Date of Award
8-2022
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Automotive Engineering
Committee Chair/Advisor
Johnell O. Brooks
Committee Member
Yunyi Jia
Committee Member
Bing Li
Committee Member
Patrick J. Rosopa
Abstract
The purpose of this dissertation was to explore the extent to which drivers do or do not have knowledge of and experience with the anti-lock braking system (ABS) and then to explore the development and evaluation of a driving simulator task specifically designed to address emergency braking with haptic brake pedal feedback. The anti-lock braking system (ABS) was created to help drivers in emergency braking situations by preventing skidding and loss of control due to locked wheels. Vehicles with conventional (pre-ABS) brakes required the driver to “pump” the brake pedal, or to rapidly press and release the brake pedal, during an emergency braking situation. This act of rapidly pressing and releasing the brake pedal was difficult for many drivers. If the driver did not pump the brake pedal quickly enough, the result could cause the vehicle’s wheels to lock and the driver to lose control of steering and braking of the vehicle. ABS automated the pumping action for the driver by holding and releasing the brake pressure to prevent the wheels from locking and skidding. Since ABS quickly holds and releases the brake pressure, the driver experiences a vibration or “thumping” in the pedal when ABS is engaged (Kahane, 1994). This vibration or “thumping” can be confusing for the driver. The National Highway Traffic Safety Administration (NHTSA) discovered that drivers did not understand the purpose of ABS, did not know when ABS was functioning, or if their vehicle was even equipped with ABS (Mazzae, Garrott & Snyder, 2001).
In the US, teenage drivers have an increased risk of being involved in crashes. To address the increased risk of teen crashes, post-license advanced driving programs have emerged. The first study within this dissertation gained teenagers’ perspective of a half day post-license driving program focused on a hands-on introduction to emergency braking, skid recovery and the dangers of distracted driving on a closed-road track, the Guard Your Life (GYL) Challenge program. The teenagers (N=134) completed a survey immediately following the program and a subset (N=50) of those teen completed a phone interview three months later. The open-ended survey and phone interview items reflected the program’s key concepts of emergency braking, skid recovery and the dangers of distracted driving. During the follow-up phone interview, the majority of teenagers reported using the skills experienced and half of the participants who participated in the phone interview reported using skills that they learned to avoid a crash, where ABS braking was the most common skill used. Almost all teenagers reported anticipating or changing their driving behaviors, specifically by reducing distractions, having a heightened awareness and changing their driving position. The survey and follow-up phone interview results suggested that the teenagers benefited from the skills introduced and, from the teenagers’ perspective, has helped them avoid crashes. The results of the study also suggested that teen drivers do not understand or have experience activating ABS prior to the program.
During study I, it was observed that the parents of the teenage drivers were engaged during the classroom portion of the study and the majority of the parents stayed to watch their teen drive on the track. Study II gained parents’ perspectives while observing their teens’ involvement in the GYL post-license driving program which focused on a hands-on introduction to emergency braking, skid recovery and the dangers of distracted driving. Parents (N=134) completed a survey after the program, and for comparison purposes, the teens (N=164) also completed a survey at the end of the same program. While the parents only observed the program, the results revealed that most learned useful information and would consider additional training for themselves. Interestingly, though 85% of the parents reported experiencing ABS, only 53% of the parents reported teaching their teen about ABS, with 87% of those parents discussing ABS and only 13% of parents providing hands-on practice to their teen. Almost all teens and parents reported anticipating changing their driving behaviors, specifically by reducing distractions, having a heightened awareness while driving and changing their driving/seating position. These results suggested that parents benefited from simply observing the class and though many parents reported experiencing ABS, the lack of hands-on practice the parents reported providing to their teen may suggest that some of these parents may not understand ABS.
