Dim-Dip Lamps
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(UK Only)
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UK regulations briefly required vehicles first used on or after 1 April 1987 to be equipped with a dim-dip device[17]
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or special running lamps, except such vehicles as comply fully with ECE Regulation 48 regarding installation of lighting equipment.
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A dim-dip device operates the low beam headlamps
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(called
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"dipped beam" in the UK) at between 10% and 20% of normal low-beam intensity.
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The running lamps permitted as an alternative to dim-dip were required to emit at least 200 candelas straight ahead, and no more than 800 candelas in any direction.
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In practise, most vehicles were equipped with the dim-dip option rather than the running lamps.
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The dim-dip systems were not intended for daytime use as DRLs.
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Rather, they operated if the engine was running and the driver switched on the parking lamps
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(called
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"sidelights" in the UK).
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Dim-dip was intended to provide a nighttime
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"town beam" with intensity between that of parking lamps
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(commonly used by British drivers in city traffic after dark) and dipped/low beams, because the former were considered insufficiently intense to provide improved conspicuity in conditions requiring it, while the latter were considered too glaring for safe use in built-up areas.
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The UK was the only country to use such dim-dip systems.
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In 1988, the European Commission successfully prosecuted the UK government in the European Court of Justice, arguing that the UK requirement for dim-dip was illegal under EC directives prohibiting member states from enacting vehicle lighting requirements not contained in pan-European EC directives.
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As a result, the UK requirement for dim-dip was quashed.
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Nevertheless, dim-dip was
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(and is) still permitted, and while such systems are not presently as common as they once were, dim-dip functionality was fitted on many new cars well into the 1990s.
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