Given ordinary circumstances, a police officer is not allowed to conduct a vehicle search. You do not want to give him/her some excuse to do so. There are four common reasons why a vehicle may be searched:
A vehicle may be searched if an officer sees an attempt to hide or dispose of anything. That is, if the officer sees you throw something out the window or attempt to hide something under the seat, he/she has the right to search the vehicle. From the moment the officer reaches your rear bumper, every one of your actions is being observed. Keep this in mind and try to avoid suspicious and furtive actions.
A vehicle may be searched if the police officer has reason to believe that the driver or passengers are armed, dangerous, or involved in criminal activity. Reasonable suspicion is also grounds for a pat down.
If there are any illegal objects in plain view, the officer has the right to confiscate them. That is, if, from the outside of the vehicle, the officer sees open containers of alcohol, drugs, or drug paraphernalia, he/she can open the door and take the illegal objects. Any other illegal objects seen while removing the initial illegal object can also be confiscated.
A vehicle may be searched if the driver or any passenger is arrested. If the driver is arrested and the vehicle is towed, police officers may conduct a search of the inventory of the vehicle, even if there is no basis to suspect the presence of illegal objects.