Not too long ago, nearly every car and truck built in America was built with body-over-frame construction, real wheel drive, and symmetrical designs. Today, most cars do not have a separate frame; instead, the frame and body are built as a single unit, called a unibody. In 1977,
when most cars were built on a frame, the average weight of a car was 4,500 pounds (16,800 kg). Today, because of unibody construction and changes in materials, the average weight is 3,000 pounds (l,l20 kg). Most trucks are still built on a frame. Another major influence on design was the switch from rear-wheel drive to front-wheel drive. Making this switch accomplished many things. The most notable benefits of front-wheel drive are improved traction for the drive wheels, increased interior space, shorter hood lines, and a very compact driveline. Because of the weight and loads pickup trucks are designed to move, they remain rear-wheel drive. Perhaps the most obvious design change through the years has been in body styles. Body styles have changed in response to the other design considerations and to trends
of the day. For example, in the 1950s America had a strange preoccupation with the unknown, outer space; this led to cars that had rocket-like fins. since then fins have disappeared and body styles have become more rounded to reduce air drag.
Not too long ago, nearly every car and truck built in America was built with body-over-frame construction, real wheel drive, and symmetrical designs. Today, most cars do not have a separate frame; instead, the frame and body are built as a single unit, called a unibody. In 1977, 
when most cars were built on a frame, the average weight of a car was 4,500 pounds (16,800 kg). Today, because of unibody construction and changes in materials, the average weight is 3,000 pounds (l,l20 kg). Most trucks are still built on a frame. Another major influence on design was the switch from rear-wheel drive to front-wheel drive. Making this switch accomplished many things. The most notable benefits of front-wheel drive are improved traction for the drive wheels, increased interior space, shorter hood lines, and a very compact driveline. Because of the weight and loads pickup trucks are designed to move, they remain rear-wheel drive. Perhaps the most obvious design change through the years has been in body styles. Body styles have changed in response to the other design considerations and to trends
of the day. For example, in the 1950s America had a strange preoccupation with the unknown, outer space; this led to cars that had rocket-like fins. since then fins have disappeared and body styles have become more rounded to reduce air drag.
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