The rapid development of driver assistance systems, such as lane-departure warning (LDW) and lane-keeping support (LKS), along with widely publicized reports of automated vehicle testing, have created the expectation for an increasing amount of vehicle automation in the near future. As these systems are phased in, the coexistence of automated vehicles and human-driven vehicles on roadways will be inevitable and necessary. In order to develop automated vehicles that integrate well with those that are traditionally operated, an appropriate understanding of human driver behavior in normal traffic situations would be beneficial. Unlike many research studies that have focused on collision-avoidance maneuvering, this paper analyzes the behavior of human drivers in response to cut-in vehicles moving at similar speeds. Both automated and human-driven vehicles are likely to encounter this scenario in daily highway driving. This research has identified several possible cut-in scenario configurations that can be experienced on the highway. Data have been collected from a diverse pool of human subjects using a driving simulator with pre-programmed scenarios. To understand each driver’s behavior in response to cut-in vehicles, a novel means of visualization and analysis based on relative positions is proposed. In addition, the paper provides information on driver decision making when encountering cut-in vehicles. This could be employed as a set of guidelines for automation system behavior to ensure that they behave in a manner consistent with human-driven vehicles.