The U.S. government has a hand in the transportation infrastructure of the United States, is is proven by the funding that Amtrak extorts every so often, and the fact that BNSF Railroad was merged by the government into what it is.
One this issue, it would lower the prices of goods if those who transport it don't have to pay as much in the way of fuel costs to ship it. As trains and trucks, as do most ships run on diesel fuel, a type of gasoline.
This would be good for the economy, and for peoples pocket books, as well as giving jobs to those who would build the new engines and so on. It would also allow Amtrak to better compete with such things as Airlines more effectively.