The National Safety Council (NSC) conducted a study, funded in part by Nationwide Insurance, which reviewed 180 fatal crashes from 2009 to 2011 where evidence indicated driver cell phone use. The study found that in 2011, 52% of them were not coded as involving cell phone use.

The NSC’s president and CEO Janet Froetscher said factors such as drivers not admitting cell phone use and a lack of consistency in crash reports make it difficult to determine a number that accurately reflects the number of fatal crashes that involve cell phone use.

Beyond the reasons above, NSC’s research found that in half of cases where a driver admitted cell phone use, the crash was not coded in the National Highway Traffic Safety Administration’s Fatal Analysis Reporting System. There are also an unknown number of cases where cell phone use in a fatal crash is not possible to determine, for example where a driver dies in a crash without any witnesses.

The NSC report also found major differences in cell phone use in fatal crash data as reported by states. In 2011, Tennessee reported 93 fatal crashes that involved cell phone use, but New York, which has a larger population, reported a single fatal crash where cell phone use was involved. Other examples include Texas reporting 40 but Louisiana reporting none.

NSC noted that in 2012, highway fatalities increased for the first time in seven years. NSC said that due to the risk involved with, and the prevalence of, cell phone use while driving (as reported by NHTSA and other research), the organization estimates as many as 25% of all crashes involve cell phone use.