A window assembly for a vehicle includes a frame configured to mount to a transit vehicle, a fixed window panel affixed to a portion of the frame, and a movable window assembly having a movable window panel circumscribed by a movable frame. The movable frame has opposite end members and a pair of opposite slide rail members. The slide rail members are slidably received in respective channels along opposite portions of the frame. Each of the slide rail members includes a co-extruded slide rail having a semi-rigid or rigid rail portion, a flexible window seal co-extruded with the rail portion for sealing against the movable window panel, and a flexible sliding seal co-extruded with the rail portion for slidably engaging the opposite portions of the frame when the movable window assembly is assembled to the frame and is moved between its opened and closed positions.