For all the research that goes into building safer vehicles, for all the advancements that have saved untold lives and allowed many people to walk away from violent collisions, safety experts still know little about what happens inside the human body when a car hits a tree at 40 mph.

Those mysteries have driven nine of the world's largest automakers to launch an audacious plan: developing the most detailed computer model of the human body ever attempted. The results could lead to safer vehicles, designed at less expense.

The models envisioned by the Global Human Body Models Consortium would be up to 10 times more detailed than those available today — requiring a new generation of computing power — with the capability of predicting how organs and soft tissues absorb the crushing force of a car crash.

"We are changing our philosophy of designing cars for crash test dummies to designing for humans," said King Yang, a Wayne State University biomechanical engineering professor who has been working on human computer models for nearly two decades.

Researchers know how to crash cars and measure the impact, but have struggled for decades to predict how the human body's more delicate works will withstand an accident.

"What we're trying to do here is go to the next level," said J.T. Wang, group manager at General Motors Corp.'s vehicle development research lab and head of the consortium's technical committee. The model should "predict tissue-level rib fracture, aorta rupture — to try to be able to mimic and reproduce those in the computer."

The consortium was formed about a year ago, after automakers decided to pool their resources toward developing a single model. In addition to the automakers — GM, Ford, Toyota, DaimlerChrysler, Honda, Nissan, Renault, Hyundai and PSA Peugeot Citroen — the group includes two parts suppliers, TRW and Takata.

All have pledged a total of $18 million to develop by 2011 the first set of six models — three men, three women, with small, average and large sizes for each gender. After the first round, the project envisions spending several years to build a family of virtual humans, from children to grandparents, in all sizes.

Saeed Barbat, manager of Ford Motor Co.'s passive safety research and advanced engineering, said the human models could be used to set new safety standards and solve problems such as low-speed crashes that cause brain damage or injuries to the smallest passengers.

"A lot of children's injuries can't be predicted by any dummy," Barbat said. "A model like this might be able to give you that information."

Better technology has saved thousands of lives in car crashes during the past 20 years, as the rate of fatalities and injuries has fallen even as roads have grown more crowded. But U.S. deaths from traffic accidents have been stuck for years at just under 40,000 annually, and the death rate per miles traveled rose in 2005 for the first time since 1986.

Auto-safety experts use a mix of tools today to measure and improve crashworthiness, including dummies, computer models and cadavers. Automakers routinely use exact computer models of their vehicles and parts to run hundreds of virtual tests, making small changes later verified with actual crash tests.

Those tests can measure precisely the forces that ripple across a driver's body in a crash, predicting whether major bones will break. Those data determine a vehicle's grade on the U.S. government's five-star rating system for safety.

But a human body has far more complex parts than a car, and today's models offer only estimates.