Problem in Routing Algortithm?

openrouteservice
1

as an OpenStreetMap user and mapper I have found a note pointing to the following pronlem:
The routing by OpenRouteService creates an illegal U turn:

https://classic-maps.openrouteservice.org/directions?n1=48.702597&n2=8.964295&n3=16&a=48.701291,8.968045,48.700175,8.960544&b=4a&c=0&k1=en-US&k2=km

The OpenStreetMap database seems to be correct, other routing systems correctly route via Mühlackerstraße.

The OpenRouteService routing is correct when I add the preference maxspeed = 100 km/h:

https://classic-maps.openrouteservice.org/directions?n1=48.706228&n2=8.959243&n3=15&a=48.701291,8.968045,48.700175,8.960544&b=4a&c=0&d=100&k1=en-US&k2=km

This looks like a problem in the algorithm.
Any idea how the OSM database can be improved in order to circumvent this issue?

2

Thanks for reaching out!

The observed behavior is caused by the fact that without any additional filters or settings such as maxspeed a routing algorithm which does not support turn restrictions is used. With some additional options active the routing is performed with a slower algorithm which takes turn restrictions into account. Another possibility to circumvent the issue is, apart from setting maxpeed, activating one of the avoidables such as ferries.

1 Like
3

Thanks so much, ANdrzej, for your fast and clear reply! It has helped me to understand the issue.

Intuitivela, I would expect that any route created by the routing algorithm is a legal route respecting the turn restrictions.

Do you think there was a conscious design decision to tolerate violations of turn restrictions?
Is this the right forum to discuss this requirement?