Fog lights don't produce enough beam throw to be of any genuine help much above 30 mph (though they do create a greater
feeling of security). There have been a few auxiliary low beams over the years. The only notable HID one was the Sylvania Xenarc X1010. It was massively overpriced for what it was when it was new, but it looks like
SUVlights still has some in stock since Sylvania divested themself of that product line. Taiwanese-made, private branded for Sylvania, no longer manufactured. If you ignore how SUVlights calls them "fog/driving lights" (no, they're auxiliary low beams), ignore the dangerous advice to rip out the bulb shield (if that nonsense is still on the SUVlights site — make sure you insist on getting units
with bulb shields), replace the "Exclusive D-HC light source" with a regular D1S (see if SUVlights will swap these out for you before sale; let someone else sacrifice 600 lumens for the pointless sake of a bluer light color), and aim the lamps carefully, you'll have a good street-legal set of auxiliary low beams. The beam pattern they produce is basically like that of a traditional SAE (US DOT) low beam: a central hot spot, offset slightly downward and rightward, with a spread of light to the left and right. When aimed and used correctly, they do give a very appreciable boost to your low-beam seeing without blinding other drivers.
Another good option, giving better performance than the X1010 Sylvania light, would be to mount a set of the self-contained Hella 90mm Xenon low beam projectors, which give a DOT-legal but European-type low beam pattern (sharp cutoff low on the left and high on the right with a "stair step" appearance). Ordinarily a completely ridiculous $600 apiece, but if you buy
just the projector itself (no ballast, no bulb), the
hardware kit and the
mount bracket, you can do a lot better (pricewise) on the ballasts (any D2R/D2S ballast will work) and on the
D2S bulbs. You could even put in
Philips "3000K" yellow D2S bulbs if that's your thing. Shop carefully and you could probably make this option come in pretty close in overall price to the Sylvania X1010 option.