ZTL is an abbreviation of the Italian phrase Zona Traffico Limitato, which translates to "Traffic Restricted Zone". Given that many Italian historical towns are registered by UNESCO, almost all cities have traffic restricted zones. These zones prohibit entry to ordinary social vehicles, otherwise they will be subject to fines of varying amounts. Only registered vehicles such as buses, taxis, NCC (Non-Commercial Carriage) vehicles, and resident cars are allowed to enter.