In addition to evaluating drivers’ views of the GYL program, study III aimed to gain the views of both teen and adult drivers’ views of full day car control classes designed to address defensive driving skills through both classroom instruction and hands-on practice on a closed-road track. To obtain the views from teenagers (N=80) and adults (N=177), both groups completed a survey immediately after their classes, and a subset of the adults (N=64) completed a phone interview six months later. Results from the teenage and adult surveys showed that both groups reported the most important topics learned during the car control class were skid recovery, using ABS and looking where the car should go. Both teenagers and adults reported that they plan to significantly change their driving behaviors, especially those concerning seating, hand and mirror positions. Overall, after the class, the teenagers and adults felt “moderately competent” in their ability to perform the exercises practiced during the class, which increased from the rating of “not competent” prior to the class. The results from the phone interview with the adults suggest that ABS braking was the most important topic to them six months later. ABS braking was also the single-most reported skill used after the class and the self-identified skill most used to avoid a crash. The phone interview showed that the adults accurately predicted their use of the behaviors (seating position, vision, distractions, etc.) and turned those behaviors taught during the class into habits of their daily driving. The results from the teenage and adult surveys, as well as the phone interview with the adults, suggested that the participants benefitted from the knowledge and skills gained from the one-day car control class. Like the teens in study I, the adults reported using ABS braking the most on the road after the class of all of the skills addressed, thus adult drivers may not understand or have experience activating ABS prior to the class.
Study IV narrowed the focus to determine high school students’ knowledge and experience with ABS. High school participants (N=60) with a driver’s license were recruited from science classes to complete the survey. The results revealed that only 22% of the teens knew what ABS stood for and 23% could describe the purpose of ABS. Only 33% of the teens reported using ABS and 15% reported that they had practiced using ABS. Interestingly, there were no statistical differences in knowledge or experience with ABS between teens that had taken driver’s education and those who had not. The results of the survey found the majority of teen drivers did not have knowledge of and experience with ABS. This study suggested that teen drivers, regardless of driver’s education experience, did not have knowledge of or experience with ABS.
Understanding that not all drivers may have knowledge and experience with ABS, Study V investigated how a driver’s knowledge and experience with ABS effected performance braking in a vehicle. Drivers (N=79) were recruited from adult car control classes which focused on defensive driving skills, including both classroom and behind-the-wheel instruction on a closed-road course. One focus of the class was activation of ABS, which was designed to help drivers during emergency braking situations. In the classroom, participants learned what ABS is as well as how and when it functions. On the closed-road course, participants learned how to activate ABS and how the system feels when it is activated. The goal of this study was to understand how knowledge of and experience with ABS prior to the class relates to a driver’s ability to activate ABS. The participants’ ability to activate ABS was evaluated by the driving instructors using a behaviorally anchored rating scale with five ratings, ranging from 1 representing no ABS activation to 5 corresponding to full ABS activation throughout the entire stop. Participants completed a survey before and after the class to gain an understanding of their knowledge of and experience with ABS. The results found significant differences in braking performance between participants with and without prior knowledge of the feel of ABS when activated, practice activating ABS, and training, both with and without an ABS braking component. Most of the drivers who had practice or training activating ABS were able to fully activate ABS on their first try, outperforming all other participants. These results suggested that drivers could benefit from practice focusing on emergency braking with ABS.
Study VI was a smaller study within study V, where participants (N=17) recruited from the adult car control classes. This study aimed to investigate if electrodermal activity (EDA) varied while drivers were completing the ABS exercise on the track. Participants wore Empatica E4 devices on both wrists to measure EDA. The EDA data were analyzed through skin conductance level (SCL), but the results showed no significant differences in SCL values between the right and left wrists, nor was there any consistency for which wrist had higher SCL values. The results from this study suggested that for an ABS braking task, SCL may not be the ideal measure of EDA.
Not all drivers have access to training or an experienced driver to help them practice activating ABS, thus a novel driving simulator with haptic brake pedal feedback and interactive exercise Pedals Emergency Stop© for drivers to practice emergency braking with ABS feedback was developed. The interactive exercise displayed images of a gas and brake pedal with colored target zones. The interactive exercise began with a gas pedal target that oscillates up and down, then a stationary brake pedal target appears at the very top of the brake pedal at the same time a “Stop” prompt was played. Participants were instructed to press the brake pedal as quickly as possible to move the brake indicator into the target zone and hold the indicator in the target zone for three tones. In addition, when the participant was in the target zone haptic brake pedal feedback was provided. After each braking target, the participants were presented with feedback regarding if they passed or failed that trial. To pass, participants were required to press the brake pedal fast and hard enough as well as hold the brake indicator in the target zone for three tones. If the participant did not pass the trial, they were presented with advice to improve their performance, either to “press harder and faster” or to “hold longer”.
