Arash Guity can’t stop pedaling. That’s because the “fixie” bicycle he rides to work has no freewheel, which means there is no such thing as coasting. But Guity, a 34-year-old energy consultant, doesn’t see that as a deterrent. He welcomes the challenge of negotiating the terrain on his daily trip from Potrero Hill to his office in Union Square. He’s so attached to his mode of transportation that he also uses it in  … More