Take your pick among credible urban planning organizations whose suggestions are more fleshed out than mine, but I'm happy to suggest some of the greatest hits:

Take your pick among credible urban planning organizations whose suggestions are more fleshed out than mine, but I'm happy to suggest some of the greatest hits: * Stop widening roads * Curb extensions * Circles * Diverters * Humps * Leave more roads unimproved * Prohibit cars from city centers entirely, as is often the case in European cities