Most traffic offenses are not offenses that you can be arrested for, unless it’s a DUI for instance. Speeding tickets, reckless driving, you don’t get arrested on those normally. However, if they smell marijuana in the car when they come over to give you the ticket, then that might result in an arrest. Under normal circumstances, they cannot force you to allow a search, and they cannot force you to talk to them during the course of the stop. Therefore, your constitutional rights are still there. You still have the right to refuse, and you still have the right to exercise those rights.