The Polish legal system is based on the continental legal system (civil law tradition). It has has been developing since the first centuries of Polish history, over 1,000 years ago. While Poland generally has a low rate of violent crime, the incidence of street crime, which sometimes involves violence, is moderate. Major cities have higher rates of crime against residents and foreign visitors than other areas. Organized groups of thieves and pickpockets operate at major tourist destinations, in train stations, and on trains, trams, and buses in major cities.