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May 29, 2013

Recently released results from a new Virginia Tech Transportation Institute (VTTI) naturalistic driving study continue to show that distracted driving is a tangible threat.

The study, entitled The Impact of Hand-Held and Hands-Free Cell Phone Use on Driving Performance and Safety Critical Event Risk, shows that engaging in visual-manual subtasks (such as reaching for a phone, dialing and texting) associated with the use of hand-held phones and other portable devices increased the risk of getting into a crash by three times. The data were collected by VTTI and Westat. The study, which was conducted under a separate contract from the National Highway Traffic Safety Administration (NHTSA), found:

  • Text messaging, browsing and dialing resulted in the longest duration of drivers taking their eyes off the road.
  • Text messaging increased the risk of a crash or near-crash by two times and resulted in drivers taking their eyes off the road for an average of 23 seconds total.
  • Activities performed when completing a phone call (reaching for a phone, looking up a contact and dialing the number) increased crash risk by three times.
  • There is no direct increased crash risk from the specific act of talking on a cell phone. However, visual-manual tasks (locating the phone, looking at the phone and touching the phone) are always involved when using a hand-held cell phone. This makes the overall use of a hand-held cell phone riskier when driving.
  • Even portable hands-free and vehicle-integrated hands-free cell phone use involved visual-manual tasks at least half of the time, which is associated with a greater crash risk.

Additional details of safety-critical event risks related to cell phone use are included in the following table. To learn more about the VTTI study, view the full report here.

Safety-critical Event Risk Associated with Cell Phone Use

Rate Ratio
95% Confidence Interval*
Overall Cell Phone Use 1.32 0.96 – 1.81
Visual-manual Subtask (such as looking at or touching a cell phone, reaching for the phone, dialing, texting, etc.) 2.93** 1.90­­ – 4.51

Call-related Visual-manual Subtask

3.34** 1.76 – 6.35

Text-related Visual-manual Subtask

2.12** 1.14 – 3.96


0.84 0.55 – 1.29

Talking/Listening (Hand-held Phone)

0.84 0.47 – 1.53

Talking/Listening (Portable Hands-free, such as a Bluetooth earpiece)

1.19 0.55 – 2.57

Talking/Listening (Integrated Hands-free, which is built into the vehicle navigation system)

0.61 0.27 – 1.41
Hand-held Cell Phone Use 1.73** 1.20­­ – 2.49
Portable Hands-free Cell Phone Use 1.06 0.49 – 2.30
Integrated Hands-free Cell Phone Use 0.57 0.25 – 1.31

* Indicates 95% confidence that the actual safety-critical event risk falls within the lower and upper limits

** Indicates a difference at the .05 level of significance

Source: Fitch, G. A., Soccolich, S. A., Guo, F., McClafferty, J., Fang, Y., Olson, R. L., Perez, M. A., Hanowski, R. J., Hankey, J. M., & Dingus, T. A. (2013, April). The impact of hand-held and hands-free cell phone use on driving performance and safety-critical event risk. (Report No. DOT HS 811 757). Washington, DC: National Highway Traffic Safety Administration

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