Speed maintenance under cognitive load - Implications for theories of driver behaviour

Area of Science:

• Traffic Psychology
• Driver Behavior Analysis
• Human Factors in Transportation

Background:

• Existing driver behavior theories lack widespread acceptance due to testing difficulties.
• Motivational theories of driving behavior are divided into two groups: constant monitoring of subjective variables (e.g., risk) versus variables becoming relevant only after a threshold is passed.
• Understanding these motivational thresholds is crucial for developing effective traffic safety interventions.

Purpose of the Study:

• To investigate whether subjective driving variables like risk and effort are constantly monitored or only become relevant above a certain speed threshold.
• To examine the influence of cognitive load on driver responses to speed manipulations.
• To differentiate between two prominent classes of motivational theories in driver behavior.

Main Methods:

• Utilized a driving simulator to manipulate participant speeds (±10, 20, 30 km/h from preferred speed) and cognitive load (mental arithmetic task).
• Collected verbal ratings on task difficulty, effort, feeling of risk, and speed typicality after each speed interval.
• Repeated speed manipulations and data collection across seven different speed change conditions.

Main Results:

• A threshold effect was observed for task difficulty, effort, and feeling of risk; significant increases were noted only after speeds exceeded participants' preferred travel speeds.
• This threshold relationship persisted even when participants were under cognitive load, although the effect was diminished.
• Drivers experienced difficulty maintaining speeds below their preferred level when under cognitive load, but found exceeding preferred speeds easier to maintain in the short term.

Conclusions:

• Findings support the motivational theory that subjective variables like risk are relevant only after a certain threshold is passed, rather than being constantly monitored.
• Cognitive load impacts driver's ability to manage speed relative to their preference, making lower-than-preferred speeds more challenging.
• The study provides empirical evidence for threshold-based models of driver motivation and behavior, informing future traffic psychology research and safety strategies.