Closing a segment incorrectly removes turn permissions at non-adjacent intersections

[samarchie]

Summary

When using --segment-speed-file to close a road segment, OSRM removes turn permissions at intersections that are not directly connected to the closed segment. This prevents routing from open segments, even when those segments are separated from the closed segment by intermediate nodes.

Environment

• OSRM version: ghcr.io/project-osrm/osrm-backend:v6.0.0 docker image
• OSM data: New Zealand extract from Geofabrik (latest)
• Profile: car.lua (default driving profile) from https://github.com/Project-OSRM/osrm-backend/blob/master/profiles/car.lua
• System: Ubuntu LTS 22.04

Problem Description

Consider a linear road arrangement with two consecutive segments that are a part of the same way:

            |
            |
            | 
-------  Node A: -----------
         Intersection 
            |
            |
         Segment A: 
         Normal speed (40 km/h)
            |
            |
         Node B
            |
            |
         Segment B: 
         Closed segment (0 km/h)
            |
            |
         Node C:
-------  Intersection -------
Closed                 Closed

Consider a house located on Segment A (the open segment between Node A and Node B). We request a route from this house to a destination to the north.

Expected Behaviour

• Segment B: Should be avoided by routing due to prohibitive speed (✓ expected)
• Segment A: Should be fully routable with normal turn permissions at Node A (✓ expected)
• Node A: Turn permissions should be unaffected since the closed segment doesn't connect to it
• A route from the house on Segment A should successfully navigate to Node A and turn onto other roads

Actual Behaviour

When requesting a route from the house on Segment A:

• Segment A still shows 40 km/h in debug mode (correct ✓)
• Segment B correctly shows 0 km/h in debug mode (correct ✓)
• The vehicle can travel along Segment A
• However, at Node A (the intersection), turn permissions are removed or blocked
• In osrm-frontend debug mode, when approaching Node A from Segment A, the turn indicators (left/straight/right arrows) are missing
• No route can be found because the vehicle cannot execute any turn at Node A to leave Segment A

This is particularly unexpected because Node A and the closed Segment B are not directly connected - they are separated by Node B.

Visual Debug Evidence

Using osrm-frontend with debug mode enabled:

1. Segment A shows correct 40 km/h speed ✓
2. Segment B shows 0 km/h and is correctly avoided ✓
3. Traveling along Segment A toward Node A: movement is allowed ✓
4. At Node A (intersection): turn arrows are completely missing ✗
5. Result: No route possible from Segment A because the vehicle cannot leave Node A

Minimal Reproduction

# Download necessary files, such as the car profile and New Zealand OSM data
mkdir data
wget https://raw.githubusercontent.com/Project-OSRM/osrm-backend/refs/heads/master/profiles/car.lua -O data/car.lua
wget https://download.geofabrik.de/australia-oceania/new-zealand-latest.osm.pbf -O data/nz-latest.osm.pbf 

# Create a segment speed file to close a specific segment by setting the 3 segments connecting to Node B in both directions to 0 km/h
cat > data/segment_speeds.csv << EOF
5552089703,104536666,0
104536666,5552089703,0
5785426394,104536666,0
104536666,5785426394,0
5552089702,104536666,0
104536666,5552089702,0
EOF

# Extract, partition, and customize the OSRM data with the segment speed file
docker run -t -v ./data:/data --user $(id -u):$(id -g) ghcr.io/project-osrm/osrm-backend:v6.0.0 osrm-extract -p /data/car.lua /data/nz-latest.osm.pbf

docker run -t -v ./data:/data --user $(id -u):$(id -g) ghcr.io/project-osrm/osrm-backend:v6.0.0 osrm-partition /data/nz-latest.osrm

docker run -t -v ./data:/data --user $(id -u):$(id -g) ghcr.io/project-osrm/osrm-backend:v6.0.0 osrm-customize /data/nz-latest.osrm --segment-speed-file /data/segment_speeds.csv

# Start the OSRM routing server with MLD algorithm
docker run -d -it --cpus=1 -p 54781:5000 -v ./data:/data ghcr.io/project-osrm/osrm-backend:v6.0.0 osrm-routed --algorithm mld --max-table-size 100000 /data/nz-latest.osrm --threads 1

# Test a route that should be possible from Segment A to a destination north of Node A
curl "http://localhost:54781/route/v1/driving/172.73786544799805,-43.53516385006154;172.7371519804001,-43.533526582257004?overview=false&alternatives=true&steps=true"
# Response: {"message":"No route found between points","code":"NoRoute"}

# Run osrm-frontend to visualise and debug
docker run -p 9966:9966 -e OSRM_BACKEND='http://localhost:54781' ghcr.io/project-osrm/osrm-frontend:latest

Location and Real World Context

I am trying to route from 351 Estuary Road, Christchurch, New Zealand 43.535075,172.735684 (lon,lat) to a random point north of it.

