If the physical design of the street says that it expects to be traversed at 40mph, people will drive 35 to 45mph on it even if the posted speed limit says 25.

If the physical design of the street says that it expects to be traversed at 40mph, people will drive 35 to 45mph on it even if the posted speed limit says 25. This situation offers tremendous benefits to traffic police officers a bit behind on their ticket writing, but minimal benefits for pedestrian safety, because the people likely to notice the sign and slow down were already the people likely to notice pedestrians and drive defensively.