Took a year before I realized my Ridgeline had auto dimming / bright head lights. It didnt come with a paper manual so I never had the thumb through session as I only looked up online what I needed to know.
On the dashboard there is a green light with an A on it but no amount of fiddling around activated anything so I figured it was a generic dash and the feature wasn't implemented.
Turns out to activate the system you have to hold the lever back for 30 full seconds - not really something I'd do without knowing it prior and voila - It works pretty well on the flat.
My 93 Supercharged cougar has the same feature but it had a tuning knob in the mirror that made it easy to adjust.