In a 2011 study it was reported that over 90% of college students surveyed text (initiate, reply or read) while driving. On July 27, 2009, the Virginia Tech Transportation Institute released preliminary findings of their study of driver distraction in commercial vehicles. Two studies, comprising about 200 long-haul trucks driving 3 million combined miles, used video cameras to observe the drivers and road; researchers observed "4,452 safety-critical events, which includes crashes, near-crashes, crash-relevant conflicts, and unintended lane deviations." 81% of the safety-critical events had some type of driver distraction. Text messaging had the greatest relative risk, with drivers being 23 times more likely to experience a safety-critical event when texting. The study also found that drivers typically take their eyes off the forward roadway for an average of four out of six seconds when texting, and an average of 4.6 out of the six seconds surrounding safety-critical events.