Messages beyond the phone: Processing variable message signs while attending hands-free phone calls.

Area of Science:

• Cognitive Psychology
• Human Factors Engineering
• Traffic Safety

Background:

• Hands-free phone use is prevalent, yet its impact on driving, particularly on processing critical traffic information, requires further investigation.
• Variable Message Signs (VMS) are crucial for conveying real-time traffic information, but driver distraction may impede their effectiveness.

Purpose of the Study:

• To investigate the effects of different types of cognitive distraction from hands-free phone conversations on VMS information processing.
• To assess the impact of cognitive distraction on driving performance and physiological measures of mental effort (heart rate).

Main Methods:

• Participants completed a driving simulation task responding to VMS messages under three conditions: no distraction, visuospatial distraction, and conceptual distraction.
• Driving performance (response accuracy, variability in distance) and heart rate were measured.

Main Results:

• Visuospatial distraction from phone calls led to significantly more errors in responding to VMS messages.
• Both visuospatial and conceptual distractions increased response distance variability and heart rate, indicating higher cognitive effort.
• Distraction did not significantly affect vehicle speed control or lateral positioning.

Conclusions:

• Hands-free phone conversations impose cognitive costs, impairing the processing of VMS information and increasing mental workload for drivers.
• The impact of distraction varies across driving subtasks, with VMS processing being more susceptible than speed or lane control.
• Findings support policy discussions on hands-free phone use and emphasize the need for technological solutions to mitigate risks associated with missed VMS information.