Infrastructure changes are like environmental changes--they lead to all sorts of unanticipated outcomes.  Countries that have imposed heavy tolls on cars and driving find that this does, indeed, encourage people to find alternatives to use of their cars.  All well and good as long as satisfactory alternatives exist (only really possible in larger cities with concentrated population bases).  But they also find that revenue related to cars (gas and retail sales taxes, licensing fees, existing toll revenues, etc.) drops, offsetting the new revenue projections.  This leads to absurd situations such as charging higher per mile tolls on green vehicles than non-green ones, which claws back some of the benefits (e.g. grants, lower retails sales tax, lower licensing fees, etc.) extended to them in the first place (the reasoning being that there is still some overall benefit to going green, just not as much as originally anticipated).  Road tolls also discourage tourist revenue.