What we don't know.(Special Report - rebuilt autos)(insurance data)(Cover Story)

The Highway Loss Data Institute (HLDI) and its affiliate, the Insurance Institute for Highway Safety (IIHS), describe their mission as "finding out what works and what doesn't work to prevent motor-vehicle crashes in the first place." Their aim is to reduce human and property losses from automobile accidents. The combined $14.6 million annual budget of these private nonprofit groups is provided mainly by 75 insurance companies.

Through crash testing and research of damage claims make-by-make, model-by-model, the institutes analyze the human, vehicular, and environmental factors associated with accidents. CONSUMER REPORTS uses IIHS data in our safety assessments of specific models.

A unique database maintained by the institutes-millions of records on loss claims related to roughly two-thirds of all insured late-model cars and trucks in the U.S.-allows them to glean rich information about those models that are more frequently involved in accidents.

That same database could help answer critical questions about rebuilt wrecks, such as: How many totaled vehicles have been rebuilt and put back on the road? Are there patterns or trends that merit further investigation or better regulation?

There's no evidence that the safety of rebuilt vehicles is a major problem, says Brian O'Neill, president of HLDI and IIHS. "Is it possible that repairs are related to vehicle performance during a crash? That's impossible to know," he says. "If I were going to have concerns about this issue, I'd be concerned whether consumers are adequately informed about the history of the vehicle."

For this report, we asked HLDI for the vehicle-identification numbers (VINs) and other basic details for all ...