Increasing speeds doesn't have the expected effect on duration

[rdvelazquez]

@karussell

Another factor might be because we reduce the speed according to the allowed max speed on the road.

Is there another place where I need to override this other than here: https://github.com/graphhopper/graphhopper/blob/master/core/src/main/java/com/graphhopper/routing/util/CarFlagEncoder.java#L140?