ElevatorOnboardVertex onboardVertex = new ElevatorOnboardVertex(graph,
sourceVertexLabel + "_onboard", sourceVertex.getX(),
sourceVertex.getY(), levelName);
new ElevatorBoardEdge(offboardVertex, onboardVertex);
new ElevatorAlightEdge(onboardVertex, offboardVertex, level.longName);
// accumulate onboard vertices to so they can be connected by hop edges later
onboardVertices.add(onboardVertex);
}