In developing countries such as India, the traffic on roads is highly heterogeneous in nature, with vehicles of widely varying static and dynamic characteristics. This type of traffic is characterized by lack of lane discipline and free movement over the entire width of the roadway (laneless movement) based on availability of space. In such a regime of traffic flow, the phenomenon of merging of vehicles at junctions of two roads is complex and warrants further study. Merging maneuvers at T-junctions under congested traffic conditions were studied microscopically through video recordings. On the basis of these observations, models for normal and forced merging have been developed. Video data of merging maneuvers were employed to calibrate and validate the models. Such models can be used to simulate highly congested traffic flow in a realistic manner under heterogeneous traffic conditions. They can also give insight on devising better traffic control measures at such junctions.