The trend may reflect efforts by the federal Centers for Disease Control and Prevention and other groups to get Hollywood to convey positive public health messages. But the study also shows these efforts haven't been universally endorsed.
For example, actor Will Ferrell in the 2003 Christmas movie "Elf" gets knocked down by a New York City taxi while crossing the street. He bounces back up without a scratch - but at least he was walking in a crosswalk.
Still, the study's lead author, CDC researcher Jon Eric Tongren, said the scene minimizes the accident's dangers and may give young children a false sense of safety.
And in the 2005 comedy "Yours, Mine and Ours," about a family with 18 kids, the children are wearing life jackets during a boat trip - but not the parents.
The two films were among 67 popular movies from 2003 to 2007 examined in the study. The movies were rated G for general audiences or PG - parental guidance suggested. Results were compared with two previous CDC studies, and were published Monday in Pediatrics.
Among the findings, compared with the studies from 1998-2002 and 1995-97:
-56 percent of car passengers wore seat belts, versus 35 percent and 27 percent
-35 percent of characters used crosswalks, versus 15 percent and 16 percent
-25 percent of bicyclists wore helmets, versus 15 percent and 6 percent
-75 percent of boaters wore life jackets, versus none and 17 percent
Some unsafe behavior increased, including riding motorcycles without a helmet.
Joan Graves, ratings chief at the Motion Picture Association of America, said movies tend to reflect what's going in real life. She cited widespread seat belt laws, helmet use, and awareness about dangers of drunken driving as cultural trends that have affected movie plot lines.
The CDC and other public health groups have urged film and TV producers to convey accurate and safe health messages because mass media has such a powerful influence on behavior - especially children's, Tongren said. He encourages parents to make sure their kids understand what's safe and unsafe in TV and movie action.
The University of Southern California's Hollywood, Health & Society program is one way CDC and others have reached the industry. The program links producers and writers with health experts and reference material on a variety of topics, although it doesn't pitch specific story lines, said program director Sandra Buffington.
Tongren said the entertainment industry "seems to be coming around. We would hope that they continue" to do so.