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Cognitive load and detection thresholds in car following situations: safety implications for using mobile (cellular) telephones while driving.

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Lamble D, Kauranen T, Laakso M, Summala H · 1999

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Mobile phone conversations impair driving reaction times by 0.5 seconds regardless of whether phones are handheld or hands-free.

Plain English Summary

Summary written for general audiences

Researchers tested 19 drivers on a real highway to see how mobile phone use affects their ability to react when the car ahead brakes. They found that both hands-free phone conversations and manual dialing delayed drivers' brake reaction times by about 0.5 seconds and reduced their collision avoidance time by nearly 1 second. This demonstrates that hands-free phone options don't eliminate the safety risks of mobile phone use while driving.

Why This Matters

This 1999 study provides crucial evidence that the cognitive demands of mobile phone use, not just the physical handling of devices, create dangerous driving impairments. The researchers found that mental tasks like phone conversations produced reaction delays nearly identical to visual distractions like dialing numbers. What makes this research particularly significant is that it directly challenges the widespread belief that hands-free phone use is safe while driving. The reality is that your brain's capacity for attention is limited, and phone conversations compete with driving for these critical cognitive resources. At highway speeds, a half-second delay in braking can mean the difference between stopping safely and a rear-end collision.

Exposure Information

Specific exposure levels were not quantified in this study.

Study Details

This study was aimed at investigating drivers' ability to detect a car ahead decelerating, while doing mobile phone related tasks.

Nineteen participants aged between 20 and 29 years, (2000-125000 km driving experience) drove at 80 ...

The results indicated that drivers' detection ability was impaired by about 0.5 s in terms of brake ...

It was concluded that neither a hands-free option nor a voice controlled interface removes the safety problems associated with the use of mobile phones in a car.

Cite This Study
Lamble D, Kauranen T, Laakso M, Summala H (1999). Cognitive load and detection thresholds in car following situations: safety implications for using mobile (cellular) telephones while driving. Accid Anal Pre 31(6):617-623, 1999.
Show BibTeX
@article{d_1999_cognitive_load_and_detection_2334,
  author = {Lamble D and Kauranen T and Laakso M and Summala H},
  title = {Cognitive load and detection thresholds in car following situations: safety implications for using mobile (cellular) telephones while driving.},
  year = {1999},
  
  url = {https://pubmed.ncbi.nlm.nih.gov/10487336/},
}
PubMed: 10487336

Cited By (468 papers)

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Quick Questions About This Study

No, hands-free phone use does not eliminate driving safety risks. A 1999 highway study found that hands-free conversations delayed brake reaction times by 0.5 seconds, just like manual dialing. Both methods reduced collision avoidance time by nearly one full second.
Phone conversations while driving delay brake reaction time by approximately 0.5 seconds according to real-world highway testing. This delay occurs whether using hands-free devices or manually dialing, creating significant safety risks during emergency braking situations.
Voice controlled phone interfaces do not make driving safer. Research testing 19 drivers on actual highways demonstrated that voice control creates the same cognitive impairment as manual dialing, delaying reaction times and reducing collision avoidance ability.
Mobile phone use while driving reduces time-to-collision by almost one full second. This dramatic reduction in available reaction time occurs regardless of whether drivers use hands-free options or manually operate their phones during conversations.
Yes, cognitive load from phone calls significantly impairs highway driving performance. Real-world testing showed that the mental effort required for phone conversations creates detection delays similar to visually dividing attention between road and phone keypad.