[afarber]

The root cause is possibly in src/updater/updater.cpp in the compute_new_weight_and_duration():

  for (const SegmentWeight weight : weights)
  {
      if (weight == INVALID_SEGMENT_WEIGHT)
      {
          new_weight = INVALID_EDGE_WEIGHT;
          break;
      }
      new_weight += alias_cast<EdgeWeight>(weight);
  }

When any segment in a road is closed (speed=0), this code marks the entire road as invalid. So if segment C-D is closed, the earlier segments A-B and B-C also become unusable.

[samarchie]

Thanks for your insight, Alexander. I've attempted to understand, edit and test that area of the codebase to:

1. Per-segment edge weight calculation (src/updater/updater.cpp)
   • Changed from invalidating entire geometries to checking individual segment validity
   • Still didn't allow routing from Segment A-B
2. Phantom node validity fix (include/engine/geospatial_query.hpp)
   • Changed is_forward_valid_source to only check segments after the phantom node position
   • Should allow starting routes on valid segments, but hasn't worked yet
3. Process edges where either end is updated (src/updater/updater.cpp)
   • Previously, only processed edges where the source was in the segment speed file
   • Now processes edges where the source or target is updated
   • Still doesn't allow routing from Segment A-B

I might take another crack at it from the same angles. During a side quest in the second approach, I was able to enable turning back on for cars leaving Segment A-B. But a route could still not be found when starting on Segment A-B, which is weird.

Any more ideas or approaches would be greatly appreciated!

[afarber]

Hi @samarchie, the reported issue is not related to the segment speed file.

Testing shows the route between your coordinates fails even without applying any speed file - it's a baseline routing issue with fresh OSM data extraction.

You can verify this yourself:

1. Extract fresh new-zealand-latest.osm.pbf from Geofabrik
2. Run osrm-extract, osrm-partition, osrm-customize (no speed file)
3. Query the route - it will fail even without any closures applied

The official OSRM demo routes it successfully (likely using older data):
https://router.project-osrm.org/route/v1/driving/172.73786544799805,-43.53516385006154;172.7371519804001,-43.533526582257004

This appears to be a separate issue with how recent OSM data is being processed during extraction.

---

@TheMarex please still consider merging #7341 which adds a regression test guard for the data race fix in the customizer.

[samarchie]

Hi @afarber. That is very interesting, as I am unable to replicate what you achieved. I extracted a fresh PBF file from Geofabrik, followed all the steps without a speed file, and I got a route.

{
    "code": "Ok",
    "routes": [
        {
            "legs": [
                {
                    "steps": [],
                    "weight": 17.1,
                    "summary": "",
                    "duration": 17.1,
                    "distance": 190.8
                }
            ],
            "weight_name": "routability",
            "weight": 17.1,
            "duration": 17.1,
            "distance": 190.8
        }
    ],
    "waypoints": [
        {
            "hint": "V-kJgFrpCYB8AAAARAEAAAAAAAAFAAAAFA8KQ6-_s0MAAAAAqcWjQHwAAABEAQAAAAAAAAUAAADyAQAARcVLCsO0Z_1JxUsKxLRn_QAALwoAAAAA",
            "location": [172.737861, -43.535165],
            "name": "Estuary Road",
            "distance": 0.3419270367
        },
        {
            "hint": "WOkJgKLpCYAvAAAAEQAAAAAAAAAAAAAA6tRSQnc-lUEAAAAAAAAAAC8AAAARAAAAAAAAAAAAAADyAQAAfcJLCii7Z_2AwksKKbtn_QAAbxUAAAAA",
            "location": [172.737149, -43.533528],
            "name": "Estuary Road",
            "distance": 0.2667669858
        }
    ]
}

[afarber]

Yes, you are right, I have just checked with new-zealand-latest.osm.pbf (updated 2026-01-22T21:21:04Z) and the route works without the segment-speed-file but fails with it

[afarber]

Here the script I am using (I am not sure why it failed to route for me yesterday):

#!/bin/bash -e

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
BUILD_DIR="$SCRIPT_DIR/build"
PROFILE="$SCRIPT_DIR/profiles/car.lua"

