1. Effects of Oncoming Vehicle Size on Overtaking Judgments
Vivian Nelson Mentor: Dr. DeLucia

2. Purpose
The purpose of this study is to examine whether overtaking judgments are influenced by the size of an oncoming vehicle even when the actual threat of the oncoming vehicle is removed.

3. Background
Passing a lead car, or overtaking, is a risk event that results in fatal collisions. When judging if it is safe to overtake, drivers must judge when oncoming cars in the opposite lane will reach them. Levulis and DeLucia conducted two experiments using a driving simulation of a car-following scene. Participants were asked to judge whether it was safe to overtake the lead car.

4. Experiment 2 Experiment 1
There was a small motorcycle and large motorcycle, as well as a small truck and large truck
Participants accepted more gaps in front of the smaller motorcycle and smaller truck than the large motorcycle and large truck.
An alternative explanation remained
Oncoming vehicles alternated between a motorcycle, a car, or a truck on a two-lane highway
Participants accepted more gaps in front of the motorcycle than in front of the car or truck.
The type of vehicle was confounded with the size of the vehicle

5. Question?
The question for the current experiment is this: 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
Simulations and task are like the prior experiments except that a three- lane road was used
Participants will judge whether it is safe to overtake the lead car before the oncoming car reaches the point in the road adjacent to where they would re-enter the right lane safely.
Passive condition and active condition
Levulis et.al (2015)

7. Independent Variables
Vehicle size and type (e.g.: small & large motorcycle + small and large truck)
Speed of oncoming vehicle
Speed of participant's vehicle
Gap size
Percentage of accepted gaps
Number of false alarms
Sensitivity
Response bias

8. Expected Results
I expect the size of an oncoming vehicle to still influence overtaking judgments, even when the real threat of head-on collision is eliminated. That is, I expect the results of the first two experiments which showed an effect of size on judgments will be supported when this alternative explanation of threat is ruled out.

9. What am I learning?
Ultimately, we will learn that overtaking collisions are partly due to misjudging the distance and speed of oncoming vehicles .

10. Practical Implications
This research can be used to improve traffic safety. For example, it could potentially lead to the development of an “overtaking assistant” in to help drivers make better decisions. At the very least, results can be used to educate drivers to help prevent accidents.

11. Thank You.