The fact that mobile phones can be distracting to drivers is probably not a newsflash to most of us, whether we're the perpetrators or the observers. Although the need for an academic study quantifying the extent of distraction may seem redundant, driver distraction is a major issue of discussion with safety regulators, the insurance industry, and automotive designers. The New England Journal of Medicine just released a study identifying the major sources of distraction in a car, as well as a comparative analysis of distraction between novice and more experienced drivers.
Unsurprisingly, the novice drivers were much more likely to become distracted by use of mobile phones in the car, on average three to five times more likely to be involved in a crash or near-crash through dialing or reaching for a phone. However, the data is not exactly representative of the current ubiquity of smartphones, with the two components of the study being conducted from June 2006 through September 2008, and the other from January 2003 through July 2004. The Apple iPhone was released to the public in June 2007. Built-in Bluetooth hands-free connectivity and dialing also did not start to become common in cars until mid-decade, two advancements that could have a bearing on driver distraction, both positive and negative.
If you want to take a deep dive into the methodology and statistics in the study, you can check out the study at this link.