Sequential turn signals with OLEDs
Sequential turn signals are a feature on some cars wherein the turn-signal function is provided by multiple lit elements that illuminate sequentially rather than simultaneously: the innermost lamp lights and remains illuminated, the next outermost lamp lights and remains illuminated, followed by the next outermost lamp and so on until the outermost lamp lights briefly, at which point all lamps extinguish together and, after a short pause, the cycle begins again. The visual effect is one of outward motion in the direction of the intended turn or lane change. Sequential turn signals have been factory-installed only on cars with red combination stop/turn lamps. They were factory fitted to 1965–1971-model Ford Thunderbirds, to 1967–1973 Mercury Cougars, to Shelby Mustangs between 1967 and 1970, to 1969 Imperials, to the Japanese-market 1971–1972 Nissan Cedric, and to Ford Mustangs since 2010.
Two different systems were employed. The earlier, fitted to the 1965 through 1968 Ford-built cars and the 1971–1972 Nissan Cedric, employed an electric motor driving, through reduction gearing, a set of three slow-turning cams. These cams would actuate switches to turn on the lights in sequence. Later Ford cars and the 1969 Imperial used a transistorised control module with no moving parts to wear, break, or go out of adjustment.
FMVSS 108 has been officially interpreted as requiring all light-sources in an active turn signal to illuminate simultaneously. However, the 2010 and later Ford Mustangs are equipped with sequential turn signals.
see http://www.linhongled.com/auto-head-led-lights/led-auto-front-turning-bulb/ for signal light
Until the early 1960s, most front turn signals worldwide emitted white light and most rear turn signals emitted red. The auto industry in the USA voluntarily adopted amber front-turn signals for most vehicles beginning in the 1963 model year,though the advent of amber signals was accompanied by legal stumbles in some states and front turn signals were still legally permitted to emit white light until FMVSS 108 took effect for the 1968 model year, whereupon amber became the only permissible front turn signal colour. Presently, most countries outside of the United States and Canada require that all front, side and rear turn signals produce amber light. Exceptions include Switzerland and New Zealand.
In Canada and the US the rear signals may be amber or red. American regulators and other proponents of red rear turn signals have historically asserted there is no proven safety benefit to amber signals, though it has been recognized since the 1960s that amber turn signals are more quickly spotted than red ones.International proponents of amber rear signals say they are more easily discernible as turn signals,and US studies in the early 1990s demonstrated improvements in the speed and accuracy of following drivers' reactions to stop lamps when the turn signals were amber rather than red.
A 2008 US study by the National Highway Traffic Safety Administration (NHTSA) suggests vehicles with amber rear signals rather than red ones are up to 28% less likely to be involved in certain kinds of collisions, and a 2009 NHTSA study determined there is a significant overall safety benefit to amber rather than red rear turn signals.
There is some evidence that turn signals with colourless clear lenses and amber bulbs may be less conspicuous in bright sunlight than those with amber lenses and colourless bulbs.