Probably the most basic question is: what made the ruts? Sledges, carts, or travois? We might rule out sledges with runners, which couldn’t have made tracks with such a high center lane or a fluctuating distance between the ruts. (All over Malta, two ruts that run parallel together as a single track aren’t always equidistant from each other. The track can become narrower or wider, and not in any predictable way.) Wheeled carts with a central axis might also have a bit of a problem creating and negotiating such a variable track.