Routable road segments are connected to each other with junction nodes.
Pedestrian boardwalks and Walking Trails are the only road types which can be connected to other roads without creating such a junction node. When dragged to a drivable road segment, they instead create a virtual node, also known as a phantom node.
Phantom nodes should be used for connecting Walking Trails and Pedestrian boardwalks to drivable segments. There is no need to split drivable segment to connect WT's or PB's to the road network.