Most projects that receive federal funds require 20-25% matching funds. Those funds can come from any other source. Often there is some percentage of state funds, along with corporate or local dollars. There are sometimes provisions to permit in-kind services in lieu of cash.
As for trucks on I-81, on a recent trip, I was astounded at the number of rigs coming north as I was going south. In 15 minutes of counting every truck that passed, I reached 212. If that rate held for an hour, that would be 448 per hour. That's an awful lot of trucks roaring up the road at 70 or better!!