How does the design and implementation of a large$-$scale urban infrastructure project, such as a highway or a bridge, involve the integration of various civil engineering disciplines, including structural, geotechnical, transportation, and environmental engineering, and what are the key challenges and considerations that engineers must address to ensure the project's success in terms of safety, durability, and sustainability? Discuss the roles of each discipline in detail, the potential conflicts that can arise between them, and the strategies used to resolve these conflicts, while also considering the impact of regulatory requirements and community involvement on the project's planning and execution phases.