Instead of squares, their streets intersect in diamonds, where the (largely one-way) streets come out of the corners. They're a bit larger than a square intersection-- it's like you took the square, and then filled in four right triangles at each of the corners.
The main effect is that crosswalks are significantly pushed back from the intersection center. As a pedestrian, there's far less ambiguity about where the cars are going (regardless of whether they use their signal). Same for drivers: you never have to wonder which way a pedestrian is gong to cross when they're standing at a corner where two crosswalks meet, because there are no such corners.
Of course, this also makes intersections much bigger. This is offset by having parking spaces along the edges of intersections.
