here is at least somewhat explanation to the concern you have posted and might give you some explanation by user on another vw forum which is primary similar can be applied in Audi
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Like so many of the readers in these forums over the years, I had always wondered why VW (and other automakers) would go through the trouble of changing the rear turn signals from amber to red on some of their North American models. This practice has been especially prevalent over the last 10 years or so. If the USA and Canada allow either amber or red rear turn signals, while all of the rest of the world (outside of North America) mandates only amber rear signals, then why change them to red for North America in the first place?
The answer, in most cases, is actually a legal one. While the USA and Canada allow either amber or red rear turn signals, there is also a minimum size requirement in effect. This size requirement does not exist outside of North America.
The minimum size requirement applies to rear turn signals, as well as brake lights (even if the brake lights are not used as turn signals). This is a law that has been in effect in the USA (and Canada) since the mid 1950s. Back then, many vehicle models had very small tail lights, which could be hard to see until you were literally right up on them! So the US forced automakers to design bigger tail light assemblies, which were more visible to other drivers, by legislating a minimum size requirement. The size requirement is based on a concept called EPLLA (Effective Projected Luminous Lens Area), which states that the minimum illuminated size of a rear turn signal (or brake light) must be at least 50 cm squared (or 7- 3/4 in squared). If this size requirement is not met, then automakers are forced to change the rear turn signals in order to comply.
This is the case in certain models like the mk5 Rabbit/GTI, the mk7 Golf/GTI, late model Tiguans, and late model CCs, for example.
In Mexico, either amber or red rear turn signals are allowed, but there is NO size requirement like in the US and Canada. Therefore, some of the models sold in Mexico (like the mk5 GTI, and the mk7 Golfs) still have the original amber rear signals fitted for that market.
In all of the rest of the world (outside of North America), amber rear turn signals have been mandated by law for many, many decades. Just look at the old VW Beetle as an example. European versions were first fitted with amber rear signals beginning with the 1962 model year. Overseas, there is no size requirement for rear turn signals, as long as the signals meet legal requirements for brightness and light intensity. That is why automakers often use halogen bulbs, or even LEDs, for tail lights with smaller turn signal sizes.
US and Canadian laws are older, and do not take turn signal brightness into consideration. Instead, US law concentrates primarily on minimum illuminated size.
In some cases, however, the change is made in order to reduce the vehicle's selling price. Incandescent bulb lamps, or single color LEDs, are cheaper than Bi-color LEDs. Such is the case on mk5 Jettas, B6 Passats, and the Eos.
Statistically, amber turn signals are shown to be safer, because they are more quickly recognized by the human brain, from farther away, to be signaling lamps, especially if the brake lights are also illuminated. However, the minimum size requirement in the US and Canada does somewhat compensate for this at times.
But I'm not here to debate which setup is better. I simply wanted to educate everyone as to why automakers sometimes change the rear turn signals on their North American models.
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Originally Posted by tico
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