Lesson 17 Lighting System

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Lesson 17 Lighting System

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The lighting system of a motor vehicle consists of lighting and signalling devices mounted or integrated to the front, sides and rear of the vehicle. The purpose of this system is to provide illumination for the driver to operate the vehicle safely after dark, to increase the conspicuity of the vehicle, and to display information about the vehicle's presence, position, size, direction of travel, and driver's intentions regarding direction and speed of travel.

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1. Colour of light emitted Generally, lamps facing rearward must emit red light, lamps facing sideward and all turn signals must emit amber light (though in North America rear turn signals may emit either amber or red light), lamps facing frontward must emit white or selective yellow light, and no other colours are permitted except on emergency vehicles.

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2. Headlamps Forward illumination is provided by high("main", "full", "driving") and low- ("dip", "dipped", "passing") beam headlamps. Dipped-beam (also called low, passing, or meeting beam) headlamps provide a light distribution to give adequate forward and lateral illumination without blinding other road users with excessive glare.

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This beam is specified for use whenever other vehicles are present ahead. Mainbeam (also called high, driving, or full beam) headlamps provide an intense, centreweighted distribution of light with no particular control of glare.

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3. Fog lamps Fog lamps provide a wide, bar-shaped beam of light with a sharp cutoff at the top, and are generally aimed and mounted low. They may be either white or selective yellow. They are intended for use at low speed to increase the illumination directed towards the road surface and verges in conditions of poor visibility due to rain, fog, dust or snow.

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4. Position lamps Nighttime standing-vehicle conspicuity to the front and the rear is provided by position lamps, known as parking lamps or parking lights in North America which may emit white or amber light in North America; elsewhere in the world they must emit only white light. It is now illegal in many countries to drive a vehicle with parking lamps illuminated, unless the headlamps are also illuminated.

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5. Turn signals Turn signals — formally called directional indicators or directional signals, and informally known as "directionals", "blinkers", "indicators" or "flashers" — are signal lights mounted near the left and right front and rear corners of a vehicle, and sometimes on the sides, used to indicate to other drivers that the operator intends a lateral change of position (turn or lane change).

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In most countries outside North America, cars must be equipped with side-mounted turn signal repeaters to make the turn indication visible laterally rather than just to the front and rear of the vehicle. Turn signals are required to blink on and off, or "flash", at a steady rate of between 60 and 120 blinks per minute (Although som

e operate slower than this).

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International regulations require that all turn signals activated at the same time (i.e., all right signals or all left signals) flash in simultaneous phase with one another. Worldwide regulations stipulate an audiovisual telltale when the turn signals are activated; this usually takes the form of one combined or separate left and right green indicator lights on the vehicle's instrument cluster, and a cyclical "tick-tock" noise generated electromechanically or electronically.

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Turn signals are in almost every case activated by means of a horizontal lever (or "stalk") protruding from the side of the steering column, though some vehicles have the lever mounted instead to the dashboard. In virtually all left-hand drive cars, the signal stalk is on the left side of the column. In right-hand drive cars, the signal stalk may be on either side.

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If the vehicle's wipers are controlled by a stalk on the opposite side from the signal stalk, a driver unaccustomed to the vehicle may inadvertently activate the wrong control. Virtually all vehicles have a turn indicator self-cancelling feature that returns the lever to the neutral (no signal) position as the steering wheel approaches the straightahead position after a turn has been made.

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6. Tail lamps Night time vehicle conspicuity to the rear is provided by rear position lamps (also called tail lamps or tail lights). These are required to produce only red light, and to be wired such that they are lit whenever the front position lamps are illuminated—including when the headlamps are on.

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Rear position lamps may be combined with the vehicle's brake lamps, or separate from them. In combined-function installations, the lamps produce brighter red light for the brake lamp function, and dimmer red light for the rear position lamp function.

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7. Brake lamps Red steady-burning rear lights, brighter than the rear position lamps, are activated when the driver applies the vehicle's brakes. Outside North America, the range of acceptable intensity for a brake lamp containing one light source (e.g. bulb) is 60 to 185 candelas. In North America, the acceptable range for a single-compartment brake lamp is 80 to 300 candelas.< …… 此处隐藏：3376字，全部文档内容请下载后查看。喜欢就下载吧 ……