According to statistics released by the U.S. Department of Transportation on Monday, 5,474 people were killed in distracted driving–related crashes in 2009, and another 448,000 were injured on U.S.highways.

Transportation Secretary Ray LaHood cautioned that the actual number of distracted driving accidents is likely much higher. LaHood said in an interview that many states don’t consistently document whether or not distracted driving was a factor in crashes, which makes it impossible to know the true extent of the problem.

A recent study by the National Highway Traffic Safety Administration revealed that deaths in distracted driving–related crashes actually increased from 10% to 16% from 2005 to 2009, despite the fact that overall traffic fatalities in 2009 were at a 60 year low