Introduced by luxury automakers a decade ago, the certified-used concept has been adopted by virtually every mainstream manufacturer and is

becoming a third distinct category of vehicle, somewhere between new and used, according to the Dallas Morning News.

Toyota was the first major manufacturer to get into certified used vehicles, in January 1996, and it is the leader today. Its dealers sold

42,699 certified used cars and trucks in the first year - a total that swelled to 196,926 last year.

Industry-wide, certified-used sales have grown from an estimated 50,000 or so six years ago to a projected 500,000-plus this year. Certified used vehicles generally sell in less than half the time that a traditional used car does, according to many dealers.

A typical used vehicle sold at a car dealership generates a gross profit of about $1,600, according to the National Automobile Dealers

Association (NADA).