code: public GraphHopper setEncodingManager(EncodingManager em) {
          ensureNotLoaded();
          this.encodingManager = em;
          if (em.needsTurnCostsSupport())
              traversalMode = TraversalMode.EDGE_BASED_2DIR;
  
          return this;
      }
docs: Specify which vehicles can be read by this GraphHopper instance. An encoding manager defines
  how data from every vehicle is written (und read) into edges of the graph.