Violent crime in Greek cities is typically less common than in comparably-sized U.S. cities, but petty crime against tourists continues to be a nuisance. A far greater danger is traffic. Greeks generally pay little heed to traffic rules or safe driving practices, and poor road design adds to congestion and risks for pedestrians and drivers. In addition, Athens is on a building boom to prepare for the 2004 Olympics and traffic congestion has increased dramatically to become virtual gridlock in Athens and its suburbs. Greece has a substantially higher rate of serious car accidents than the U.S., and vehicle density in Athens is higher than in major U.S. cities.