During the initial evaluation of the emergency braking practice, participants (N=63) had 15 trials and were grouped base upon their knowledge and experience feeling ABS activate. The results found that 85% of participants were able to “pass” for the first time within the first four trials, with an average of three trials to “pass”. All participants in this study received a “pass” a minimum of two times during the practice. There were no differences in performance observed between participants with previous knowledge and experience feeling ABS versus those who did not have prior knowledge and experience with ABS. Also, participants thought they had enough practice, that the practice was a practical tool, and recommended the training for new drivers, refresher training, as well as evaluating fitness to drive. The results of this study suggested that the emergency braking practice using the Pedals Emergency Stop© interactive exercise may be an effective tool for drivers to practice emergency braking with haptic ABS feedback.
As a result of the initial evaluation of the emergency braking practice, criteria to pass the emergency braking practice was proposed. The Pedals Emergency Stop© interactive exercise was divided into a practice with four trials and three tests with four trials each. The criteria to pass the emergency braking practice was passing three out of four trials within one of the tests.
The final study within this dissertation aimed to understand if the emergency braking practice on the simulator generalized to driving in a vehicle on a closed road course as well as to evaluate the proposed criteria to pass the simulator practice. Participants (N=69) were grouped according to their previous experience feeling ABS activate as well as if they completed the simulator practice. Participants in the simulator group completed the emergency braking practice with the Pedals Emergency Stop© interactive exercise for a total of 16 trials making up the practice and three tests. All participants attempted to activate ABS on the track, where their performance braking was rated by a professional driving instructor using the behaviorally anchored rating scale developed in the study V which consisted of five ratings, ranging from 1 representing no ABS activation to 5 corresponding to full ABS activation throughout the entire stop. Participants completed five attempts on the track, all at 35mph. This speed was chosen because it is the speed where most crashes occur. Since 97% of the participants that completed the simulator practice passed the practice, the results revealed that the criteria to pass three out of four trials was representative of a participant that was successful passing the Pedals Emergency Stop©. There were no significant differences in braking performance ratings on the track between participants that had completed the simulator practice and those who had not. This was also true for participants with and without prior experience feeling ABS activate, where no differences were found in performance braking rating on the track. Though braking performance on the track was not influenced by the simulator practice, 74% of the participants that completed the simulator practice thought they benefitted and/or their performance on the track was improved as a result of the emergency braking practice on the simulator with Pedals Emergency Stop©.
Though the speed of 35mph was selected because it is the speed where most crashes occur, future studies should include multiple speeds, both lower (35-45mph) and higher speeds (50-60mph). Study V observed that speeds between 35 and 50mph corresponded to drivers learning how hard and how quickly to press the brake pedal. As the speeds increased over 50mph, the stopping distance increased, and drivers learned to maintain brake pedal position and pressure until the vehicle came to a complete stop. Future research should explore the Pedals Emergency Stop© interactive exercise with novice teen drivers, who make up a disproportionate number of fatal crashes for their small percentage of the driving population (NHTSA, 2018b). Since the majority of teenage drivers’ crashes can be attributed to driver error, which includes recognition errors (visual scanning errors, distraction), decision errors (following distance, vehicle speed relative to conditions), and performance errors (losing control; Curry, Hafetz, Kallan, Winston, & Durbin, 2011), the emergency braking practice on the simulator could help to address decision and performance related braking errors. Driver’s education is commonly included in the graduated driving license process (NHTSA, 2017a) and integrating the emergency braking practice on the simulator with driver’s education may help novice teen drivers understand emergency braking as well as the haptic brake pedal feedback associated with ABS activation through the repetition of trials as part of the Pedals Emergency Stop© interactive exercise.
As the automotive industry shifts focus to autonomous vehicles, the driving task will be eliminated and all individuals within the vehicle will become passengers. It is known from Study VII that the haptic feedback from ABS in not only in the brake pedal, but can be felt through the entire vehicle. Future autonomous vehicle users may experience the feedback from ABS as passengers. If the user does not understand the feedback nor given information about what the feedback is doing, this could lead to the user losing trust in the autonomous vehicle. Future autonomous vehicles should consider the impact that ABS feedback could have on user trust and methods to provide information to users to help communicate that the feedback back is part of normal emergency braking operation.
Recommended Citation
Mims, Lauren, "Investigating Drivers’ Knowledge and Experience With the Anti-lock Braking System (ABS) Which Led to the Development and Evaluation of an Emergency Braking Training Exercise Using a Driving Simulator With Haptic Pedal Feedback" (2022). All Dissertations. 3070.
https://tigerprints.clemson.edu/all_dissertations/3070
Author ORCID Identifier
0000-0002-3742-5841