As one of the major causes of fatalities and injuries in the U.S., motor vehicle crashes and their influential factors have been analyzed extensively in the last few decades. However, most existing studies on crashes primarily focus on passenger vehicles and highway segments. The studies on truck related safety issues in metropolitan areas are largely underexplored. Meanwhile, as part of the effort to relieve congestion in New York City, an Off-Hour Delivery program (OHD) is being implemented. The purpose of the program is to shift the delivery time of commercial vehicles to the off-hours (7:00 PM-6:00 AM). Intuitively, by shifting truck volume into night hours, the conflicts between trucks, pedestrians, bicycles and other vehicles are reduced, which is expected to improve the safety situation. However, there is also concern that lighting condition and driver fatigue during night hours could worsen the situation. In response to these concerns, this study will examine whether shifting truck deliveries to night hours has an impact on crash occurrence and severity level of crashes based on observed data over the last several years in the New York City. In pursuit of this goal, this study will achieve the following objectives: 1. Compile and process empirical datasets from multiple sources to develop a comprehensive truck accident dataset. The dataset should contain most variables that are likely to contribute to the “temporal effect”, such as lighting condition, driver fatigure, and traffic volumes of all road users; 2. Develop rigorous statistical models that can jointly analyze crash occurrence and severity, quantifying influence of temporal effect and other potentially influential factors; and 3. Based on the findings, assess the impacts of the OHD program on the safety condition in New York City, and propose strategies to maximize its positive influence while mitigating the negative influence. This research is highly relevant to the region and the nation. The data, the model and the insights to be gained from the research will contribute to the understanding of how Off-Hour Delivery may influence the truck related safety condition. This will help transportation agencies develop more efficient strategies to manage truck traffic. By doing so, this study will benefit Focus Area 3: “Promoting freight productivity, efficiency, and sustainability through multi-modal policy, planning, and logistics.” It will also contribute to the Focus Area 5: “Planning, monitoring, and implementation of communications and other technologies to understand and improve multi-modal transportation safety.”