Instead of randomly choosing an integer to represent a road segment, a randomly chosen road vertex is chosen from the list of available vertices
Removed unused imports
The user can specify how many vehicles they want to simulate, along with their initial speeds. If nothing is specified, then the script will set five vehicles with randomly chosen speeds from a specified list of options. If only one custom speed is provided, then five vehicles will all be set to that initial speed. If two or more custom speeds are specified, then the number of custom speeds will indicate how many vehicles to add, each respectively being assigned their corresponding speed