pedals are therefore riding illegally. The law is rarely if ever enforced, but could potentially be used in court to reduce financial compensation if the cyclist were to be hit by another vehicle. The CTC have suggested that the requirement should be waived if the cyclist fits an additional rear reflector or lighting, but this was not changed in the last revision of the UK vehicle lighting laws (which permitted flashing LEDs). Riders of recumbent bicycles have pointed out that the pedal reflector requirement is nonsensical for them, since the reflectors point straight up and down in use, and are invisible from other vehicles. As of 2008, California law allows white or yellow shoe reflectors (front and back), or reflective ankle bands, in lieu of pedal reflectors. Clothing On dark roads, retroreflective materials such as 3M's Scotchlite will show up boldly in car headlights. The colour of lighting should be checked in the rider's surroundings. A single solid colour can disappear under artificial light, particularly yellow sodium vapour lighting, and colour blindness is common; red/green colourblindness can make yellow fluorescent vanish against a green background (hedges or grass), although people with red/green colourblindness dispute this. Vests with both yellow and orange fluorescent areas plus wide strips of reflective may be the best solution. In recent times electroluminescent clothing has become available to add to the existing array of LED-illuminated armbands and helmet blinkies. Wheel-mounted lights Wheel-mounted lights are used to improve the visibility of a bike from the side. Due to persistence of vision, individual lights mounted on the moving bike’s wheel spokes are perceived as glowing arcs or circles. There are lights controlled with MCU that are capable of rendering colorful patterns or animations. The glowing rims or wheels can isolate the bike from the visual noise of the city lights and help drivers see and immediately recognize a cyclist. Such lights are mainly battery-powered, but battery-free designs also exist. Measures of light output Electric power consumption in watts The watt (W) is the unit of power, and is usually quoted for the electrical power input, not the light power output. Electrical power is the product of voltage and current (watts = volts × amperes). Input power is only useful when comparing lights of similar technologies. Luminous intensity in a given direction in candelas The candela (cd) is the SI unit of luminous intensity, that is power per unit