For our use case (Food service deliveries) the time/traffic thing is an issue. We are seeing our users using delivery windows to try to bias Graphhopper away from known rush hour blackspots and, of course, getting it wrong
If Graphhopper could use something like a weighted average over the past few weeks of traffic speed that would go a long way towards solving the problem (routes are planned and loaded the night before so live traffic is no help).
One related thought… I wonder how many Graphhopper users are capturing GPS info as the vehicles progress through the day. We are and I’d be quite happy to share that data with Graphhopper so you could build your own real-world speed tables for roads.
The data we have is ‘only’ from a mobile phone’s GPS so it’s not wonderfully accurate but you’re good at clever mathematics so could hopefully ‘normalise’ the data.