Cart Ruts are thought to be ancient, pre history roads system – for the transportation of building material and perhaps people. But there is no definate answer at the moment, especially for those Cart Tracks found on the islands of Malta.
The suspected reason you have these crazy deep rilles in pairs is that the many journeys by the vehicles wore away the softish rock (limestone on Malta and Gozo).
How did the vehicles move when some of the tranches can be over a meter deep? Where are the pathways worn by the humans or animals pulling the vehicels along? Did they use wooden sleds or carts with wheels?
Other suggestions are that these channels were used for irrigation of the land, that they were used to harness the natural energy flowing through the Earth like Lay Lines and Telluric Currents, or that they were used for some purpose by alien UFO’s (energy being another reason for this idea).
Some Cart Tracks in other countries go past stone quarries, so moving building material for temples and other buildings seems a reasonable idea of what the Cart Ruts were built or used for.
The sensible answer has to be that they were some form of tranportation system but for what and why and by who and when?