State lawmakers in California are considering a bill that would raise the gas tax and/or raise the vehicle registration fees to mitigate the transportation causes of climate change. The revenue raised in Los Angeles County will go to "mass transit improvements and programs to relieve congestion." This reflects the increasingly local nature of transportation funding as the state and federal governments have less and less money to give to transportation projects. As transportation is a shifting to a quality of life issue as well as a mobility concern, local governments need to find money to pay for improvements.
This is not a U.S. phenomenon. In London, where a congestion charge is levied to enter the center city, the Mayor is planning on implementing a $50 per day charge on large vehicles to mitigate emissions and local air pollution. If this charge wasn't enough of an incentive to switch to a smaller vehicle, the small cars will also be exempt from the daily cordon toll.
Ultimately, such a patchwork of policies can be beneficial, but cities need to be aware of the competing interests and goals of their policies. Taxing large cars is a good idea, but a vehicle fee based on weight is probably a better approach than one that claims global environmental benefits. Also, congestion and environmental concerns share many potential solutions, but the costs and benefits cannot be traded between environmental policy and traffic management. Environmental incentives should not include any benefits for driving more, such as exempting small cars from the tolls or carpool rules (as is the case in California).
This isn't to say that these ideas are any worse than what might be proposed at the national or international scale. It is good that cities are taking the lead in traffic and environmental policy. Many cities trying many things will result in a choice of public approaches that will be more flexible than a string hierarchical mandate. Yet too often public officials try to solve every problem with one magic policy. Congestion is one issue, green transportation is another. There will be policy overlaps regardless of the policy scope, but both the California legislation (through new road construction to reduce congestion) and London's emission fees (by exempting small cars from the congestion fee) will have the perverse effect of increasing auto dependence and congestion. It's as though lessons learned are lessons forgotten.