Hm. This is a good question...

[conuly]

About chirping intersections - do they only chirp sometimes? AND WHY DO WE NOT HAVE THEM IN NEW YORK? And on and on.

Comments

[wodhaund.livejournal.com]

Those are fantastic.

They're intended, as you may have guessed, for visually impaired people. (Which I say, because I have a friend who's colourblind who relies heavily on those chirps.)

They're supposed to chirp everytime - the ones in my area did - and there's a slightly different chirp for each direction; when one pair of lights is green, it's one chirp, and when the other pair is green, it's a different chirp.

I got so used to hearing them, that I started paying more attention to that than the colour of the lights, and now that I've moved back to an area that doesn't have them, I miss my "birdie-lights". ;;

[leora.livejournal.com]

Different areas use different types of disability-friendly lights. My favorite kind only chirps upon request. See my comment in the thread for a longer answer.