This brings back memories of a similar discussion in a finance class a few years ago.<p>Someone suggested increasing the cost of using private automobiles (via higher tolls on bridges and tunnels, etc.), and making the subways and buses free (both to encourage ridership and to reduce the overhead required for collecting fares).<p>The professor responded that the first idea was good, since it would motivate changes in behavior, but it would have to be <i>a lot</i>, i.e., triple or more the current tolls, to really have an effect.<p>He thought the second idea made less sense b/c mass transit is an inelastic service to the population that currently uses it (i.e., people who ride the subway have no choice but to keep using it), and also since the cost of collecting fares is small relative to the overall income.