incandescent light bulbs in the lamps. Modern lamps and dynamos contain voltage limiters to solve this problem. Not suitable for high-power applications outside of lighting, unless designed to recharge an on-board battery. Bottle dynamos may be noisy, can be difficult to adjust, can slip under wet conditions, and may wear the sidewall of the tire Magnetic lights Lights can be self-powered via electromagnetic induction, eliminating the need for batteries or dynamo systems. The advantages are similar to those of dynamo lighting. The most common design includes a magnet on the wheel spoke and lights with a coil in them, mounted on the frame or fork of the bike. More exotic designs also exist; some have frame-mounted magnets and wheel-mounted lights, or a magnet and an inductor in one casing, using eddy currents. Supplementary lighting and visibility Headlamps Headlamps are a useful adjunct to bicycle lights. They can be pointed without steering the bike, giving useful fill-in lighting especially on poor or very dark roads. They have the added safety benefit of positioning the light higher on the cyclist for increased visibility. They also allow the wearer to read road and directional signs placed on high signposts. However, due to the high position of the light the glare may dazzle oncoming traffic. Some rechargeable systems offer a headlamp option powered from the main battery pack. Reflective and high-visibility materials Retro-reflective materials, in the form of fixed reflectors, reflective tape, and reflective clothing, are useful in making a cyclist visible to other road users. Reflective materials can be applied to bike, rider, or luggage; also, tires are available with reflective sidewalls. Reflectives are visible only when in the beam of a headlight, and even then only within a narrow locus. Importantly, they do nothing to light up the road. Reflectors are not a substitute for lights, but are an important supplement to portable lighting. On the bike Reflectors and reflective tape provide additional visibility (especially when applied to moving parts of the bicycle) and are mandatory in many jurisdictions. Pedal reflectors in particular are very visible to following traffic as they move up and down; unfortunately they are not compatible with most clipless pedal systems, although adaptors are available for some, mainly older SPD models, and a few single-sided designs are available with built-in reflectors. In the UK, where front and rear pedal reflectors are compulsory after dark, most cyclists with clipless