Federal Highway Research Institute Evaluation of the Tactile Detection Response Task (TDRT) in a laboratory test using a surrogate driving set-up Roland Schindhelm and Eike Schmidt

Outline 1.Characteristics of the TDRT method 2.Background, research questions 3.Method, experimental design 4.Results 5.Conclusions European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt2

Characteristics of the TDRT TDRT is a method developed for the evaluation of information and control systems HMI (Engström et al., 2005). TDRT measures effects of secondary task load on driver attention. Main characteristics of the TDRT: Stimuli-response task Tactile stimuli presented by a vibrator fixed to the participants shoulder Stimulus duration 1 s, every 3 – 5 s Manual response by pressing a finger button European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt3

Background 1 tactile mode (TDRT) and 2 visual modes are included in the DRT method. Standardization of DRT method in progress (ISO/CD 17488). BASt is involved in coordinated international studies which aim at supporting the ISO Task Force in developing the DRT standard. Main research questions are related to –the use of DRT in different driving set-ups –difference in results obtained with the three DRT modes –sensitivity and specifity of the DRT modes European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt4

Research questions of the BASt study The BASt DRT study focuses on the Tactile DRT (TDRT). To what extent is the TDRT sensitive to systematic manipulation of task load for different types of tasks? How does the TDRT affect secondary task and primary task performance? Selection of Research questions from presentations given by Engström and Young, Yokohama Meeting 2012 European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt5

Method of the BASt study Laboratory test performed in July/August 2013 Subjects: 10 female, 12 male, age (M=41.7), licensed drivers Single-task and multiple-task scenarios derived from selected combinations of the following independent factors: –Type of primary task (visual, auditory tracking) –Type of secondary task (N-back Task, SuRT) –Task difficulty (easy, hard) –Use of TDRT (without, with) Within-subject design Order of task scenarios was counter-balanced across subjects Duration per trial: 60 sec. European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt6

Tasks, independent variables Driving task surrogate as a primary task: Continuous Tracking Task (semi-static) Manual control of the cursor via steering wheel 2 modalities of feeding back tracking deviation (visual, auditory) 2 difficulty levels (easy, hard) Easy Hard European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt7

Tasks, independent variables Secondary tasks: SuRT Visual search; manual control of the cursor via key pad 2 difficulty levels (easy, hard) N-Back task Auditory stimuli; cognitive processing; vocal response 2 difficulty levels (easy, hard) 0-Back1-Back Easy Hard European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt8 Easy Hard

Experimental set-up European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt9

Dependent variables, indicators TDRT: –mean response time –hit rate Tracking task: –root mean square deviation N-Back task: –percentage of correct answers SuRT: –mean response time European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt10

p <.01n.s. Secondary Task easy hard easy hard N-Back SuRT Primary Task easy hard easy hard Visual Tracking Aud. Tracking TDRT Tactile DRT TDRT response time in different task scenarios European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt11

Secondary Task hard N-backSuRT Primary Task easy hard easy hard Visual Tracking Auditory Tracking Effect of TDRT on primary task performance: - Tracking deviation European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt12

Secondary TaskSuRT, hard Primary TaskVisual Tracking, easy Effect of TDRT on secondary task performance: - SuRT response time European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt13

Secondary TaskN-back ( hard ) Primary TaskVisual Tracking ( easy ) Effect of TDRT on secondary task performance: - N-back percentage of correct answers European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt14

Conclusions/1 Sensitivity in triple-task scenarios: “Primary T. + Secondary T. + TDRT”  Sensitivity of TDRT to different load levels of cognitive secondary tasks could be confirmed (N-Back easy vs. hard).  TDRT seems to be not sensitive to load levels of secondary tasks which primarily demand for visual- manual resources (SuRT easy vs. hard).  TDRT is sensitive to secondary task types which vary in type of resource demands (cognitive vs. perceptual- motor) European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt15

Conclusions/2 Sensitivity in dual-task scenarios: “Primary T.+ TDRT”  TDRT seems to be not sensitive to load levels of the surrogate driving task (bendiness of the tracking path).  TDRT is sensitive to primary task types which vary in cognitive resource demands (auditory-cognitive-motor vs. visual-motor demands of tracking task). European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt16

Conclusions/3 Intrusiveness:  There are indications of the TDRT’s intrusiveness on primary task performance (tracking deviation).  No clear picture for intrusiveness of TDRT on secondary task performance. Intrusiveness of TDRT seems to depend on type of secondary task:  No intrusion on N-Back performance  Intrusion on SuRT performance European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt17

Conclusions/4 Further research recommended:  Interference between TDRT and secondary/primary task due to motor task demands.  Intrusiveness of TDRT on primary task and secondary task performance:  Comparative studies on degraded vs. normal task performance.  Limitations of applicability of TDRT (e.g. in on-road tests).  Sensitivity of TDRT to load levels of other secondary task types (generic tasks; real tasks) European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt18

Federal Highway Research Institute Thank you for your attention! European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt19

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p <.01n.s. European Conference on Human Centred Design for ITS, June 2014, ViennaSchindhelm/Schmidt21 TDRT hit rate in different task scenarios Secondary Task easy hard easy hard N-Back SuRT Primary Task easy hard easy hard Visual Tracking Aud. Tracking TDRT Tactile DRT