Its vertiginous single lane roads plagued summer after summer by traffic, the Amalfi Coast rolled out a new partial car ban on Wednesday. The region will be using an alternate number plate system, in this case meaning that only plates ending in an odd number can drive on odd number days and the opposite on even. The rules will affect the 22 miles between Vietri sul Mare and Positano. The new regulations will be in effect from 10 a.m. to 6 p.m. on weekends from mid-June through Sept. 30, the whole month of August, and Holy Week. Residents, public buses, and taxis are exempt. The road’s governing agency also banned automobiles based on certain lengths.