Distracted drivers are responsible for the deaths of a rising number of pedestrians and bicyclists, researchers at the University of Nebraska Medical Center say.

Researchers looked at data from 2005 to 2010 and found that the number of pedestrians hit and killed by distracted drivers rose from 344 to 500 during that period. The number of bicyclists killed increased from 56 to 73.

The Tampa area is one of the worst in the U.S. for traffic fatalities involving pedestrians and bicyclists. In 2012, 32 pedestrians were struck and killed by vehicles in Hillsborough County. In addition, 13 cyclists died as the result of car accidents.

Fernando Wilson, associate professor at the University of Nebraska Medical Center, said that distracted driving is difficult to address in part because it is so pervasive. “I don’t think there’s a day that I don’t see someone driving and using their cell phone, a lot of times they’re texting,” he said in a news release.

Wilson said the number of deaths related to distracted driving may be underreported because of the difficulty for law enforcement to prove that a driver was distracted at the time of an accident.

Not only are laws against distracted driving difficult to enforce, but there is not much social stigma attached to using a cellphone behind the wheel, Wilson said.

“The evidence on policies curbing distracted driving is very mixed and some research suggests policies are just not working – that we’re not really making a dent on distracted driving,” Wilson said. To better protect pedestrians and cyclists, he said, we need to consider adding marked crosswalks and bike lanes.

The study found that 65 percent of pedestrians killed by distracted drivers were white men between ages 25 and 64. They were more likely to have been hit in a city outside of a marked crosswalk.

Among bike riders who were struck and killed by distracted drivers, 83 percent were white males between the ages of 25 and 64.

“People have to be aware that this problem is not going away anytime soon,” Wilson said. “So when you’re crossing the street or cycling, you need to be cognizant about this new threat to roadway safety.”