I have not done this myself, but here is how I would approach it roughly.

Assuming that:

• the video has a constant framerate of 30 frames per second (f/s)
• there are 30 [f] * 120 [s] = 3600 frames in total
• the vehicle travelled between 2000 [m] / 120 [s] = 17 m/s and 3000 [m] / 120 [s] = 25 meters per second
• each frame is shifted at most by 25 [m/s] / 30 [f/s] = 0.8 meters each frame

For a (mosaic1) panorama you don't need a photo every 0.8 meters. I think a photo every 16 meter should be sufficient, i.e. every 20th frame.

ffmpeg is the tool I would use to extract from a video, this Stackoverflow question deals with that.

After I would have the frames (about 180) I would start stitching batches of +/-10 images in Hugin. I guess Photoshop might work, but Hugin provides far more control over the stitching process. Stitching all the 180 frames in one go sounds like something my computer (and sanity) would not be able to handle.

Once the batches are stitched, I would stitch them into the final image.

Instead of only taking every 20th frame, another clever way to reduce the number of overlapping pixels (suggested by xenoid in the comments) is to take a narrow column of pixels from each frame (e.g. 10% of the width of the whole frame) and stitch that.

Not sure how I would display the result though, as the final image would have an approximate aspect ratio of 1:240 (height:width).

Good luck, and don't forget to keep us updated on the outcome.

1) I think that's what it's called when you move the camera and take photos to stitch together.