Cut-in maneuvers are dangerous lane changes that may result in traffic conflicts or crashes. The maneuvers affect the safety gap between vehicles and may adversely affect automated vehicle operations and safety. To comprehensively explore cut-in behavior, 4,734 cut-in events in China were extracted from the Shanghai Naturalistic Driving Study. The data were used to analyze the characteristics of cut-in behavior, including purposes, turn signal usage, duration and urgency. Cut-in duration and gap acceptance distributions were quantified and an exploratory gap model was developed to promote a broader understanding of cut-in behavior in Shanghai. The results showed that 1) cut-in behavior is relatively dangerous and risky with smaller time to collision than normal lane change, and more than 50% of cut-ins are motivated by a slow preceding vehicle; 2) almost half of Chinese drivers did not use a turn signal when cutting-in, which is indicative of poor driving habits and an aggressive driving style; 3) unlike a typical lane change, cut-ins have a shorter duration as well as a smaller lag gap. A lognormal distribution and Generalized Extreme Value distribution produced the best fit for the cut-in duration and lag gap respectively; 4) road type, relative speed, and following vehicle’s acceleration are important factors that might influence drivers’ lag gap acceptance. This paper extends the exploration and development of lane change theory and its applications. The results indicate social norms and behavior are influenced by culture and other countries should consider calibrating assumptions about cut-in behavior based on local data sources.