Add left-hand traffic demo maps and validation tests

assets/maps/demo/lht/01_two_lane_oneway.xodr

@@ -0,0 +1,33 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- Left-hand traffic one-way corridor with two driving lanes.
+     Per OpenDRIVE LHT, positive lane IDs travel in +s.
+     Lane +1 is nearer the median; lane +2 is nearer the left curb (slower). -->
+<OpenDRIVE>
+  <header revMajor="1" revMinor="6" name="lht_two_lane_oneway" version="1.0" date="2026-07-19"/>
+  <road name="LHT Two Lane Oneway" length="40.0" id="1" junction="-1" rule="LHT">
+    <type s="0" type="town">
+      <speed max="50" unit="km/h"/>
+    </type>
+    <planView>
+      <geometry s="0" x="0" y="0" hdg="0" length="40.0">
+        <line/>
+      </geometry>
+    </planView>
+    <lanes>
+      <laneOffset s="0" a="0" b="0" c="0" d="0"/>
+      <laneSection s="0">
+        <left>
+          <lane id="2" type="driving" level="false">
+            <width sOffset="0" a="3.5" b="0" c="0" d="0"/>
+          </lane>
+          <lane id="1" type="driving" level="false">
+            <width sOffset="0" a="3.5" b="0" c="0" d="0"/>
+          </lane>
+        </left>
+        <center>
+          <lane id="0" type="none" level="false"/>
+        </center>
+      </laneSection>
+    </lanes>
+  </road>
+</OpenDRIVE>

assets/maps/demo/lht/02_three_lane_speeds.xodr

@@ -0,0 +1,38 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- Left-hand traffic one-way with three lanes and explicit per-lane speeds.
+     +1 (median / faster) 80 km/h, +2 (middle) 60 km/h, +3 (curb / slower) 40 km/h. -->
+<OpenDRIVE>
+  <header revMajor="1" revMinor="6" name="lht_three_lane_speeds" version="1.0" date="2026-07-19"/>
+  <road name="LHT Three Lane Speeds" length="50.0" id="2" junction="-1" rule="LHT">
+    <type s="0" type="town">
+      <speed max="60" unit="km/h"/>
+    </type>
+    <planView>
+      <geometry s="0" x="0" y="0" hdg="0" length="50.0">
+        <line/>
+      </geometry>
+    </planView>
+    <lanes>
+      <laneOffset s="0" a="0" b="0" c="0" d="0"/>
+      <laneSection s="0">
+        <left>
+          <lane id="3" type="driving" level="false">
+            <width sOffset="0" a="3.5" b="0" c="0" d="0"/>
+            <speed sOffset="0" max="40" unit="km/h"/>
+          </lane>
+          <lane id="2" type="driving" level="false">
+            <width sOffset="0" a="3.5" b="0" c="0" d="0"/>
+            <speed sOffset="0" max="60" unit="km/h"/>
+          </lane>
+          <lane id="1" type="driving" level="false">
+            <width sOffset="0" a="3.5" b="0" c="0" d="0"/>
+            <speed sOffset="0" max="80" unit="km/h"/>
+          </lane>
+        </left>
+        <center>
+          <lane id="0" type="none" level="false"/>
+        </center>
+      </laneSection>
+    </lanes>
+  </road>
+</OpenDRIVE>

