active and passive fatigue in simulated driving dyani j. saxby

Active and Passive Active and Passive Fatigue in Simulated Fatigue in Simulated

DrivingDriving

Dyani J. Saxby

Study SynopsisStudy Synopsis

►Development of more automated Development of more automated vehicle systems might remove some of vehicle systems might remove some of the task load that can lead to fatigue ?the task load that can lead to fatigue ?

►Active fatigue may stem from active Active fatigue may stem from active physical control of vehicle system, physical control of vehicle system, while passive fatigue may stem from while passive fatigue may stem from the driver taking on a supervisory role the driver taking on a supervisory role (Desmond & Hancock, 2001). (Desmond & Hancock, 2001).

Our Current Understanding Our Current Understanding of Fatigueof Fatigue

► FatigueFatigue - fatigue itself is multifaceted and - fatigue itself is multifaceted and difficult to define precisely (Desmond & difficult to define precisely (Desmond & Hancock, 2001) .Hancock, 2001) .

► Causes of FatigueCauses of Fatigue - It is often difficult to separate task-induced - It is often difficult to separate task-induced

fatigue from sleep loss and circadian rhythm fatigue from sleep loss and circadian rhythm effects, which often interact in real-world effects, which often interact in real-world driving scenarios.driving scenarios.

- The manifestation of symptoms is dependent - The manifestation of symptoms is dependent upon a number of factors, including individual upon a number of factors, including individual differences in personality and coping, as well differences in personality and coping, as well as the task itself (Hitchcock & Matthews, as the task itself (Hitchcock & Matthews, 2005) .2005) .

►wide range of symptoms wide range of symptoms

- ‘mental’ symptoms (e.g. boredom, - ‘mental’ symptoms (e.g. boredom, loss of alertness )loss of alertness )

- ‘physical’ symptoms (e.g. muscle - ‘physical’ symptoms (e.g. muscle pain, eyestrain) pain, eyestrain)

- changes in brain function - changes in brain function

Measures of FatigueMeasures of Fatigue

Types of MeasuresTypes of Measures It is important to distinguish between It is important to distinguish between

mental and physical symptoms and the mental and physical symptoms and the effects on performance that may result. effects on performance that may result.

It is critical to obtain both subjective It is critical to obtain both subjective state and objective performance state and objective performance measures when researching driver fatigue measures when researching driver fatigue (Craig & Cooper, 1992). (Craig & Cooper, 1992).

Types of MeasuresTypes of Measures

►Performance MeasuresPerformance Measures Used to assess driver fatigue on a driving Used to assess driver fatigue on a driving

simulator : curvature error, heading error, simulator : curvature error, heading error, steering wheel rate, lane deviation, steering wheel rate, lane deviation, reaction time, traffic violations, and reaction time, traffic violations, and divided attention tasks divided attention tasks

Performance MeasuresPerformance Measures

► LimitationsLimitations variety of individual differences : more variety of individual differences : more

experienced driver’s increased capacity to cope experienced driver’s increased capacity to cope with fatigue and compensate accordingly with fatigue and compensate accordingly

performance indices may be affected by factors performance indices may be affected by factors other than fatigue : distraction and stress other than fatigue : distraction and stress

► Subjective measures of fatigue that are Subjective measures of fatigue that are independent of performance measures independent of performance measures are useful to gain a full understanding are useful to gain a full understanding of driver fatigue, and to establish that of driver fatigue, and to establish that the fatigue state is linked to loss of the fatigue state is linked to loss of performance and safety.performance and safety.

Traits and Subjective Traits and Subjective StateState

►Traits are stable aspects of personality Traits are stable aspects of personality that predispose individuals toward that predispose individuals toward reacting to various situations in a reacting to various situations in a certain manner. certain manner. research suggests that personality research suggests that personality

measures that are measures that are specificspecific to driving are to driving are better predictors of performance because better predictors of performance because individuals may actually have a personality individuals may actually have a personality that is unique to the driving experience. that is unique to the driving experience.


