My rights when pulled over by the police in a vehicle (uk). What reasons do they need, what can they do, what can they make me do, etc.
When a police officer pulls you over, they might ask to search your vehicle [1, 2]. Even if you think "I have nothing to hide," you should refuse a search [1]. The Fourth Amendment protects you against unreasonable searches and seizures, and a police officer doesn't have a right to search your car simply because you've been detained [2, 3]. An officer only needs reasonable suspicion to pull you over and detain you for a short period [2]. Being detained doesn't give the officer permission to enter your vehicle, so the police officer must have a permissible reason to search your vehicle [3]. The police can search your car if you give them permission, your car is impounded, they have a valid search warrant, they're arresting you, or there is probable cause [3]. Only the owner can give permission to search the car; passengers without ownership cannot [3]. Officers will have to justify the reasons for the search when they write up their police reports [1]. 
The general rights you have when you are pulled over by the police in a vehicle are firstly, that you do not have to consent to a search of the vehicle unless you are physically asked to do so [1, 2]. Secondly, if the reason you are pulled over is due to an issue with the vehicle itself, for example a broken brake light, the police are allowed to give you a vehicle defect rectification notice which basically allows you to get the vehicle fixed within a certain time period [1]. If the reason you are being pulled over is not connected to the vehicle itself, a police officer may seize the vehicle if they believe it is being used in a way which causes or is likely to cause alarm, harassment or distress [3]. A police officer can also ask to see your driving licence, insurance certificate or MOT certificate, if for any reason you don't have those documents with you you will have a week to take them to your local police station to prove you do own them [4]. After that, the police may hit you with an on the spot fine for minor offences and issue a breathaliser test if they deem it necessary [4, 5].