Sorry for not looping back earlier, it's from http://www.usgovernmentspending.com/united_states_total_spen... which is getting its data from a few sources but I think for the transportation piece you can look on page 125 here http://www.gpo.gov/fdsys/pkg/BUDGET-2012-BUD/pdf/BUDGET-2012... but may want to cross-reference with the other sources.