1. ENVIRONMENTAL DISTRACTION
ON TRAFFIC CONTROL
INFRASTRUCTURE CONSPICUITY
Johannes BEZUIDENHOUT
Prakash RANJITKAR
Roger DUNN

2. Visual Memory
• Sensory memory = 1-2s
• Working memory = < 15s then deterioration
(6 objects)
• Long term associative =

3. Visual Expectancy
Target location (Martens, M.J. & Fox, M.R.J, 2007)
– Sign location wrong-
• searched obvious location, then some delay in finding
expected sign
– Sign not expected –
• large delay or missed
– Differences in outcome:
• Experience or network knowledge
• Expectation
• Habit missing new or changed signs

4. Eye Tracker Set-up

5. Complexity of Driving Environment

6. Environmental Distractions

7. Typical Non-distracted

8. Hazard Distraction

9. Reflexive Socio-cognitive
Distraction

10. Social Distraction

11. Consequences of Hazard/Distraction
Slowed Response
• Delayed reaction
+1.5s
• Reflexive socio-
cognitive processing
• Mental workload –
hysteresis effect
Change Detection
• Vehicles more
difficult than signs
• Visual/cognitive load
decreases peripheral
vision

12. Red-light Running
8 sec
6 sec
4 sec
2 sec

13. Probability of Stopping

14. 10%
stop
90%
stop
Dilemma Zone

15. Gaze Traces

16. Gaze Heatmap

17. Fixation

18. Dynamic Hazards

19. Dynamic Hazards

20. Dynamic Hazards

21. Distraction - Cyclist

22. Dynamic Distraction vs. Hazard
Cyclist&Car

23. Time to First Fixation from 112m
• No distraction Karo 2 – 71% fixated
• Took 1.81s on average
• Distraction Karo 1 - 59% failed to fixate signal over
entire 8s
• Remainder took 3.85s from 8s mark from approach
• 2s difference in delayed reaction
Road AoI Mean
(s)
Stdev Sample
fixated
Significant
difference @
5%
Willis Signals_
L_R
5.24 3.23 71% KaroVicL2
KaroVicL1 Signals_
L_R
3.85 2.77 41% -
KaroVicL2 Signals_
L_R
1.81 1.53 71% Willis

24. 8s Mean Pursuit Fixation Time
Hazard-
Cycle
Signal L_R Signal L_R Car_Foll.
Distraction
Pl
Distraction
Pr
Signal L
KaroVicL1 KaroVicL2 Willis
Total 1.151 0.491 0.490 1.535 0.369 0.324 0.383
0.000
0.200
0.400
0.600
0.800
1.000
1.200
1.400
1.600
1.800
Meanfixationduration(s)

25. Missed Signal: Peer Proxy

26. Queue compression

27. Mean Pursuit Fixation Duration per
2s Segment
Hazar
d-
Cycle
Signal
L_R
Signal
L_R
Car_F
oll.
Distra
ction
Pl
Distra
ction
Pr
Signal
L
KaroVicL1 KaroVicL2 Willis
Average of 8s-6s 0.037 0.040 0.125 0.474 0.087 0.045 0.025
Average of 6s-4s 0.335 0.132 0.130 0.425 0.021 0.080 0.000
Average of 4s-2s 0.264 0.020 0.148 0.455 0.000 0.106 0.005
Average of 2s-0s 0.378 0.097 0.000 0.000 0.000 0.017 0.017
Average of Sig R 2s-0s 0.093
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0.400
0.450
0.500
Meanpursuitfixationtime(s)
60%
missed
30%
missed

28. Discussion
• Dynamic hazard – pedestrians, cyclists,
vulnerable road users, etc.
• Distraction 30-60% miss signal
• Pursuit fixation on signal over 8s = 490ms
• Discharging queue commanded 1500ms
• Cyclist commanded 1200ms
?