Despite huge reductions of noxious emissions from factories and cars, Southern California's air is still terrible. It's so bad that the state is requiring that two percent of new cars sold in 1998 be zero polluters and ten percent by 2003. Many researchers here have become preoccupied with teh...

Public transit systems differ from many other government enterprises in that they charge a fee, or fare, in much the way that private businesses charge for their services. Transit fares are typically of two sorts: flat or differentiated. For decades transportation scholars have argued in favor...