NY MOVES: Evaluating the Impact of New York’s Methadone Outreach VEhicleS - Methadone is a highly effective treatment for opioid use disorder and is increasingly needed to prevent overdose in the era of fentanyl. However, access to methadone in the U.S. is very limited as historically it could only be dispensed through opioid treatment programs (OTPs) operating in fixed-site locations. Most U.S. counties do not have an OTP, and federal and state regulations make it difficult to open new OTPs. As a result, most patients - and particularly those who are unhoused, institutionalized, or live in rural areas - struggle to access OTPs, exacerbating treatment and overdose in these communities. In 2021 the U.S. Drug Enforcement Administration issued a new rule allowing existing OTPs to establish mobile methadone units (MMUs). MMUs have the potential to transform methadone access by delivering methadone to areas that otherwise do not have access (e.g., rural areas), to patients who cannot travel to OTPs (e.g., incarcerated), and to other groups (e.g., unhoused) who may benefit from a low-threshold treatment environment. As a result of this rule, the New York State (NYS) Office of Addiction Services and Supports recently launched a program to support the creation of 10 MMUs across rural and urban areas of NYS by early 2025. This represents the first statewide effort to scale up MMU delivery and can provide critical lessons on the value of this intervention. However, robust evaluations of the real-world impact of MMUs are needed. The current proposal applies a mixed-methods and quasi-experimental design to conduct a comprehensive evaluation of the impact of the NYS MMU program on health outcomes, patient and provider experiences, and cost considerations that would inform sustainability long-term. Following the RE-AIM (Reach, Effectiveness, Adoption, Implementation & Maintenance) framework, we propose to (1) Assess the reach of MMUs in the first year of the program and their impact on methadone treatment initiation and retention; (2) Examine the effectiveness of MMUs in reducing overdose and acute healthcare utilization, and how this varies across patient subgroups and rural/urban areas; (3) Examine MMU adoption considerations among OTPs and ongoing implementation challenges and successes from the perspective of patients, providers, administrators, and government officials; and 4) inform maintenance considerations related to costs of operating these programs for providers and policy makers considering expanding MMUs across multiple states. This study involves a unique multi-PI partnership between academic researchers and NYS government officials that allows for unique access to administrative datasets. Additionally, a national stakeholder engagement plan will draw direct input from individuals with living experience on methadone, and widely disseminate findings to addiction providers, policy makers, and drug user groups. As such, this work responds to NIDA’s NOSI for health services and economic research to maximize availability and delivery of efficient and effective drug treatment programs, while ensuring research translation to inform real-world practices to reduce overdose.