Rome, December 28 - Florence, Bologna and other Italian cities have joined Rome and Milan in implementing car bans to combat dangerously high smog levels. "Involving local authorities is the right choice," said Florence Mayor Dario Nardella after signing a vehicle ban until December 31 in the city centre. Nardella was referring to Environment Minister Gian Luca Galletti's decision to call a summit of mayors and regional governors in Rome Wednesday. Bologna and another four cities in Emilia Romagna including Modena halted city-centre traffic on Sunday. Regional Governor Stefano Bonaccini said smog levels had dropped sufficiently that it would "probably" not be necessary to go ahead with another blanket ban on January 3. Outside Milan, 13 of the 120 municipalities in the metropolitan area also enacted a three-day ban starting on Monday. Lombardy Governor Roberto Maroni said experts had told him such bans were "ineffective because there is an emissions spike when they end".