A lot of drivers here, don't waits until the engine of their car warms up, and starts driving when the engine still cold, even in the winter (My father, my mother and my brother are such).
A light bar, have an array of LEDs with each LED located inside its own reflector, so the light gets concentrated efficiently. A SOX lamp is a single large light source, so it would have a single reflector for the entire lamp, and so it would be bulkier and less optically efficient.

Yea in that case an amber LED light bar would be a better choice in this particular application. Especially considering how expensive and relative fragility of SOX would be in automotive applications where NVH can be fairly severe. Not a good combo. 35w HPS would be of more interest as it has shorter warm up times and a smaller profile. I've run up a 35w hps on a Fulham workhorse and it even had instant restrike! The WH3 wouldn't take it up to full though, only ~20w. Maybe I'll try the 5 next time and see if I can get it to work better.

Experiments with special HPS lamps for automotive lighting, has done in the laboratories, but not reached into a commercial production.

Experiments with special HPS lamps for automotive lighting, has done in the laboratories, but not reached into a commercial production.

Over there I bet the winter temperature is not -40 either, that really makes people wait a few minutes for the car to warm up and gives you time to scrape the frost off the windows, and I was only bugging, I wouldn't really run the risk of damaging a LPS and the liquid sodium in a warmed up lamp would be all over the inside of the lamp with the amount of potholes we have over here..

But I have seen a farmer use HPS lighting on a combine running from a pure sine wave inverter and magnetic ballasts, long before LED light bars came out, as you age you lose night vision so they just get brighter lights and in the middle of field at 2 AM your not worried about other drivers you just need to see what you are doing, and pulling a few hundred watts off a 200 AMP alternator is nothing especially since the engine runs all night long or until the dew sets on the crops...   

Experiments with special HPS lamps for automotive lighting, has done in the laboratories, but not reached into a commercial production.

Would HPS headlights require a warmup time before they reach full brightness?  I can imagine the "flash to pass" feature would be an issue with bulbs that don't have instant full brightness. 

I noticed that some HID xenon headlights turn pink shortly before burning out.  My dad's old Lexus used bright white HID headlamps.  One day, one of the headlights turned pink and burnt out about a week later.  Is that just an HID phenomenon?