► States are considered to be temporary reStates are considered to be temporary reactions to a situation (Matthews, et al., 20actions to a situation (Matthews, et al., 2000). 00). State measures have a more direct impact on State measures have a more direct impact on

performance. Unfortunately, state models are performance. Unfortunately, state models are less advanced. less advanced.


►Fatigue may overlap considerably with otFatigue may overlap considerably with other states such as stress. her states such as stress.

►Different task demands or situational factDifferent task demands or situational factors can impact subjective fatigue states in ors can impact subjective fatigue states in unique ways. unique ways.


►Matthews’ (2002) transactional model Matthews’ (2002) transactional model of driver stress and fatigue suggests of driver stress and fatigue suggests that individual personality factors that individual personality factors interact with situational demands, interact with situational demands, which in turn, elicit cognitive processes which in turn, elicit cognitive processes that can reduce or exacerbate the that can reduce or exacerbate the effects that driver stress vulnerability effects that driver stress vulnerability has on subjective states. has on subjective states.

Fatigue Models for Fatigue Models for PerformancePerformance

►Unidimensional Fatigue ModelsUnidimensional Fatigue Models De Vries, Michielsen, and Van Heck (2003).De Vries, Michielsen, and Van Heck (2003).

►They administered six questionnaires by mail to 35They administered six questionnaires by mail to 351 individuals who worked at least 20 hours per wee1 individuals who worked at least 20 hours per week.k.

► All six questionnaires were found to have a one-faAll six questionnaires were found to have a one-factor solution as revealed by exploratory factor anactor solution as revealed by exploratory factor analyses. Furthermore, analysis of the pooled questiolyses. Furthermore, analysis of the pooled questions showed that a one-factor solution, which accouns showed that a one-factor solution, which accounted for 44 percent of the total variance, was most nted for 44 percent of the total variance, was most appropriate. appropriate.


►Multidimensional ModelsMultidimensional Models - Many researc - Many researchers have rejected the notion that fatigue hers have rejected the notion that fatigue is aunidimensional construct and have insis aunidimensional construct and have instead found evidence supporting a multiditead found evidence supporting a multidimensional approach. mensional approach.


►Multidimensional ModelsMultidimensional Models Smetz, Garssen, Bonke, and Haes (1995) : testSmetz, Garssen, Bonke, and Haes (1995) : test

ed the psychometric properties of the Multidied the psychometric properties of the Multidimensional Fatigue Inventory (MFI) on a broad mensional Fatigue Inventory (MFI) on a broad sample of individuals sample of individuals


►Multidimensional ModelsMultidimensional Models American Cancer Society Behavioral Research American Cancer Society Behavioral Research

Center : Center : ►Confirmatory factor analyses revealed five factors: Confirmatory factor analyses revealed five factors:

General Fatigue, Emotional Fatigue, Physical General Fatigue, Emotional Fatigue, Physical Fatigue, Mental Fatigue, and Vigor. Fatigue, Mental Fatigue, and Vigor. LavidorLavidor

Weller and Babkoff (2002) : Weller and Babkoff (2002) : ►found evidence that fatigue is multidimensional in found evidence that fatigue is multidimensional in

nature in non-patient populations as well. nature in non-patient populations as well. ► the highest correlations between Mental and Physthe highest correlations between Mental and Phys

ical fatigue and between Severity and Tiredness.ical fatigue and between Severity and Tiredness.


►Unidimensional Fatigue Models Unidimensional Fatigue Models v.s. v.s. Multidimensional ModelsMultidimensional Models To summarize, there is currently no “gold stTo summarize, there is currently no “gold st

andard” for the assessment of fatigue. andard” for the assessment of fatigue. It is possible that some of the disagreement aIt is possible that some of the disagreement a

mongst researchers regarding both approachmongst researchers regarding both approaches may be due to psychometric issues.es may be due to psychometric issues.


►Psychometric IssuePsychometric Issue One reason for lack of consensus amongst resOne reason for lack of consensus amongst res

earchers is that the appropriateness of unidiearchers is that the appropriateness of unidimensional versus multidimensional measures mensional versus multidimensional measures might be context dependent. might be context dependent.


