Single-speed bicycle on the situation, a messenger may prefer a mountain bike based single-speed, which can roll over many obstacles, or a fast and light road bike-based single-speed. In the United States market, bicycle companies such as Bianchi, Cannondale, Fuji Bike, KHS, Kona, Raleigh, Giant, Specialized, Swobo, Felt, Trek and Niner all have produced and marketed single speed bicycles. Because most full suspension frame designs either have a single pivot that is not concentric with the bottom bracket, or a linkage with a variable center of rotation, the distance between the bottom bracket and rear axle varies throughout the suspension's travel. This
Police bicycle 21st century there has been renewed interest in police bicycles, since they provide greater accessibility to bicycle and pedestrian zones and allow access when roads are congested. The bicycles are custom designed for law enforcement use. Many manufacturers of bicycles offer police models, including Volcanic Bicycle, Trek, Cannondale, Specialized, Fuji, Safariland-Kona, Force, and KHS. Other companies offer police, fire and EMS specific models. Many are equipped with a rear rack and bag to hold equipment. Police bicycles' pedals are almost always flat pedals, sometimes outfitted with toe clips/straps, to allow for normal shoes to be worn (versus cycling-specific shoes that