Danger on the road doesn't just come from other drivers — increasingly, it's coming from the road itself.
A study by Steven Stein, litter analyst for Maryland waste-consulting firm R.W. Beck, found that debris on the road was increasingly causing obstacles for drivers.
Stein and his colleagues found that on any one-mile stretch of road in Tennessee, 70 percent of debris was unintentional litter. They discovered more than 1,200 pieces of paper and plastic, 456 truck and car parts, and 109 pieces of construction debris.
Litter on roads across the country can cause accidents, some of them deadly. Driving on a Utah interstate, Brenda Shaw didn't see an eight-foot piece of pipe on the road until it slammed through her windshield and impaled her, piercing her face and neck.
"I looked down and my hands were still moving, and I'm talking, and my legs are moving, and this gentleman is telling me to hold still," she said.
According to AAA, road debris causes thousands of accidents each year and is responsible for almost 100 deaths. Last week, a tire fell off a truck and killed one person near Seattle.
It's not just objects that litter the road. In San Francisco, an ostrich fell out of a truck and backed up traffic on the Golden Gate bridge for hours.
Stein said there was more trash this time of year because more people packed up and moved, and hotter road surfaces led to more tire treads separating.
He said the biggest change in the past decades was how much trash ended up on the road by accident. It costs states millions of dollars to clean up, and cost injured Utah driver Shaw much more.
"It's crazy. People really need to start thinking about what's on the road. I had never even thought about road debris and what damage it could possibly do," she said.