In the United States, an antique car is generally defined as a car over 25 years of age, this being the definition used by the Antique Automobile Club of America. However, the legal definition for the purpose of antique vehicle registration varies widely. 20 years is about double the design life of modern cars and an even greater increment on those cars now 20 years old; therefore, a car that's reached 25 is a Classic, these and Antique cars are often not economical to maintain as regular transportation.