diff --git a/examples/01_simple_route.png b/examples/01_simple_route.png
index 98f7b4b..6b63fe2 100644
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diff --git a/examples/02_congestion_resolution.png b/examples/02_congestion_resolution.png
index 509e11a..ca9b9a4 100644
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diff --git a/examples/03_locked_paths.png b/examples/03_locked_paths.png
index 0fbcf32..099ffc2 100644
Binary files a/examples/03_locked_paths.png and b/examples/03_locked_paths.png differ
diff --git a/examples/04_sbends_and_radii.png b/examples/04_sbends_and_radii.png
index a736212..ff14c26 100644
Binary files a/examples/04_sbends_and_radii.png and b/examples/04_sbends_and_radii.png differ
diff --git a/examples/05_orientation_stress.png b/examples/05_orientation_stress.png
index 20556c3..fa89785 100644
Binary files a/examples/05_orientation_stress.png and b/examples/05_orientation_stress.png differ
diff --git a/examples/06_bend_collision_models.png b/examples/06_bend_collision_models.png
index 09eeeea..cbab4de 100644
Binary files a/examples/06_bend_collision_models.png and b/examples/06_bend_collision_models.png differ
diff --git a/inire/geometry/collision.py b/inire/geometry/collision.py
index e2d79cc..5fd5531 100644
--- a/inire/geometry/collision.py
+++ b/inire/geometry/collision.py
@@ -16,8 +16,8 @@ class CollisionEngine:
     """
     __slots__ = (
         'clearance', 'max_net_width', 'safety_zone_radius',
-        'static_index', 'static_geometries', 'static_prepared', '_static_id_counter',
-        'dynamic_index', 'dynamic_geometries', '_dynamic_id_counter'
+        'static_index', 'static_geometries', 'static_dilated', 'static_prepared', '_static_id_counter',
+        'dynamic_index', 'dynamic_geometries', 'dynamic_dilated', '_dynamic_id_counter'
     )
 
     clearance: float
@@ -47,21 +47,24 @@ class CollisionEngine:
         self.max_net_width = max_net_width
         self.safety_zone_radius = safety_zone_radius
 
-        # Static obstacles: store raw geometries to avoid double-dilation
+        # Static obstacles
         self.static_index = rtree.index.Index()
-        self.static_geometries: dict[int, Polygon] = {}  # ID -> Polygon
-        self.static_prepared: dict[int, PreparedGeometry] = {}  # ID -> PreparedGeometry
+        self.static_geometries: dict[int, Polygon] = {}  # ID -> Raw Polygon
+        self.static_dilated: dict[int, Polygon] = {}     # ID -> Dilated Polygon (by clearance)
+        self.static_prepared: dict[int, PreparedGeometry] = {}  # ID -> Prepared Dilated
         self._static_id_counter = 0
 
         # Dynamic paths for multi-net congestion
         self.dynamic_index = rtree.index.Index()
         # obj_id -> (net_id, raw_geometry)
         self.dynamic_geometries: dict[int, tuple[str, Polygon]] = {}
+        # obj_id -> dilated_geometry (by clearance/2)
+        self.dynamic_dilated: dict[int, Polygon] = {}
         self._dynamic_id_counter = 0
 
     def add_static_obstacle(self, polygon: Polygon) -> None:
         """
-        Add a static obstacle (raw geometry) to the engine.
+        Add a static obstacle to the engine.
 
         Args:
             polygon: Raw obstacle geometry.
@@ -69,23 +72,31 @@ class CollisionEngine:
         obj_id = self._static_id_counter
         self._static_id_counter += 1
 
+        dilated = polygon.buffer(self.clearance)
         self.static_geometries[obj_id] = polygon
-        self.static_prepared[obj_id] = prep(polygon)
-        self.static_index.insert(obj_id, polygon.bounds)
+        self.static_dilated[obj_id] = dilated
+        self.static_prepared[obj_id] = prep(dilated)
+        self.static_index.insert(obj_id, dilated.bounds)
 
-    def add_path(self, net_id: str, geometry: list[Polygon]) -> None:
+    def add_path(self, net_id: str, geometry: list[Polygon], dilated_geometry: list[Polygon] | None = None) -> None:
         """
-        Add a net's routed path (raw geometry) to the dynamic index.
+        Add a net's routed path to the dynamic index.
 
