Fitting Cars to a Growing Population

By Tom Ripley

Americans are getting bigger. Actually, that's putting the nicest face on the issue.  Americans are really getting fatter.  In fact, nearly one in three Americans meets the American Medical Association's classification of "obese."  And that has implications for vehicle designers, who must fit cars to an increasingly diverse population of drivers and passengers.
 
Consider these facts: in 1962, a woman weighing 199 pounds ranked in the 95th percentile for weight and had an average hip width of 17.1 inches. By 2000, women in the 95th percentile weighed 27 pounds more (226 pounds) and their hip width grew 2.6 inches. During that same period, 95th-percentile females grew an inch taller. A man in 1962 weighing 217 pounds ranked in the 95th percentile for weight and had an average hip width of 15.9 inches. By 2000, men in the 95th percentile were 27 pounds heavier (244 pounds) and their hip width grew 1.3 inches. During that same period, 95th-percentile males grew 1.2 inches taller.

In an effort to deal with this wider spread, Ford Motor Company has developed an industry-first set of nine human computer-aided design (CAD) virtual mannequins aimed at representing the population's more extreme body dimensions. The company is using the CAD models to ensure its vehicles meet customer wants, such as unprecedented amounts of storage space in front-seat consoles, while accommodating the greatest range of body types.

"Our customer population is changing," said Lucy K. White, a Ford ergonomics researcher. "But with virtual mannequins, and not cyber stick figures, we're able to properly represent our physically diverse customer base -- from petite to plus-size -- and better size up vehicle interiors to fit their needs."

The statistics and the bases for the nine virtual models are from the U.S. government.  Every decade, starting in the 1960s, government researchers gather basic data about its citizens -- including height, weight and a few other body dimensions. In 2000, the Civilian American and European Surface Anthropometry Resource (CAESAR), a U.S. Air Force project supported by Ford, clothing, and other transportation companies, measured nearly 5,000 Americans and Europeans and scanned them from head to toe, both sitting and standing.

Ford used the data to create human CAD models, or virtual mannequins, some of which represent male and female models with a high body mass index (a measurement that takes into account a person's age and weight), wide hips and shoulders, long legs, short legs, long arms, short arms and several combinations. These mannequins can be positioned in and around vehicles in various postures to examine their interaction with the environment.
 
Gary Rupp, a Ford ergonomics research engineer, says the study of human body types is nothing new, but the more recent ability to manipulate such data three-dimensionally has opened up a new world for designers and engineers. For instance, Ford ergonomists used the virtual mannequins to evaluate the cabin of the all-new 2007 Ford Edge, assessing its ability to comfortably accommodate a variety of body shapes and sizes.

"Because of increased obesity more of today's motorists are grappling with tighter fits around steering wheels, armrests and in seats," Rupp said. "Our goal is to leverage this technology to make our vehicles more comfortable and more ergonomically appealing for the full gamut of customers, including people of size."

It seems easier to change the dimensions of our cars than the dimensions of our neighbors.

Long a student of the automobile industry and the human condition, Driving Today Contributing Editor writes from his home in Villeperce, France.