Efficient Transportation

Last week's question: Are outdoor ice rinks really made with water? Is Zamboni a type of vehicle or a brand name?

• Yes, out door ice rinks are made with water. When I went ice skating last weekend, we talked about mixing some kind of chemical to raise the melting point of water, so it will freeze more easily. I suspect this will make it turn to liquid quicker under pressure though.
• Zamboni is a brand name, with their major competitor being Olympia. The latter is what Millennium Park uses.

This week's question: In physics, we often do problems where the ground has no friction, so there is no loss in energy. Now, imagine a world where the ground (and only the ground, not buildings or other artificial objects) have no friction. What would the transportation system in such a world look like? Hint: cars move because of friction between the tyres and the ground.