Because of the high cost of converting existing rail - based lines , this is no longer done in Paris , nor elsewhere ; now rubber - tyred metros are used in new systems or lines only , including the new Paris Métro Line 14 .
Because of the high cost of converting existing rail - based lines , this is no longer done in Paris , or elsewhere . 
 Now , rubber - tyred metros are used in new systems or lines only , including the new Paris Métro Line 14 .