Which passenger windows are required to function in the up and down direction?

The requirement for passenger windows to function in the up and down direction primarily focuses on the front windows, as they are critical for driver visibility and safety. In Maine state inspections, the front driver and passenger windows must be operable to allow both the driver and front seat passenger to easily access the outdoors, communicate with people outside, and ensure proper ventilation while driving. Additionally, functional front windows contribute to the overall safety of vehicle operation, as they play a vital role in the driver's ability to check blind spots and maintain awareness of surrounding traffic conditions. While rear windows may have operational constraints, the primary focus for inspection is on the functionality of the front windows.