         Args:
             net_id: Identifier for the net.
             geometry: List of raw polygons in the path.
+            dilated_geometry: Optional list of pre-dilated polygons (by clearance/2).
         """
-        for poly in geometry:
+        dilation = self.clearance / 2.0
+        for i, poly in enumerate(geometry):
             obj_id = self._dynamic_id_counter
             self._dynamic_id_counter += 1
+            
+            dil = dilated_geometry[i] if dilated_geometry else poly.buffer(dilation)
+            
             self.dynamic_geometries[obj_id] = (net_id, poly)
-            self.dynamic_index.insert(obj_id, poly.bounds)
+            self.dynamic_dilated[obj_id] = dil
+            self.dynamic_index.insert(obj_id, dil.bounds)
 
     def remove_path(self, net_id: str) -> None:
         """
@@ -97,7 +108,8 @@ class CollisionEngine:
         to_remove = [obj_id for obj_id, (nid, _) in self.dynamic_geometries.items() if nid == net_id]
         for obj_id in to_remove:
             nid, poly = self.dynamic_geometries.pop(obj_id)
-            self.dynamic_index.delete(obj_id, poly.bounds)
+            dilated = self.dynamic_dilated.pop(obj_id)
+            self.dynamic_index.delete(obj_id, dilated.bounds)
 
     def lock_net(self, net_id: str) -> None:
         """
@@ -109,7 +121,10 @@ class CollisionEngine:
         to_move = [obj_id for obj_id, (nid, _) in self.dynamic_geometries.items() if nid == net_id]
         for obj_id in to_move:
             nid, poly = self.dynamic_geometries.pop(obj_id)
-            self.dynamic_index.delete(obj_id, poly.bounds)
+            dilated = self.dynamic_dilated.pop(obj_id)
+            self.dynamic_index.delete(obj_id, dilated.bounds)
+            # Re-buffer for static clearance if necessary. 
+            # Note: dynamic is clearance/2, static is clearance.
             self.add_static_obstacle(poly)
 
     def is_collision(
@@ -121,15 +136,6 @@ class CollisionEngine:
             ) -> bool:
         """
         Alias for check_collision(buffer_mode='static') for backward compatibility.
-
-        Args:
-            geometry: Move geometry to check.
-            net_width: Width of the net (unused).
-            start_port: Starting port for safety check.
-            end_port: Ending port for safety check.
-
-        Returns:
-            True if collision detected.
         """
         _ = net_width
         res = self.check_collision(geometry, 'default', buffer_mode='static', start_port=start_port, end_port=end_port)
@@ -138,13 +144,6 @@ class CollisionEngine:
     def count_congestion(self, geometry: Polygon, net_id: str) -> int:
         """
         Alias for check_collision(buffer_mode='congestion') for backward compatibility.
-
-        Args:
-            geometry: Move geometry to check.
-            net_id: Identifier for the net.
-
-        Returns:
-            Number of overlapping nets.
         """
         res = self.check_collision(geometry, net_id, buffer_mode='congestion')
         return int(res)
@@ -156,6 +155,7 @@ class CollisionEngine:
             buffer_mode: Literal['static', 'congestion'] = 'static',
             start_port: Port | None = None,
             end_port: Port | None = None,
+            dilated_geometry: Polygon | None = None,
             ) -> bool | int:
         """
         Check for collisions using unified dilation logic.
@@ -166,17 +166,24 @@ class CollisionEngine:
             buffer_mode: 'static' (full clearance) or 'congestion' (shared).
             start_port: Optional start port for safety zone.
             end_port: Optional end port for safety zone.
+            dilated_geometry: Optional pre-buffered geometry (clearance/2).
 
