You've heard about the chicken that crossed the road. But have you heard the one about the chickens traveling down the road? It's no laughing matter. Crates of chickens being trucked along the highway in the back of an open truck can shoot a bunch of nasty bacteria into the cars behind them, researchers have found.

Drivers stuck behind such a truck should "pass them quickly," advised study co-author Ana Rule, a researcher at Johns Hopkins University.

Even so, it's not clear that germy debris will make you sick. None of the scientists who studied this problem got sick. And the disease-causing bacteria in question are normally spread by food or water, not air.

Rule and her colleagues at the Bloomberg School of Public Health focused on the so-called Delmarva Peninsula, a coastal area that includes parts of Delaware, Maryland and Virginia. The region is a chicken mecca, with one of the highest concentrations of broiler chickens per acre in the nation.

The researchers chose a 17-mile stretch of highway connecting chicken farms in Maryland to a processing plant to the south in Accomac, Va. They rode in four-door cars with all the windows down and the air conditioning off.

They checked the cars for bacteria after driving when there were no chicken trucks around. And they checked for bacteria after 10 trips behind flatbed trucks carrying crates of broiler chickens.

They collected bacteria from air samples, door handles and soda cans inside the car.

In all the truck chases, they found high levels of certain bacteria, including some that are resistant to antibiotics.

The study, released this week, is being published in the first issue of the Journal of Infection and Public Health, and it's billed as the first to look at whether poultry trucking exposes people to antibiotic-resistant bacteria.

It was a casual conversation that inspired the effort.

"Somebody said, 'I went to the beach the other day and I got stuck behind a chicken truck, and boy, is that nasty,'" Rule said.

She said studies to determine if chicken trucks can make you sick are somewhere down the road.

Dr. Keith Klugman, an Emory University epidemiologist who was not involved in the research, said getting sick that way is unlikely. Most healthy people don't suffer serious illness from these bacteria even when exposed in more conventional ways.

"It was kind of an unnatural experiment, in that people were driving behind these trucks with the windows open and the air conditioning off — for 17 miles," he added. "If you were driving behind a truck that was spewing stuff out the back of it, the first thing you would probably do is close your windows."