More recently, a particular form of wheeled transport, the railroad, has developed. Starting with Stephensons Rocket in the early 1800's, railroads have spread widely across the world, providing the backbone for the Industrial Revolution through their ability to move very large amounts of material at very low cost per ton-mile. While railroad technology has virtually stagnated in the United States in the last 50 years, train technology has continued to evolve in other countries, leading to high speed passenger trains that operate at 180 mph. However, further major improvements in railroads are not likely.

The two major new modes of transport to emerge in the 20th Century were the airplane and the rocket. While flying has been a dream of mankind for centuries, and was first achieved in lighter than air balloons by the Montgolfier brothers in 1789, it remained for the Wright brothers in 1903 to demonstrate practical heavier than air flight. Following their Kitty Hawk flight, airplanes developed rapidly, initially for warfare, and then for transport of passengers and high value freight over long distances, both land and water.

Like the railroads, airplanes have essentially reached a plateau of performance. Subsonic air transport has reached a maximum speed capability of ~500 to 600 mph. Supersonic air transport is not economically practical for the mass market. Subsonic planes have essentially reached a maximum practical size. The inherent problems of weather and airport congestion are increasingly causing flight delays, cancellations, and passenger discomfort. It is very doubtful that there will be any major improvements in air transport capabilities and costs. In particular, as energy costs rise, so will the cost of airplane travel.

Rocket transport, pioneered by Robert Goddard in the early 1900's, has proved to be of critical importance in modern warfare, space exploration, and satellite technology and communications. However, the very high cost of rocket transport - it currently costs approximately $10,000 per pound to put payloads in orbit, more than their value if they were made of gold - have kept rockets out of any mass market for transportation. Efforts are underway to bring down rocket costs through the use of reusable launch vehicles, but costs will have to come down by a factor of at least 100 in order to develop a mass market.