1. Volvo Technology Humans System Integration Volvo Technology Effects of visual and cognitive load on the Lane Change Test – preliminary results Johan Engström & Gustav Markkula Volvo Technology Corporation Driver Metrics Workshop Ottawa October 2-3, 2006

2. Volvo Technology Humans System Integration Volvo Technology Background Existing results from (HASTE and other studies) show that visual and cognitive tasks have rather different effects on driving Effects of visual tasks Reduced lateral control (increased standard deviation of lane position) Reduced event detection performance (e.g. PDT) Speed/headway compensation Effects of cognitive tasks Improved lateral control (reduced variance of lane position) Gaze concentration towards road centre Reduced event detection performance No speed/headway compensation Visual and cognitive tasks both result in increased LCT normative path deviation – but could this common effect have different origins? Discussed at LCT TF meeting in Shonen Village in connection to reference tasks…

3. Volvo Technology Humans System Integration Volvo Technology Visual vs. cognitive tasks - definitions Purely visual=requires diversion of gaze from the road centre but no cognitive activity (e.g. just looking back and forth…) Purely cognitive=does not require gaze diversion (e.g. phone conversation, speech interaction etc.) In practice, most visual tasks involve a cognitive component – however, the degree of cognitive load varies (e.g. for the Arrows and Circles tasks the cognitive load could be assumed to be minimal) However, many real tasks could be regarded as purely cognitively loading

4. Volvo Technology Humans System Integration Volvo Technology Hypotheses tested Visual tasks mainly lead to reduced lateral control during the lane changes but also (to a lesser degree) to reduced detection performance Cognitive tasks mainly lead to late or erroneous detection Thus, both tasks lead to increased deviation from the normative path, but (partly) for different reasons

5. Volvo Technology Humans System Integration Volvo Technology Existing work: Mattes et al. (in AIDE D2.2.5, Östlund et al., 2005)

6. Volvo Technology Humans System Integration Volvo Technology Results, Mattes et al. (in AIDE)

7. Volvo Technology Humans System Integration Volvo Technology Method Same data as used by Mattes et al. in AIDE 30 subjects (subset of data in the study) No task priority in instructions Sign: content pop-up Secondary tasks: Cognitive easy: Count up by 2 Cognitve hard: Count down by 7 Visual easy: ”Ring detection task” – large difference between rings Visual hard: ”Ring detection task” – small difference between rings

8. Volvo Technology Humans System Integration Volvo Technology Results: First qualitative analysis, example 1 = detection/ interpretation errors = loss of control = Baseline = Cognitive (easy + hard) = Visual (easy + hard)

9. Volvo Technology Humans System Integration Volvo Technology = detection/ interpretation errors = loss of control = Baseline = Cognitive (easy + hard) = Visual (easy + hard) Results: First qualitative analysis, example 2

10. Volvo Technology Humans System Integration Volvo Technology = detection/ interpretation errors = loss of control = Baseline = Cognitive (easy + hard) = Visual (easy + hard) Results: First qualitative analysis, example 3

11. Volvo Technology Humans System Integration Volvo Technology Results: First qualitative analysis – manual classification of errors

12. Volvo Technology Humans System Integration Volvo Technology First conclusions from qualitative analysis Qualitative analysis seems to support the hypothesis: Visual task mainly leads to errors related to reduced control, but also some detection errors Cognitive task almost only lead to detection/interpretation errors But can these effects be quantified?

13. Volvo Technology Humans System Integration Volvo Technology Preliminary results of quantitative analysis

14. Volvo Technology Humans System Integration Volvo Technology Quantifying loss of control (I): Mean difference of lateral position (~mean lateral velocity) BaselineCogEasyCogHardVisEasyVisHard Baseline---0.6680.0950.000 CogEasy---0.995 CogHard--- VisEasy---1.000 VisHard---

15. Volvo Technology Humans System Integration Volvo Technology Quantifying loss of control (II): High-pass filtred standard deviation of lateral position BaselineCogEasyCogHardVisEasyVisHard Baseline---0.6870.2330.000 CogEasy---1.000--- CogHard--- VisEasy---0.790 VisHard---

16. Volvo Technology Humans System Integration Volvo Technology Towards quantifying missed detection/interpretation Fraction consistent lane selected (any single lane selected >75% of distance between two signs) BaselineCogEasyCogHardVisEasyVisHard Baseline---0.7350.0600.000 CogEasy---0.972 CogHard--- VisEasy---0.119 VisHard---

17. Volvo Technology Humans System Integration Volvo Technology Quantifying missed detection/interpretation: Fraction correct lane selected (of those consistently selected) BaselineCogEasyCogHardVisEasyVisHard Baseline---0.000 CogEasy---0.000 CogHard--- VisEasy---0.000 VisHard---

18. Volvo Technology Humans System Integration Volvo Technology Qualitative analysis of CogEasy vs. CogHard Almost all errors occur for CogHard..

19. Volvo Technology Humans System Integration Volvo Technology Conclusions Cognitive and visual tasks have different effects on lane changes Cognitive tasks leads only to detection/interpretation errors – changing to wrong lane or continuing straight ahead (mainly for CogHard) Visual tasks mainly induce control errors (”overshoots”) but also some detection/interpretation errors These different effects clearly visible from qualitative analysis of lane change plots The effects can also be differentiated in quantitative analysis Present quantitative results very preliminary – further analysis needed Late detections not yet looked at (promising results from Trbovich)

20. Volvo Technology Humans System Integration Volvo Technology How can these results be used in the LCT development? Provides a stronger scientific basis for the LCT – better understanding of why the deviation metric is so sensitive to both visual and cognitive load Consequences for calibration tasks – both visual and cognitive reference tasks needed (at least in theory) Specific ”control error” or ”detection error” metrics could be used to quantfy the visual and cognitive components (as complement to the standard LCT metric)