The route chosen with the top_speed value selects a significantly slower detour

[radekvermirovsky]

We would like to utilize the top_speed parameter in routing because the vehicles we intend to route are equipped with a speed limiter set to 85 km/h. However, when we apply the top_speed parameter, it selects significantly longer routes in terms of time, which is impractical.

For instance, when routing with a top_speed of 89 km/h, the route appears reasonable, taking 2 hours, 1 minute, and 37 seconds over a distance of 171.8 km.

valhalla.openstreetmap.de link

However, simply changing the top_speed to 88 km/h results in the route taking a substantial detour, increasing both the travel time and distance significantly (almost 2 hours in time and 24 km in distance)

I read in the documentation that top_speed is also intended to "avoid roads with higher speeds than this value." However, even when considering this, these detours that prolong travel time don't make sense.

It seems like top_speed is having the wrong impact on some costs on this highway.

We tried adjusting use_highways and use_toll to prioritize the Valhalla route over this more sensible highway route, but without success.

[radekvermirovsky]

ok seems like it was already discussed there. discussion. Now it make sense what is happening...but IMO this penalty shouldnt be there.