assets/maps/demo/lht/03_two_way.xodr

@@ -0,0 +1,41 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- Left-hand traffic two-way road.
+     +s travel on left (positive IDs); -s travel on right (negative IDs).
+     Each direction has a faster median lane and a slower curb lane. -->
+<OpenDRIVE>
+  <header revMajor="1" revMinor="6" name="lht_two_way" version="1.0" date="2026-07-19"/>
+  <road name="LHT Two Way" length="60.0" id="3" junction="-1" rule="LHT">
+    <type s="0" type="town">
+      <speed max="50" unit="km/h"/>
+    </type>
+    <planView>
+      <geometry s="0" x="0" y="0" hdg="0" length="60.0">
+        <line/>
+      </geometry>
+    </planView>
+    <lanes>
+      <laneOffset s="0" a="0" b="0" c="0" d="0"/>
+      <laneSection s="0">
+        <left>
+          <lane id="2" type="driving" level="false">
+            <width sOffset="0" a="3.5" b="0" c="0" d="0"/>
+          </lane>
+          <lane id="1" type="driving" level="false">
+            <width sOffset="0" a="3.5" b="0" c="0" d="0"/>
+          </lane>
+        </left>
+        <center>
+          <lane id="0" type="none" level="false"/>
+        </center>
+        <right>
+          <lane id="-1" type="driving" level="false">
+            <width sOffset="0" a="3.5" b="0" c="0" d="0"/>
+          </lane>
+          <lane id="-2" type="driving" level="false">
+            <width sOffset="0" a="3.5" b="0" c="0" d="0"/>
+          </lane>
+        </right>
+      </laneSection>
+    </lanes>
+  </road>
+</OpenDRIVE>

tests/domains/driving/test_lht_driving.py

@@ -0,0 +1,104 @@
+"""Driving-domain tests on left-hand traffic demo maps."""
+
+import inspect
+from pathlib import Path
+
+import pytest
+
+from tests.utils import compileScenic, sampleScene
+
+pytestmark = pytest.mark.filterwarnings(
+    "ignore::scenic.formats.opendrive.OpenDriveWarning"
+)
+
+LHT = Path(__file__).resolve().parents[3] / "assets" / "maps" / "demo" / "lht"
+
+ALL_MAPS = (
+    "01_two_lane_oneway.xodr",
+    "02_three_lane_speeds.xodr",
+    "03_two_way.xodr",
+)
+
+template = inspect.cleandoc(
+    """
+    param map = r'{map}'
+    param map_options = dict(useCache=False)
+    model scenic.domains.driving.model
+    """
+)
+
+basicScenario = inspect.cleandoc(
+    """
+    lane = Uniform(*network.lanes)
+    ego = new Car in lane
+    follower = new Car on visible lane.centerline
+    """
+)
+
+fasterLaneScenario = inspect.cleandoc(
+    """
+    candidates = [lane for lane in network.lanes if lane.sections[0]._fasterLane]
+    require len(candidates) > 0
+    lane = Uniform(*candidates)
+    ego = new Car in lane
+    other = new Car in lane.sections[0].fasterLane.lane
+    """
+)
+
+slowerLaneScenario = inspect.cleandoc(
+    """
+    candidates = [lane for lane in network.lanes if lane.sections[0]._slowerLane]
+    require len(candidates) > 0
+    lane = Uniform(*candidates)
+    ego = new Car in lane
+    other = new Car in lane.sections[0].slowerLane.lane
+    """
+)
+
+
+def _compile(path, code):
+    preamble = template.format(map=path)
+    return compileScenic(preamble + "\n" + code, mode2D=True)
+
+
+def _sample_two_car_scene(name, scenario_code):
+    scenario = _compile(LHT / name, scenario_code)
+    scene = sampleScene(scenario, maxIterations=1000)
+    assert len(scene.objects) == 2
+    ego, other = scene.objects
+    assert ego is scene.egoObject
+    return ego, other
+
+
+@pytest.mark.parametrize("name", ALL_MAPS)
+def test_lht_basic_car_placement(name):
+    """Ego and a second car can be placed on the same sampled lane."""
+    ego, follower = _sample_two_car_scene(name, basicScenario)
+
+    assert ego.lane is follower.lane
+    assert ego.laneSection.lane is follower.laneSection.lane
+    assert follower.lane.containsPoint(follower.position)
+
+
+@pytest.mark.parametrize("name", ALL_MAPS)
+def test_lht_faster_lane_placement(name):
+    """Ego sits on a slower lane; other is placed on its fasterLane neighbor."""
+    ego, other = _sample_two_car_scene(name, fasterLaneScenario)
+
+    ego_sec = ego.laneSection
+    assert ego_sec._fasterLane is not None
+    assert other.lane is ego_sec.fasterLane.lane
+    assert other.lane is not ego.lane
+    assert other.laneSection.lane is ego_sec.fasterLane.lane
+
+
+@pytest.mark.parametrize("name", ALL_MAPS)
+def test_lht_slower_lane_placement(name):
+    """Ego sits on a faster lane; other is placed on its slowerLane neighbor."""
+    ego, other = _sample_two_car_scene(name, slowerLaneScenario)
+
+    ego_sec = ego.laneSection
+    assert ego_sec._slowerLane is not None
+    assert other.lane is ego_sec.slowerLane.lane
+    assert other.lane is not ego.lane
+    assert other.laneSection.lane is ego_sec.slowerLane.lane

