First, transportation accounts for about 50% of fossil fuel CO2 in Washington State; so it makes sense to direct 50% of carbon tax revenue to transportation. For a carbon tax of $30 per tonne CO2, that means about $1.15 billion per year, which sounds like a lot but in fact is just about perfect because…

Second, there is a huge unmet need for transportation maintenance in Washington State. The 2012 Connecting Washington report identified almost $800 million a year over the next 10 years in unmet needs just for maintenance of existing highways, roads, and bridges. Restoring transit funding to 2008 levels would bring the total to $1 billion a year over the next 10 years. Additional readings here include:

Finally, it makes political sense to connect carbon taxes and transportation infrastructure. Business, organized labor, and voters across the state place a high priority on maintaining the transportation system; but voters (especially in Western Washington) are concerned about the environmental impact of transportation spending, meaning that this is one of the few areas where environmental groups have political clout. We can leverage that political clout into a win-win outcome.