1. Effects of Oncoming Vehicle Size on Overtaking Judgments
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Vivian R. Nelson, Samuel J. Levulis, & Patricia R. DeLucia

2. Background Overtaking -Risky event
-Drivers must make judgements (Grey and Regan, 2005)
Levulis, S. J., DeLucia, P. R., & Jupe, J. (2015)
Overtaking
-risk
-drivers
L & d
Citation for data presented

3. Experiment 1
Purpose: Examine whether overtaking judgments are influenced by size of an oncoming vehicle
Oncoming vehicles alternated between a motorcycle, a car, or a truck on a two-lane highway
Participants were told that they should pass lead car if they felt it was safe
Participants accepted more gaps in front of the motorcycle
Results supported overtaking judgments were influenced by size
The size of vehicle was confounded with the type of the vehicle
Add task of what participants did in experiment after saying on two-lane highway
Add screenshot of what participants saw
Less text more images
A limitation of ex 1 was that size of the vehicle confounded with the type of the vehicle
While it both experiments had the limitation of would have been the perceived threat so, the perceived threat still remained after ex 2
A view of a scene.

4. Experiment 2
Purpose: To tease apart the effects of vehicle size and type
Oncoming vehicles alternated between a small motorcycle, a large motorcycle, as well as a small truck and a large truck on a two-lane highway
Participants accepted more gaps when the oncoming vehicle was a small motorcycle or a small truck compared to the large motorcycle and truck
Size, but not vehicle type influenced overtaking judgments
An alternative explanation remained: Perceived Threat
Participants may have perceived a collision with a larger vehicle as more harmful
Add task of what participants did in experiment after saying on two-lane highway
Add screenshot of what participants saw
Less text more images
A limitation of ex 1 was that size of the vehicle confounded with the type of the vehicle
While it both experiments had the limitation of would have been the perceived threat so, the perceived threat still remained after ex 2

5. The Current Study Purpose
Examine whether overtaking judgments are influenced by the size of an oncoming vehicle when the actual threat of the oncoming vehicle is removed
If we eliminate the real threat of head-on collisions will overtaking judgments still be influenced by the size of an oncoming vehicle?

6. Method Participants Twenty-four college students (12 male, 12 female)
Age ranged from 19 to 51 years old (M = 24) (SD = 7.1)
All held a driver’s license
Introduce image as it is a top down view of the scene
For

7. Method
Display
A STISIMTM driving simulator was used to depict a car-following scenario on a straight, three-lane, two-way highway
In each scene, vehicle in the oncoming lane varied in size (small motorcycle, small truck, large motorcycle, and large truck)
Auditory tone sounded 7 s after scene began
A screen shot of a scene.

8. Method Procedure Active Participants: Passive Participants
Given control of their vehicle when tone sounded
Instructed to pass if they felt they could do so before the oncoming vehicle reached the position in the road adjacent to where they would re-enter the right lane
Passive Participants
Steering and speed automatically controlled
Instructed to press one of two buttons to indicate decision
Introduce image as it is a top down view of the scene
For
A top down view of a practice scene.
Note: the red line did not appear in the experiment; nor did yellow cab appear

9. Independent Variables
Control Type
Active and passive
Manipulations
Oncoming vehicle (e.g.: small & large motorcycle + small and large truck)
Distance of oncoming vehicle (1500ft, 2000ft)
Speed of oncoming vehicle (45, 55, and 65mph)
Speed of participant's vehicle (30, 40, and 50 mph)
Note: larger versions of these vehicles were produced

10. Dependent Variables Percentage of accepted gaps
Percentage of false alarms
Sensitivity (d’)
Response bias (β)

11. Results Percentage of Accepted Gaps
Mention: there was no difference between the passive and active condition. These results will show the effect of vehicle type.

12. Results
Percentage of False Alarms

13. Results
Sensitivity

14. Results
Response Bias

15. Conclusions
Found the same effect of vehicle size as Levulis et al. (2015)
Even when the possibility of a head-on collision was removed
Suggest the effect is likely a perceptual issue (e.g., smaller vehicles are perceived to be farther away while larger vehicles are perceived to be closer)
collisions are partly due to misjudging the distance and speed of oncoming vehicles

16. Implications Drivers use perceptual cues when driving
Size-arrival-effect (Delucia, 2013)
Smaller objects are perceived as being farther away and larger objects are perceived to be closer
Development of an “overtaking assistant”
Concepts have been developed but are not commercially available
Educate drivers to help prevent accidents
Forbid overtaking within certain areas??

17. References
DeLucia, P. R. (2013). Effects of size on collision perception and implications for perceptual theory and transportation safety. Current Directions in Psychological Science, 22, Gray, R., & Regan, D. M. (2005). Perceptual processes used by drivers during overtaking in a driving simulator. Human factors, 47, Levulis, S. J., DeLucia, P. R., & Jupe, J. (2015). Effects of oncoming vehicle size on overtaking judgments. Accident Analysis & Prevention, 82,

18. Acknowledgements REU Program Dr. Delucia Lab B15 TTU Staff
This material is based upon work supported by the National Science Foundation under Grant No

19. Thank You.