Put the still image of the bus on a track above the two video streams being transited.
Use Pan/Crop to move the image of the bus across screen. When the bus starts moving, you'll be seeing video 1 underneath, when the bus finishes moving, you'll be seeing video 2 beneath the bus. You may want to process the bus image in Photoshop or other graphic editor first to get rid of any hard boundry lines of the image.
You could also add various blur effects, or border effects to the still image you are pan/cropping, especially if you want to add more of a feeling of motion.