A few examples: Toyota Corolla 2014 and some number of subsequent years (which right there is kind of enough of an answer, because they sell zillions of them), Chevrolet-GMC C/K pickup trucks and Suburban-Yukon SUVs '95ish to '00 and then '09ish to a couple of years ago. Chevrolet-GMC full-size vans changed from turn signal DRL to low beam DRL in...might have been '08 or so. Chevrolet Astro - GMC Safari from '95 or so. Recent/present model Ford F-series pickups (another very high volume vehicle) except in the very high-spec fancy trims. Almost every '95+ Volkswagen and Volvo until they changed to dedicated DRLs a few years ago. Every Saab '95ish til the bitter, sad end except that silly rebadged Saturn SUV and maybe one other model, possibly the rebadged Subaru (9-2x). All or almost all Subaru models starting in '00 until '05ish.
The European-style white LED DRL is becoming much more prevalent in the USA, but there are still plenty of headlight DRLs (or too many, depending on your perspective) and a fair proportion of them are low beam.
Why does 50% voltage get 10% intensity? Filament bulb operating characteristics react exponentially to voltage change, not linearly. The exponents to approximate the changes are:
1.6 for power (wattage)
3.4 for output (lumens or candlepower)
-13 for life (hours -- yes, that is a "minus" before the 13!)
In the US rules, headlight bulbs are rated for output and wattage at 12.8v, and life at 14.0v So let's make the math easy and say we're starting with a 9006 bulb that produces 1000 lumens at 12.8v and has a 1000-hour lifespan at 14v. We want to figure out what it will do when it is fed 6.4v.
The math works like this:
[(operating voltage) ÷ (rated voltage)]^exp
So let's try it, first putting in the 3.4 exponent for lumen output:
[(6.4) ÷ (12.8)]^3.4
[0.5]^3.4
gives us 0.095. That's what we have to multiply the rated output by, to get the output at the new voltage. As you can see, we will be multiplying by a little under...ten percent!
We can also check what this 6.4v feed will do to the wattage:
[(0.5)]^1.6
gives us a multiplier of 0.33, so our wattage goes from a nominal 55 to about 18.
And for life:
[(6.4) ÷ (14)]^-13
[(0.457)^-13
gives 26262: yes, that really means the life of the filament will theoretically be 26,262 times longer than if it is run at 14.0v. That doesn't actually happen because of other factors that affect bulb life, but you can see the very steep effect on life of changing voltage.