Japan is building the ultimate high speed rail system. The train uses magnetic force and actually floats above the track when running, practically eliminating the kind of wear-and-tear of traditional trains that scrape along metal tracks. So the trains last longer. The speed? Over 300 mph. Think about that.
The cost? Billions of dollars. (A 320-mile route would cost Japan around $112 billion.) The time to build the infrastructure? Years. (The 225-mile route that Japan is building is going to take 16 years.)
Do we have the money or the patience for this? No.
Like lots of innovations, though, perhaps the cost and building time will go down eventually. For now, it's fun to think about how quickly we could travel going that fast!