Hans Monderman is best known for his advocacy of shared space on roads, where signage and other regulations are removed so drivers, pedestrians and cyclists are forced to negotiate the space. A seemingly radical idea, shared spaces actually tend to flow better and are safer than conventional design. (There are not very many examples, however.)
Via Jalopnik, here is a natural experiment in shared space. An intersection in Budapest lost signals for a while and everybody figured it out. Not a perfect experiment, but suggestive nonetheless.