Apparently it's not that new a thing (Mercedes have done it for a while and some others) but I've only recently been noticing it and what it is... When turning or indicating the corresponding fog light comes on too.
Is it just me or does it look silly, like you've put your fog lights on but one doesn't work and that it it's not so easy to see their indicator when approaching? I've nothing against a proper cornering light, but using the fog light seems/looks a little cheap and a somewhat half hearted effort.
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Cars...
'93 Audi Coupe 2.0 Alpine White (sold)
'99 Audi S4 Merlin Purple - K04 upgrade to 412hp (sold)
'00 Audi S8 Agate Grey (Sold

)
'11 Audi Q7 4.2tdi Unknown Red (Classic Red Pearl Effect - thanks MJ)