WASHINGTON - On a sharp descent in the Tibetan mountains, Mian Chin knew she was in trouble when the brakes failed on her tour bus and she heard the driver declare in Mandarin Chinese, "We are going to die."

The bus, with 25 people aboard in August, was picking up speed as it headed down the hill, barreling toward a 90-degree turn in the road more than a quarter-mile away.

"I thought, 'Are we going to die like that?' " said Chin, 52, an atmospheric scientist from a Washington suburb.

But a herd of yaks happened to be crossing the road at the time. The bus slammed into more than a dozen of them, which slowed the bus before it hit a retention wall. Beyond the unfortunate yaks, there were no serious injuries. Chin was treated for minor cuts and bruises.

She considers herself incredibly lucky. But data released this week highlight the perils of traffic safety for U.S. travelers abroad. Traffic crashes are the most common cause of non-natural deaths for American tourists, according to State Department figures - more prominent than homicides, acts of terrorism, or natural disasters.

Traffic crashes caused the deaths of 741 U.S. citizens traveling overseas from 2004 to 2006, or about one-third of the 2,364 deaths, according to an analysis of State Department data by the Make Roads Safe Campaign, a nonprofit group funded by a charitable foundation in the United Kingdom dedicated to reducing global traffic deaths and injuries.

The group said the figures could be understated because some families might not report the deaths to the State Department, or some travelers might return for medical treatment and die in the United States. The report was issued yesterday as part of the first United Nations Global Road Safety Week.

Auto use has expanded rapidly in many parts of the world where transportation was once confined to bicycles. China, for example, is now the second-largest vehicle market in the world, and passenger-car sales grew 37 percent there last year.

Experts on traffic safety say many Americans overlook road-safety dangers during their vacations and need to arrive with more than just a packed suitcase, travel papers and vaccinations.

They should know about a country's road conditions, look into a travel company's safety record, avoid night travel, and follow safety standards such as buckling up and not drinking and driving.

Young adults can be particularly vulnerable. The World Health Organization reported last week that nearly 400,000 people under 25 are killed in traffic crashes annually and that car crashes were the leading cause of death worldwide for people 10 to 24.