are designed to be ridden fast on smooth pavement. They have smooth, skinny tires and "drop" handlebars, and can be used for sportive endurance rides and on-road racing. They are usually lighter than other types of bicycles. They can be ridden on paved trails, but most people find them uncomfortable and unstable on unpaved trails.
Most road bikes are not capable of carrying heavy loads.
Flat-Bar Road Bicycles
have most of the advantages of regular road bikes--lightweight frames and relatively narrow tires for efficiency on pavement--with a flat or upright handlebar. These bikes are designed for people who want a light, high-performance bike, but don't like the drop-handlebar riding position of a regular road bike.
These bicycles are sometimes called fitness bikes or performance hybrid bikes. Most of them can accept somewhat wider tires, to make them suitable for use on unpaved trails.
They usually have the ability to mount cargo racks and fenders, which make them good commuter bikes.
Touring Bicycles
are another special type of road bike. They are generally designed to be ridden on pavement, and are more durable for use on self-supported long-distance riding. They have all of the necessary mounting bolts for cargo racks and fenders, and although they still have a drop handlebar, they usually have a more relaxed frame design so that the rider is more upright, for more comfort when riding long distances for multiple days at a time.
They have a lower gear range compared to regular road bikes, to allow for carrying heavy loads up steep hills.
They also make good commuter bicycles, because of their durability and ability to carry heavy loads.
Triathlon/Time Trial Bicycles
are road bikes with a special design that maximizes their aerodynamic properties. The handlebars are also a special aerodynamic design that allows you to crouch forward into a tucked position while riding, to minimize the wind resistance against your body.
Triathlon/time trial races usually have staggered starts, where each racer starts on his/her own; these bicycles are usually not allowed to be used in mass-start races.
Track/Fixed-Gear Bicycles
orfixiesare designed to be ridden on a velodrome, which is a banked oval track specifically for bicycle racing. Some commuters prefer track bikes, however, due to their simple design, which makes them easy to maintain.
They have a single gear that does not provide the ability to coast, so if the bike is moving, your feet must be pedaling. For even more simplicity, some riders prefer to not have brakes, since the fixed-gear mechanism can act as a brake. Most track bikes have drop handlebars, but some riders outfit theirs with flat or upright handlebars.