Roland Schindhelm and Eike Schmidt

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/Schmidt 2

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


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


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


Method of the BASt study

Laboratory test performed in July/August 2013• Subjects: 10 female, 12 male, age 19-64 (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.


Tasks, independent variables

• Driving task surrogate as a primary task:

Continuous Tracking Task (semi-static)Manual control of the cursor viasteering wheel- 2 modalities of feeding back

tracking deviation(visual, auditory)

- 2 difficulty levels (easy, hard)

Easy Hard


Tasks, independent variables

• Secondary tasks:

SuRTVisual 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-Back 1-Back

Easy Hard


Easy Hard

Experimental set-up


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


0100200300400500600700800900

1000

Mea

n re

spon

se t

ime

(ms)

p < .01 n.s. n.s.n.s.

Secondary Task

easy hard easy hard

N-Back SuRT

Primary Task easy hard easy easy hard

Visual Tracking Aud. Tracking TDRT Tactile DRT

TDRT response time in different task scenarios


0

500

1000

1500

2000

2500

without TDRT

with TDRT

Roo

t m

ean

squa

re d

evia

tion

(p

xl)

p < .05n.s.

p < .01 p < .001

n.s.p < .05

Secondary Task hard hard N-back SuRT

Primary Task easy easy hard easy hard Visual Tracking Auditory Tracking

Effect of TDRT on primary task performance: - Tracking deviation


5

6

7

8

without TDRT

with TDRT

Mea

n re

spon

se t

ime

(s)

p < .01

Secondary Task SuRT, hardPrimary Task Visual Tracking, easy

Effect of TDRT on secondary task performance:- SuRT response time


Secondary Task N-back (hard)Primary Task Visual Tracking (easy)

Effect of TDRT on secondary task performance:- N-back percentage of correct answers

0102030405060708090

100110

without TDRTwith TDRT

Perc

enta

ge o

f co

rrec

t an

swer

s (%

)n.s.


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)


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).


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


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)


Federal Highway Research Institute

Thank you for your attention!


Schindhelm/Schmidt 20

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European Conference on Human Centred Design for ITS, June 2014, Vienna

Roland Schindhelm and Eike Schmidt

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