How to prevent unlawfull u-turns

Developers
1

Hi everyone, I am a little stuck figuring out a specific u-turn. I am hosting the latest Graphhopper version with a very recent planet osm file and got a user who noticed a unlawfull u-turn.

afbeelding
afbeelding860×627 167 KB

Which I agree with. First i asumed the relation was wrong in OSM data, and even edited a small section in JOSM to see it that is the case. However, using GraphHopper Maps | Route Planner on the same stretch, it does correctly finds an alternative.

afbeelding
afbeelding1449×864 107 KB

Which is good! However, I am clearly missing some important configuration preventing non existing u-turn places.

Custom model

{
  "distance_influence": 90,
  "priority": [
    { "if": "!car_access", "multiply_by": "0" },
    { "if": "road_access == DESTINATION || road_access == PRIVATE", "multiply_by": "0.1" }
  ],
  "speed": [
    { "if": "true", "limit_to": "car_average_speed" }
  ]
}

Profile defined in config

    - name: car
      turn_costs:
        vehicle_types: [ "motor_vehicle", "motorcar" ]
        u_turn_costs: 1
        left_turn_costs: 1
        right_turn_costs: 1
        sharp_left_turn_costs: 2
        sharp_right_turn_costs: 2
      custom_model_files: [car.json]

...

profiles_lm: [bike, foot, car]

How i then post the route request

{"profile":"car","calc_points":true,"instructions":true,"points_encoded":false,"points":[[6.1407673358917,51.998575521226],[6.1372321844101,51.998066891662],[6.1375594139099,51.998846347597]],"snap_preventions":[],"ch.disable":true,"custom_model":{"priority":[],"u_turn_costs":50000000}}

I think i posted all the relevant information. I am using a few extra custom parsers and use more priority statements to prefer certain roads when calculating routes. However, that should and must not influence finding valid routes.

I would love to know what im doing wrong!

2

Hi

Maybe try setting the u-turn costs to a higher number (test with something huge like 1000), it may be that the alternative route is just much further and so the cost of 1 does not convince the engine to skp that turn.

I believe setting the cost to -1 is the equivalent of blocking u-turns as it means infinite cost.

3

Correct me if im wrong, but this will also have a global effect right? It is okay if an u-turn is needed for the shortest route, but I dont want u-turns where this is not allowed.

Sidenote, the reason i introduced slight penalties for right and left turns is because I noticed that sometimes a route goes off and on the motorway, presumably to avoid a small part when I discourage use of motorways in priority rules. However this is off topic for my main question.

4

In your first screenshot it looks like you selected the foot profile? Turn restrictions won’t apply to pedestrians. Then again pedestrians should not be allowed on this highway N338?!

5

Ah true, I usualy use leaflet to visualize graphhopper results and did not see the profile selection. I included the car profile in a picture.

afbeelding
afbeelding912×455 156 KB

However, you raise a good point. I do use the default foot profile shipped with the code.
Foot profile json

{
  "priority": [
    { "if": "!foot_access || hike_rating >= 2 || mtb_rating > 2", "multiply_by": "0" },
    { "else": "", "multiply_by": "foot_priority"},
    { "if": "country == DEU && road_class == BRIDLEWAY && foot_road_access != YES", "multiply_by": "0" },
    { "if": "foot_road_access == PRIVATE", "multiply_by": "0" }
  ],
  "speed": [
    { "if": "true", "limit_to": "foot_average_speed" }
  ]
}

Config file

    - name: foot
      custom_model_files: [foot.json, foot_elevation.json]
6

For the car profile configuration you showed the route should be illegal because of this turn restriction: Relation: 16764719 | OpenStreetMap
My next best guess why it is ignored in your case is that your OSM data might be outdated?