This paper investigates the effect of heavy commercial vehicles on traffic characteristics and operation of freeway merging sections. Freeways are designed to facilitate the flow of traffic, including passenger cars and trucks. The impact of these different vehicle types is not uniform, creating problems in freeway operations and safety, particularly in the vicinity of merging sections. There have been very few studies that are concerned with the traffic behavior and characteristics of heavy vehicles in these situations. Therefore, a three-year study was undertaken to investigate traffic behavior and operating characteristics during the merging process under congested traffic conditions. First extensive traffic data collection captured a wide range of traffic and geometric information using detectors, videotaping, and surveys at several interchanges. The macroscopic detector data were used to identify and quantify the impact of heavy commercial vehicles on the capacity of merging sections. Subsequently, the microscopic data were utilized to establish a model for the behavior of drivers at merging sections. Based on this behavioral model, a microsimulation program was developed to simulate the actual traffic conditions. This model was used to evaluate the capacity of a merging section for a given geometric design and traffic flow condition. In addition, this model was employed to develop a variety of intelligent transport system control strategies that are associated with heavy commercial vehicles with the goal of designing safer and less-congested freeway merging points. The implementation of the proposed control strategies showed significant improvement over the capacity of merging sections.