Free riders

Felix Salmon supports Mayor Bloomberg's proposal to eliminate fares on some New York city bus routes. This has some advantages as collecting fares is expensive but there is a downside in that fares serve to screen out undesirable riders. This paper (pdf file) concluded:

Based upon the findings of this synthesis, it is concluded that a fare-free policy might be appropriate for smaller transit systems in certain communities, but is ill-advised for larger transit systems in major urban areas because experience shows that in larger systems, a tremendous amount of criminal activity, as well as a sharp increase in ridership, caused higher maintenance costs, labor costs, and operational costs and drove away existing riders.