This study examines the combined impact of road accessibility and road capacity on urban form characteristics such as land use mix, building density, and vitality. The investigation was conducted in three cities in Sri Lanka: Colombo, Kurunegala, and Mawanalla. The study recognises the fundamental role of accessibility in shaping land use mix and urban densities and acknowledges the reciprocal relationship between transport infrastructure and land use decisions. It also recognises that the capacity of road infrastructure can influence land use choices and development patterns. Accessibility, in this context, can be thought of as the degree to which different parts of the city are well-connected and easily reachable. It includes not only the presence of roads but also their connectivity. By investigating how variations in accessibility and road capacity affect land use mix, densities, and vitality within the study areas, the study aims to discern the intricate relationships between transportation networks, land use, and density decisions. This study finds that accessibility has a stronger influence on density, land use mix, and vitality than road capacity. Further, the study finds that the influence of vehicle movement on land use mix, density, and vitality indicated a strong relationship, while the influence of pedestrian movement indicated a weak relationship. Accordingly, the findings of this study have practical implications for both transport and urban planning professionals and academics. Transport engineers can help promote desirable urban form characteristics by improving the accessibility of the road network. Urban planners can consider key findings when making zoning plans and urban development plans.