## 1 Introduction  
Severe motor vehicle crashes are one of the most frequent traumas experienced in the United States (US) [1]. In 2018, the number of motor vehicle crashes exceeded 6.7 million in the US and about 2.7 million people reported injuries in the traffic accidents [2]. According to a National Institute of Mental Health (NIMH) study, about 39% of the motor vehicle accident (MVA) survivors met DSM-III-R criteria for post-traumatic stress disorder (PTSD). Patients with PTSD often experience disabling memories and anxiety related to the car accident event, and are likely to be subjectively distressed by environmental conditions with increased impairment in daily performance, such as commuting to work or driving a car for pleasure [3]. The type of PTSD that is caused by MVAs is known as a driving phobia disorder. Driving phobia is very common and the level of fear may range from mild to severe. Some patients are only afraid of specific driving conditions, while some cannot bear to sit behind the steering wheel of a motor vehicle.  
The adoption of VRET for PTSD treatments allows patients to be exposed to levels and scenarios of traumatic stimuli (or conditions) using sound, visual, and tactile immersions.  
The VRET approach follows the concept of systematic desensitization (SD), which is recognized in the field of clinical psychology for helping patients effectively overcome various phobia and anxiety disorders based on classical conditions. In some SD literature, VRET has been verified for being as effective as the traditional cognitive behavioral therapy (CBT) [4]. Using VRET, patients interact with near-real virtual representations of traumatic stimuli and scenarios to help the reduction of fears gradually and effectively. Several preliminary studies have supported the effectiveness of using VRET for driving phobia disorder [5; 6; 7], although these studies are largely case studies with qualitative perspectives. Nonetheless, the effects of VRET are confirmed to be significant when compared to traditional behavior therapy [8]. This research presents a new verification process to measure the effectiveness of VRET for driving phobia disorders. This refined VRET system, a newly modified and improved version based on our previous research, integrates the collection of the subjects' biodata via a control group-based experimental design. The in-depth biodata analysis collected from the VRET experiments, combined with the treatment group vs. control group survey analysis, is presented as the objective evidence of the VRET effectiveness.  
The paper is organized in the following sections. In Section 2, the literature review of VRET in the field of driving phobia treatment, self-measurement surveys related to driving behavior, and the patents related to VR driving applications are presented. Section 3 depicts the methodologies and approaches applied and integrated in this research. Section 4 presents the newly modified system architecture with the modules integrated to build the VRET platform for treating driving phobia disorders. Section 5 presents the analyses of survey questionnaire results and subjects' biodata during the VRET experiment. Statistical analyses, such as means and standard deviations of biodata and a one-way ANOVA are used to determine whether there are significant differences between biodata types (e.g., temperature, heart rate). Section 6 summarizes the key findings and contributions of the research. The analytical results of VRET effectiveness for treating driving phobia and the future development required in the field are addressed in the final remarks.