text: United Kingdom – The Pedal Cycles (Construction and Use) Regulations 1983 require pedal cycles "so constructed that one or more of the wheels is incapable of rotating independently of the pedals, be equipped with a braking system operating on the front wheel"; riding a rear-wheel drive, fixed-gear bicycle with no front brake on public highways is illegal. Following the conviction of UK cyclist Charlie Alliston, who knocked over and killed a woman whilst riding a fixed-gear bicycle with no front brake, the UK Government announced a review of the laws covering "dangerous cycling" in September 2017. A brake on the rear wheel is only required for free-wheel bicycles.
  United States – The use of any bike without brakes on public roads is illegal in many places, but the wording is often similar to "...must be equipped with a brake that will enable the person operating the cycle to make the braked wheels skid on dry, level and clean pavement..." which some have argued allows the use of the legs and gears. The retail sale of bikes without brakes is banned by the U.S. Consumer Product Safety Commission – but with an exception for the "track bicycle" (...a bicycle designed and intended for sale as a competitive machine having tubular tires, single crank-to-wheel ratio, and no free-wheeling feature between the rear wheel and the crank...).
  Conversion
  Many companies sell bicycle frames designed specifically for use with fixed-gear hubs. A fixed-gear or track-bike hub includes special threads for a lockring that tightens in the opposite (counter-clockwise) direction compared with the sprocket. This ensures that the sprocket cannot unscrew when the rider "backpedals" while braking.