Thought I'd pop in and drop a quick idea...
I went to the MET this weekend to soak in a little culture. I was en route to the American Wing when I saw all these people sitting on these neat bars that ran along the length of each wall in the Egyptian section. I thought it was a very simple, space-saving seating arrangement and so useful as the MET is exhausting (my husband and I spent roughly 25 minutes looking at art and 45 minutes recovering on the benches in the front atrium...the chamber music was lovely.)
1,000s of cafe chairs have been steadily descending upon the pedestrian plazas throughout our great city, but maybe there is room for some diversity. I can totally see a ledge-like seat like this being easily implemented. Throw on some hooks so that we can hang our bags along the bottom and there you have it, an urban street seat. Here is a quick mock up...
I like it because it speaks of a quicker, more impromptu experience vs. a traditional bench. One isn't better than the other but this one feels a little "righter" for the streets. Plus they can serve as food cart parking spots throughout the city. Fun!