That study seems to only look at Amtrak trains, so it doesn't consider the large number of subway or urban light rail systems in use. Amtrak has relatively few

That study seems to only look at Amtrak trains, so it doesn't consider the large number of subway or urban light rail systems in use. Amtrak has relatively few passengers (along with many other problems). The NYC subway system, for example, is far, far more fuel efficient than a car. As is probably any moderately used metro service.