A recent report from one of the world’s top transit thinkers analyzed data from U.S. cities to investigate the incremental costs and benefits of high quality transit service (defined as service sufficiently convenient and comfortable to attract travel that would otherwise be by automobile).
It indicates that high quality public transit typically requires about $268 in additional subsidies and $104 in additional fares annually per capita, but provides vehicle, parking and road cost savings averaging $1,040 per capita, plus other benefits including congestion reductions, increased traffic safety, pollution reductions, improved mobility for non-drivers, improved fitness and health.
This indicates that residents should rationally support tax increases if needed to create high quality public transit systems in their communities. (Other data shows that voters generally do.) Current planning practices tend to overlook or undervalue many of these savings and benefits and so result in underinvestment in transit quality improvements.
Check out the full report from the Victoria Transport Policy Institute, aptly titled: "Raise My Taxes, Please! Evaluating Household Savings From High Quality Public Transit Service." You can’t beat a pocket book angle on the need for high quality transit options being built in our community (and only 19 pages to read).
For those with more time or curiosity on their hands, VTPI also has a much more detailed "Transportation Cost and Benefit Analysis: Techniques, Estimates and Implications," a guidebook for quantifying the full costs and benefits of different transportation modes.