Why Märklin?
The track plan above has a reverse loop. But that’s no problem for the Märklin HO system, because it is based on the 3-conductor principle, also called 3-rail system. Märklin tracks have additional contact points in the middle between the two outer rails. The electrical polarity of these contact points is positive, the outer tracks are negative. So there is no alternating polarization in a reverse loop. Just plug the tracks together and enjoy the benefit of the reversing loop in that plan: Your loco can’t shunt into the gravel pit because it’s at the front of the model train? Simply drive around the reverse loop and your wagons are ready to be pushed back!
In contrast to that, HO 2-rail systems would require special electrical wiring for reversing loops.