Cycles of all sorts

Under the International Vienna Convention on Road Traffic (1968) of the United Nations, a bicycle is defined to be a vehicle. Article 44 of the Convention stipulates that: "Cycles without an engine in international traffic shall: (c) Be equipped with a red reflecting device at the rear and with devices such that the cycle can show a white or selective-yellow light to the front and a red light to the rear." In some countries, for example France, it may be an offence to even sell a bicycle not fitted with legally compliant lighting system. However not all countries impose this requirement on their domestic cyclists.

Many jurisdictions require bicycles to be fitted with reflectors at point of sale. In the United States this is regulated by the Consumer Product Safety Commission. CPSC compliant reflectors (also commonly fitted in other markets) have three retro-reflective panels positioned at 30° angles. The standard requires a forward facing white reflector on the front of the bicycle, sideways facing white reflectors on each wheel, a red reflector mounted on the rear, and yellow reflectors mounted on the front and back of each pedal. Some interpret this as an endorsement of reflector-only night cycling.

Many jurisdictions require the use of a headlight and a rear light or reflector after dark. Individual jurisdictions define specific legal requirements in terms of light output and the size of lamp and reflector lenses, compliance with specified standards or they may simply stipulate a minimum distance from which any lighting device should be visible. Some jurisdictions mandate standards which make some safe and practical systems (usually involving LED based flashers) illegal (though those rules are rarely enforced). Most European countries require front and rear lights at night, as do some US states; others allow reflectors only at the rear.

Depending on one's jurisdiction, blinking lights may be forbidden on the grounds that a blinking light is only allowed on an emergency vehicle.

In the UK the law requires a light approved to BS 6102 Part 3: 1986, but allows the use of additional non-standard lights; in practice this means that users of powerful rechargeable systems need to add an additional light to meet legal requirements. Recent changes mean that a flashing LED may be used, but only if it has no steady mode. National cyclists' organisations such as LAB (US) or CTC (UK) are a source of lighting information.