Yeah, wow, take a deep breath and analyze the complexities here. PaulS is pointing out very valid but only a handful of possibly countless situations you need to handle.
Break down your task ( learn C++ ), prepare for a long haul, there is more than just learning to program C++ required to complete a project like this. To analyze a busy street you will need multiple tasks running simultaneously with complex signal processing, not to mention everything else. Keep this as a project for when you have enough mileage in the required range of skills.