►Hitchcock and Matthews (2005) Hitchcock and Matthews (2005) have identified several psychometric issues, whave identified several psychometric issues, w

hich may contribute to the research discrepanhich may contribute to the research discrepancies concerning the dimensionality of fatigue. cies concerning the dimensionality of fatigue. ► the the rangerange of constructs sampled on various fatigu of constructs sampled on various fatigu

e instruments is highly variablee instruments is highly variable►hierarchical models might be useful, but little attehierarchical models might be useful, but little atte

ntion has been allocated to them in fatigue assessntion has been allocated to them in fatigue assessment. For example : WAIS – IIIment. For example : WAIS – III


►Dundee Stress State QuestionnaireDundee Stress State Questionnaire assess transient states associated with stress, assess transient states associated with stress,

arousal, and fatigue, and to reflect the multidiarousal, and fatigue, and to reflect the multidimensionality of these statesmensionality of these states

Automation and FatigueAutomation and Fatigue

►A Remedy for Driver Fatigue?A Remedy for Driver Fatigue? Automobile manufacturers often promote incAutomobile manufacturers often promote inc

reased automation as a way of increasing safereased automation as a way of increasing safety (Funke, Matthews, Warm, & Emo, 2007). ty (Funke, Matthews, Warm, & Emo, 2007).

►Reducing workload may not always be an Reducing workload may not always be an ideal goal ideal goal When operators are in underload or overload When operators are in underload or overload

conditions they may not be able or willing to aconditions they may not be able or willing to allocate efforts toward the task; as a result, perllocate efforts toward the task; as a result, performance may be compromised. formance may be compromised.

Automation and FatigueAutomation and Fatigue

►Recent Advancements in Recent Advancements in Automated Vehicle SystemsAutomated Vehicle Systems Intelligent Parking Assist systems Intelligent Parking Assist systems

►help drivers parallel park help drivers parallel park ► “ “Car, Park Thyself,” the reporter warned, Car, Park Thyself,” the reporter warned,

“Hands-free driving doesn't mean you can “Hands-free driving doesn't mean you can read a book or doze off. read a book or doze off.

• Recent Advancements in Automated Recent Advancements in Automated Vehicle SystemsVehicle Systems

Adaptive Cruise Control (ACC) Adaptive Cruise Control (ACC) ►It has the ability to maintain a set speed. In It has the ability to maintain a set speed. In

addition to maintaining a set speed, it also has addition to maintaining a set speed, it also has sensors that are able to detect vehicles in sensors that are able to detect vehicles in front of the driver and adjust speed front of the driver and adjust speed accordingly accordingly

►ACC does reduce mental workload, but only in ACC does reduce mental workload, but only in limited circumstances (Young & Stanton, limited circumstances (Young & Stanton, 2004).2004).

Active versus Passive Active versus Passive FatigueFatigue

►Passive fatigue may result from the driver Passive fatigue may result from the driver taking on a supervisory role.taking on a supervisory role.

►Active fatigue may correspond to overloaActive fatigue may correspond to overload conditions, whereas passive fatigue may d conditions, whereas passive fatigue may correspond to underload conditions. correspond to underload conditions.

Active versus Passive Active versus Passive FatigueFatigue

► Automation of vehicle systems will exposAutomation of vehicle systems will expose drivers to a new supervisory role, which e drivers to a new supervisory role, which reduces active control, producing passive reduces active control, producing passive fatigue, associated with monotony and bofatigue, associated with monotony and boredom. redom.

► It is important to test whether active and It is important to test whether active and passive fatigue states are genuinely differpassive fatigue states are genuinely different, perhaps having different implications ent, perhaps having different implications for driver behavior and safety. for driver behavior and safety.

►Drive DurationDrive Duration

►Fatigue Manipulations on the Driving SiFatigue Manipulations on the Driving Simulatormulator

►Specific HypothesesSpecific Hypotheses

active and passive fatigue in simulated driving dyani j. saxby

Documents

fatigue state

active fatigue

passive fatigue

subjective state fatigue

taskinduced fatigue

state measures

personality measures

loss of performance