tests/formats/opendrive/test_lht.py

@@ -0,0 +1,163 @@
+"""Left-hand traffic OpenDRIVE maps — centerlines and faster/slower lanes."""
+
+from pathlib import Path
+
+import pytest
+
+from scenic.core.distributions import RejectionException
+from scenic.domains.driving.roads import Network
+
+pytestmark = pytest.mark.filterwarnings(
+    "ignore::scenic.formats.opendrive.OpenDriveWarning"
+)
+
+DEMO = Path(__file__).resolve().parents[3] / "assets" / "maps" / "demo" / "lht"
+
+ALL_MAPS = (
+    "01_two_lane_oneway.xodr",
+    "02_three_lane_speeds.xodr",
+    "03_two_way.xodr",
+)
+
+
+def load(name):
+    return Network.fromFile(DEMO / name, useCache=False)
+
+
+def section_by_id(network, od_id):
+    for road in network.roads:
+        for sec in road.sections:
+            if od_id in sec.lanesByOpenDriveID:
+                return sec.lanesByOpenDriveID[od_id]
+    raise AssertionError(f"no lane section with OpenDRIVE id {od_id}")
+
+
+def centerline_delta(lane):
+    pts = lane.centerline.points
+    return pts[-1][0] - pts[0][0], pts[-1][1] - pts[0][1]
+
+
+def carriageway_groups(road):
+    if road.forwardLanes:
+        yield road.forwardLanes
+    if road.backwardLanes:
+        yield road.backwardLanes
+
+
+def assert_faster_slower(network, sec, *, faster_id, slower_id):
+    faster = section_by_id(network, faster_id) if faster_id else None
+    slower = section_by_id(network, slower_id) if slower_id else None
+    assert sec._fasterLane is faster
+    assert sec._slowerLane is slower
+    if faster_id is None:
+        with pytest.raises(RejectionException):
+            _ = sec.fasterLane
+    else:
+        assert sec.fasterLane is faster
+    if slower_id is None:
+        with pytest.raises(RejectionException):
+            _ = sec.slowerLane
+    else:
+        assert sec.slowerLane is slower
+
+
+@pytest.mark.parametrize(
+    "name, n_lanes, oneway",
+    [
+        ("01_two_lane_oneway.xodr", 2, True),
+        ("02_three_lane_speeds.xodr", 3, True),
+        ("03_two_way.xodr", 4, False),
+    ],
+)
+def test_lht_network_structure(name, n_lanes, oneway):
+    network = load(name)
+    road = network.roads[0]
+
+    assert len(network.roads) == 1
+    assert len(network.lanes) == n_lanes
+    assert road.is1Way is oneway
+
+    for lane in network.lanes:
+        assert not lane.polygon.is_empty
+        assert lane.polygon.is_valid
+        for sec in lane.sections:
+            assert sec.containsRegion(sec.centerline, tolerance=0.5)
+            assert sec.containsRegion(sec.leftEdge, tolerance=0.5)
+            assert sec.containsRegion(sec.rightEdge, tolerance=0.5)
+
+
+@pytest.mark.parametrize("name", ALL_MAPS)
+def test_centerlines_follow_traffic_flow(name):
+    """Centerlines point with traffic; orientation matches flow at lane midpoints."""
+    road = load(name).roads[0]
+
+    for group in carriageway_groups(road):
+        deltas = [centerline_delta(lane) for lane in group.lanes]
+        signs = [1 if dx > 0 else -1 if dx < 0 else 0 for dx, _ in deltas]
+        assert 0 not in signs, f"{name}: zero-length centerline"
