Prior to designing, you first need to gather the technical requirements. Once you have a clear set of technical requirements, then you can start the application design process. During the application design process, you also need to gather the non-technical requirements and start the architecture design process.
My requirement is that i have a junction where four roads from four direction meets. The vehicles from one direction can take the other three directions. For this system i need to do a design. What are the non functional requirements that i can think of in this design.