All practical maglev systems have powerful magnets mounted on the moving maglev vehicle. The magnets interact with a normal temperature guideway, generating magnetic forces that stably levitate the moving vehicle. Besides levitating the vehicle, the magnetic forces must counteract all external forces on the vehicle, such as head, tail, or cross winds, up and down grades, curves, misalignment or guideway loops, etc.

An important goal for maglev designers is to minimize the cost of the maglev system, so that it competes economically with other modes of transport. Of course, minimizing cost is only one goal. Other goals are safety (the primary goal), environmental friendliness, the capability to carry many kinds of heavy loads, operational simplicity and reliability, ability to operate in all weather conditions, ability to use existing rights of ways, and the capability to operate intermodally with other modes of transport.

Of the various maglev possibilities, systems based on superconducting magnets best achieve the above goals. Prior to Danby and Powell's invention of superconducting maglev, three types of maglev had been considered :

• Permanent magnets on the vehicle and guideway
• Electromagnets on the vehicle and an iron rail guideway
• Alternating Current coils on the vehicle and conducting sheets on the guideway