+        assert len(set(signs)) == 1, f"{name}: mixed centerline directions {deltas}"
+
+        for lane in group.lanes:
+            pt = lane.centerline.pointAlongBy(0.5, normalized=True)
+            dirs = road.network.nominalDirectionsAt(pt)
+            assert pytest.approx(lane.orientation[pt]) in dirs
+            assert lane.containsPoint(pt)
+
+    if not road.is1Way:
+        fwd = centerline_delta(road.forwardLanes.lanes[0])[0]
+        bwd = centerline_delta(road.backwardLanes.lanes[0])[0]
+        assert fwd * bwd < 0
+
+
+def test_two_lane_faster_slower_toward_median():
+    network = load("01_two_lane_oneway.xodr")
+    assert_faster_slower(network, section_by_id(network, 2), faster_id=1, slower_id=None)
+    assert_faster_slower(network, section_by_id(network, 1), faster_id=None, slower_id=2)
+
+
+def test_three_lane_faster_slower_chain():
+    network = load("02_three_lane_speeds.xodr")
+    assert_faster_slower(network, section_by_id(network, 3), faster_id=2, slower_id=None)
+    assert_faster_slower(network, section_by_id(network, 2), faster_id=1, slower_id=3)
+    assert_faster_slower(network, section_by_id(network, 1), faster_id=None, slower_id=2)
+
+
+def test_two_way_faster_slower_each_carriageway():
+    network = load("03_two_way.xodr")
+    assert_faster_slower(network, section_by_id(network, 2), faster_id=1, slower_id=None)
+    assert_faster_slower(network, section_by_id(network, 1), faster_id=None, slower_id=2)
+    assert_faster_slower(
+        network, section_by_id(network, -2), faster_id=-1, slower_id=None
+    )
+    assert_faster_slower(
+        network, section_by_id(network, -1), faster_id=None, slower_id=-2
+    )
+
+
+@pytest.mark.parametrize("name", ALL_MAPS)
+def test_lane_adjacency_helpers(name):
+    """shiftedBy, faster/slower neighbors, and same-direction constraints."""
+    network = load(name)
+    for road in network.roads:
+        for sec in road.sections:
+            for lane_sec in sec.lanes:
+                neighbors = {lane_sec._laneToLeft, lane_sec._laneToRight} - {None}
+                if lane_sec._laneToLeft:
+                    assert lane_sec.shiftedBy(1) is lane_sec._laneToLeft
+                    if lane_sec._laneToLeft.isForward == lane_sec.isForward:
+                        assert lane_sec._laneToLeft.shiftedBy(-1) is lane_sec
+                if lane_sec._laneToRight:
+                    assert lane_sec.shiftedBy(-1) is lane_sec._laneToRight
+                    if lane_sec._laneToRight.isForward == lane_sec.isForward:
+                        assert lane_sec._laneToRight.shiftedBy(1) is lane_sec
+                if lane_sec._fasterLane:
+                    assert lane_sec._fasterLane in neighbors
+                    assert lane_sec._fasterLane.isForward == lane_sec.isForward
+                if lane_sec._slowerLane:
+                    assert lane_sec._slowerLane in neighbors
+                    assert lane_sec._slowerLane.isForward == lane_sec.isForward
+
+    if name == "03_two_way.xodr":
+        road = network.roads[0]
+        assert road.forwardLanes._opposite is road.backwardLanes
+        assert road.backwardLanes.opposite is road.forwardLanes