Project Abstract ADHD is one of the most common childhood disorders and often persists into adolescence—a period in which many individuals get licensed to drive. The ability to drive is important to an individual's participation in modern society, as it enhances independence and social and economic opportunity. However, motor vehicle crashes are the leading cause of death among teens. Skills that are critical in driving, including executive functioning, are frequently impaired in individuals with ADHD. Thus, research is critically needed to establish the scientific foun- dation for driving risks among teens with ADHD so that evidence-based countermeasures to reduce crash risk can be developed. Our initial R01 project established that the risk of crash involvement for newly licensed teen drivers with ADHD is 30%-40% higher than same-aged drivers without ADHD (Curry 2017 and 2019). This R01 renewal directly addresses the next logical critical gap: understanding why crash risk is elevated for teen drivers with ADHD. Our overall objective is to identify specific factors that heighten driving risks for teen drivers with ADHD. We will accomplish this with three specific aims. In Aim 1 we will identify distal factors (outside vehicle environment) that heighten risk of adverse driving outcomes for teens with ADHD. In Aim 2 we will identify prox- imal factors (within vehicle environment) that heighten risk. Finally, in Aim 3 we will examine (among drivers with ADHD) the association between ADHD-related factors—including medication use, current ADHD impairment, and the presence of co-occurringdisruptivebehavioral disorder—andadversedriving outcomes. To achieveAim 1, we will conduct a prospective cohort study of 1,000 teen-parent dyads (500 with ADHD, 500 without ADHD). Participants will complete a baseline and four wave surveys that span from the learner phase through the first 15 months of independent driving. Survey data will be linked to objective driving outcomes captured via a smartphone data logger and existing state-level administrative data on moving violations and crashes. To achieve Aims 2 and 3, we will conduct a naturalistic driving study that will include 90 teens from Study 1 as they obtain an intermediate license (10 without ADHD, 40 with ADHD and prescribed ADHD medication, 40 with ADHD and not prescribed ADHD medication). Innovative in-vehicle technology in teens' vehicles will continu- ously monitor driving patterns, behaviors, and performance for the first 12 months of licensure. We will also collect daily medication use for the first 3 months of licensure utilizing innovative ecological momentary assess- ment methods via text prompts. This will enable us to conduct the first examination of how ADHD medication use influences real-world naturalistic driving performance. We expect that the rich foundational information gen- erated from this project will provide critical knowledge about driving risks for teens with ADHD. The project will ma...