The place where I am really pushed to write is one with a fairly mellow background level of stimulus -not so much as to completely overwhelm my senses, but not so boring either that it completely stalls all creative thought.
A bus that constantly moves through the neighborhood lets you can see new people, strike up conversation here and there, spot a few interesting cafes or enjoy the passing landscape . On a relaxed, sunny morning, Its never dull on a bus.
More than being stimulating, its also a good place to be productive. People are generally quiet and keep to themselves. Its never really rush hour on a suburban bus. They even have quiet rules on display. Its rather a cheap way to brainstorm out of office.
A library can do something similar too. Its a social setting where everyone is being productive. Of course, getting to the library needs commute, which ironically a bus doesn't. It literally picks you up from your nearest spot.
