Yeah I thought it was pretty clear that ddeadserious wasn't on the sidewalk but coming from a street (or, apparently, an alley).

I have almost hit cyclists with my car in the exact same situation coming out of an alley - they're on the sidewalk, AND coming from the wrong direction on a one-way street. So not only does the angle around the buildings make it almost impossible to see someone going faster than walking speed on a sidewalk, you're not looking as closely in that direction anyway because that's not where car traffic would be coming from. I've taken to creeping veeeeerrrrry slooooowwwwly out of alleys when driving (as opposed to the speed out and honk your horn that other drivers like to do) and I still have had close calls.