Most of our transportation modes have hit their speed limits. Our experience with the Concorde, and our inability to improve upon it, demonstrated that air travel is stuck at subsonic speeds for the foreseeable future. We might be able to get a few more miles per hour out of cars and motorcoaches, but not many. The biggest potential by far lies with rail travel in the U.S., where passenger trains outside Amtrak's Northeast Corridor are held to a national speed limit of 79 mph.
In parts of Michigan and Illinois, however, Amtrak has been working with the railroads and state governments to upgrade track and traffic control systems to permit higher speeds, most recently a bump from 79 mph to 110 mph on a 15-mile stretch between Chicago and St. Louis.
A top speed of 110 doesn't sound like much, and on the world stage it isn't much, but it's a 39% increase that offers the promise of more to come.
We'll take it, and then some.