This is a good article. Has a lot of examples showing why streets have a good or bad pedestrian experience.
It's not as simple as number of lanes or even the quality of the sidewalk. A lot of it really comes down to development patterns. You can really feel the difference when you're in a place not built for walking. Being on a well constructed sidewalk far away from any buildings because there's a giant parking lot in between just feels wrong.
There are a few places very close to my house I refuse to walk to because the pedestrian experience is terrible. You feel out of place, unwelcome, and unsafe.