclists should obey all state and local traffic laws, wear a helmet, bright clothing (during the day), and reflective gear at night or in poor weather conditions. They should stay away from pedestrians and stand off the roadway if possible, except to pass. When a bicycle lane is not available, bicyclists should position themselves several feet into the travel lane so that motorists can see them and know they need to move over to the left to let them by. In some cases, if the lanes are very narrow, cyclists may choose to take the entire lane. This practice is called lane sharing. It is not as dangerous as it might seem, because drivers usually slow down to a reasonable speed when passing bicyclists and do not pass them unless they have a clear view ahead of them.