WORKDIR=/tmp/osrm-7332
mkdir -p "$WORKDIR"
cd "$WORKDIR"

for bin in osrm-extract osrm-partition osrm-customize osrm-routed; do
    if [ ! -x "$BUILD_DIR/$bin" ]; then
        echo "Error: $BUILD_DIR/$bin not found. Please build OSRM first."
        exit 1
    fi
done

if [ ! -f new-zealand-latest.osm.pbf ]; then
    echo "Downloading New Zealand OSM data from Geofabrik..."
    curl -L -o new-zealand-latest.osm.pbf https://download.geofabrik.de/australia-oceania/new-zealand-latest.osm.pbf
fi

echo "=== OSM File Metadata (when was this data snapshot taken?) ==="
osmium fileinfo -e new-zealand-latest.osm.pbf
echo ""

echo "=== Timestamps of objects in the area of interest ==="
echo ""

echo "--- Way 23147610 (Ebbtide Street) history/timestamp ---"
osmium getid new-zealand-latest.osm.pbf w23147610 -f opl 2>/dev/null || echo "(Way not found)"
echo ""

echo "--- Way 23147593 (Estuary Road) history/timestamp ---"
osmium getid new-zealand-latest.osm.pbf w23147593 -f opl 2>/dev/null || echo "(Way not found)"
echo ""

echo "--- Way 116344273 (Ebbtide Street) history/timestamp ---"
osmium getid new-zealand-latest.osm.pbf w116344273 -f opl 2>/dev/null || echo "(Way not found)"
echo ""

echo "--- Node 104536666 (intersection) history/timestamp ---"
osmium getid new-zealand-latest.osm.pbf n104536666 -f opl 2>/dev/null || echo "(Node not found)"
echo ""

echo "=== Listing all objects in the area bounding box ==="
echo "Bounding box around the problem area: 172.735,-43.537,172.740,-43.532"
osmium cat new-zealand-latest.osm.pbf -f opl \
    --bbox 172.735,-43.537,172.740,-43.532 2>/dev/null | head -50 || echo "(No objects in bbox or error)"
echo ""

echo "=== Connected nodes used in segment_speeds.csv ==="
echo "Fetching nodes: 5552089703, 5785426394, 5552089702"
for nid in 5552089703 5785426394 5552089702; do
    osmium getid new-zealand-latest.osm.pbf n$nid -f opl 2>/dev/null || echo "n$nid: (not found)"
done
echo ""

echo "=== Creating segment_speeds.csv (closing segments connecting to Node B) ==="
cat > segment_speeds.csv << 'EOF'
5552089703,104536666,0
104536666,5552089703,0
5785426394,104536666,0
104536666,5785426394,0
5552089702,104536666,0
104536666,5552089702,0
EOF
cat segment_speeds.csv
echo ""

echo "========================================================================"
echo "=== PART 1: BASELINE TEST (WITHOUT segment-speed-file) ==="
echo "========================================================================"
echo ""

echo "=== Processing data with OSRM (MLD algorithm) ==="
"$BUILD_DIR/osrm-extract" -p "$PROFILE" new-zealand-latest.osm.pbf
"$BUILD_DIR/osrm-partition" new-zealand-latest.osrm
"$BUILD_DIR/osrm-customize" new-zealand-latest.osrm

echo "=== Starting osrm-routed server (baseline, no speed file) ==="
"$BUILD_DIR/osrm-routed" --algorithm mld new-zealand-latest.osrm &
ROUTED_PID=$!
sleep 3

echo "=== BASELINE Query (WITHOUT segment-speed-file): ==="
echo "From: 172.73786544799805,-43.53516385006154"
echo "To:   172.7371519804001,-43.533526582257004"
echo ""
curl -s "http://localhost:5000/route/v1/driving/172.73786544799805,-43.53516385006154;172.7371519804001,-43.533526582257004" | jq .
echo ""

kill $ROUTED_PID
sleep 1

echo "========================================================================"
echo "=== PART 2: TEST WITH segment-speed-file ==="
echo "========================================================================"
echo ""

echo "=== Re-customizing with --segment-speed-file segment_speeds.csv ==="
"$BUILD_DIR/osrm-customize" --segment-speed-file segment_speeds.csv new-zealand-latest.osrm

echo "=== Starting osrm-routed server (WITH speed file) ==="
"$BUILD_DIR/osrm-routed" --algorithm mld new-zealand-latest.osrm &
ROUTED_PID=$!
sleep 3

echo "=== Query WITH segment-speed-file: ==="
echo "From: 172.73786544799805,-43.53516385006154"
echo "To:   172.7371519804001,-43.533526582257004"
echo ""
curl -s "http://localhost:5000/route/v1/driving/172.73786544799805,-43.53516385006154;172.7371519804001,-43.533526582257004" | jq .
echo ""

kill $ROUTED_PID