Traffic accidents are the ninth-leading cause of death worldwide and are expected to move to fifth place over the next 25 years. They are the leading killer of teenagers and young adults, causing more deaths among that group than AIDS. More than 90 percent of traffic fatality victims are in the developing world, and half are motorcyclists, bicyclists or pedestrians.

Those facts are the backdrop for a project launched Wednesday by the World Health Organization to reduce the huge but largely unrecognized burden of traffic deaths and injuries over the next decade.

The strategy is to create demand for safer roads, stricter laws and better driving in countries where the toll of traffic injuries is unusually high. It will provide transportation and public health agencies in those places with a tool kit of interventions — seat belt laws, lowered limits for alcohol-impaired driving, dedicated bike lanes, license restrictions for teenagers, improved ambulance service — that have proved lifesaving elsewhere.

“Road safety is coming out of the shadows today, and it is time,” said Etienne Krug, head of the injury prevention department at the WHO in Geneva, who was in Mexico on Wednesday to help launch the program there. About 120 countries had events for the “Decade of Action for Road Safety,” and in half of those, the head of government was involved.

“Historically there has never been much international attention on this, and we have never had that level of attention from high government officials,” Krug said.

Traffic fatality rates vary widely around the world. In northern Europe, there are eight traffic deaths per 100,000 people, which is roughly half the global rate (19 per 100,000) and one-quarter the rate in Africa (32 per 100,000).

In all, road crashes kill 1.3 million people a year — fewer than the number dying from lung cancer but more than those dying from premature birth. (In general, epidemiologists frown on the word “accidents” because, they say, it suggests that the events are unavoidable). WHO officials estimate that 5 million deaths and 50 million injuries can be prevented over the next 10 years if governments pay attention to the problem.

They cite the experience of places such as France, where the number of road deaths fell from 16,000 a year in the early 1970s to about 4,000 a year now as a consequence of steps including campaigns against drunken driving and the liberal use of speed cameras.

Many developing countries have already made big improvements, according to WHO data. In Malaysia, the installation of a motorcycle lane on a major highway reduced crashes on the stretch by 39 percent. Vietnam passed a motorcycle helmet law in 2007; within a year, hospitals reported a 16 percent drop in head injuries.

The United States is part of the global campaign. The reduction of traffic fatalities is one of the “winnable battles” recently targeted by the Centers for Disease Control and Prevention. The U.S. fatality rate per vehicle miles traveled is twice that of the lowest European countries, Thomas R. Frieden, the CDC’s director, said Wednesday during a visit to Washington to push road safety. He noted that there is a five-fold difference in traffic fatality rates among the states, with the District having the lowest (4.8 deaths per 100,000 people) and Wyoming the highest (24.6 per 100,000).

“The West does poorly. Rural areas do poorly. Speed kills,” he said.

The CDC and the Bloomberg Philanthropies, which is funded by the fortune of New York Mayor Michael R. Bloomberg (I), helped the WHO prepare the “Decade of Action” plan. Bloomberg is also providing $125 million over the next five years to help underwrite the program in 10 countries, including Brazil, India, Mexico and Russia.