Graphhopper java library to travel time calculation

How can graphhopper give me precise route travel time given…

  1. In Code, I see that it uses default speed(based on road type: highway, street etc.)
  2. The routes are based on OpenStreetMaps, it doesn’t take into account current or historic traffic in any way.
  3. Why you recommend me using weighting, I though it would be more around following:
    https://www.graphhopper.com/blog/2015/04/08/visualize-and-handle-traffic-information-with-graphhopper-in-real-time-for-cologne-germany-koln/
    OR
    Insert traffic data into graphhopper