         Returns:
             Boolean if static, integer count if congestion.
         """
         if buffer_mode == 'static':
-            test_poly = geometry.buffer(self.clearance)
-            candidates = self.static_index.intersection(test_poly.bounds)
+            # Use raw query against pre-dilated obstacles
+            candidates = self.static_index.intersection(geometry.bounds)
 
             for obj_id in candidates:
-                if self.static_prepared[obj_id].intersects(test_poly):
+                if self.static_prepared[obj_id].intersects(geometry):
                     if start_port or end_port:
+                        # Safety zone check: requires intersection of DILATED query and RAW obstacle.
+                        # Always re-buffer here because static check needs full clearance dilation,
+                        # whereas the provided dilated_geometry is usually clearance/2.
+                        dilation = self.clearance
+                        test_poly = geometry.buffer(dilation)
+                        
                         intersection = test_poly.intersection(self.static_geometries[obj_id])
                         if intersection.is_empty:
                             continue
@@ -198,12 +205,12 @@ class CollisionEngine:
 
         # buffer_mode == 'congestion'
         dilation = self.clearance / 2.0
-        test_poly = geometry.buffer(dilation)
+        test_poly = dilated_geometry if dilated_geometry else geometry.buffer(dilation)
         candidates = self.dynamic_index.intersection(test_poly.bounds)
 
         count = 0
         for obj_id in candidates:
-            other_net_id, other_poly = self.dynamic_geometries[obj_id]
-            if other_net_id != net_id and test_poly.intersects(other_poly.buffer(dilation)):
+            other_net_id, _ = self.dynamic_geometries[obj_id]
+            if other_net_id != net_id and test_poly.intersects(self.dynamic_dilated[obj_id]):
                 count += 1
         return count
diff --git a/inire/geometry/components.py b/inire/geometry/components.py
index 595b9dd..e81102d 100644
--- a/inire/geometry/components.py
+++ b/inire/geometry/components.py
@@ -1,14 +1,12 @@
 from __future__ import annotations
 
-from typing import Literal, cast, TYPE_CHECKING, Union, Any
+from typing import Literal, cast
 import numpy
 from shapely.geometry import Polygon, box
 from shapely.ops import unary_union
 
 from .primitives import Port
 
-if TYPE_CHECKING:
-    from collections.abc import Sequence
 
 
 # Search Grid Snap (1.0 µm)
@@ -32,11 +30,14 @@ class ComponentResult:
     """
     The result of a component generation: geometry, final port, and physical length.
     """
-    __slots__ = ('geometry', 'end_port', 'length')
+    __slots__ = ('geometry', 'dilated_geometry', 'end_port', 'length')
 
     geometry: list[Polygon]
     """ List of polygons representing the component geometry """
 
+    dilated_geometry: list[Polygon] | None
+    """ Optional list of pre-dilated polygons for collision optimization """
+
     end_port: Port
     """ The final port after the component """
 
@@ -48,8 +49,10 @@ class ComponentResult:
             geometry: list[Polygon],
             end_port: Port,
             length: float,
+            dilated_geometry: list[Polygon] | None = None,
             ) -> None:
         self.geometry = geometry
+        self.dilated_geometry = dilated_geometry
         self.end_port = end_port
         self.length = length
 
@@ -64,6 +67,7 @@ class Straight:
             length: float,
             width: float,
             snap_to_grid: bool = True,
+            dilation: float = 0.0,
             ) -> ComponentResult:
         """
         Generate a straight waveguide segment.
@@ -73,16 +77,17 @@ class Straight:
             length: Requested length.
             width: Waveguide width.
             snap_to_grid: Whether to snap the end port to the search grid.
+            dilation: Optional dilation distance for pre-calculating collision geometry.
 
         Returns:
             A ComponentResult containing the straight segment.
         """
         rad = numpy.radians(start_port.orientation)
-        dx = length * numpy.cos(rad)
-        dy = length * numpy.sin(rad)
+        cos_val = numpy.cos(rad)
+        sin_val = numpy.sin(rad)
 
-        ex = start_port.x + dx
-        ey = start_port.y + dy
+        ex = start_port.x + length * cos_val
+        ey = start_port.y + length * sin_val
 
         if snap_to_grid:
             ex = snap_search_grid(ex)
@@ -91,21 +96,36 @@ class Straight:
         end_port = Port(ex, ey, start_port.orientation)
         actual_length = numpy.sqrt((end_port.x - start_port.x)**2 + (end_port.y - start_port.y)**2)
 
-        # Create polygon
+        # Create polygons using vectorized points
         half_w = width / 2.0
-        # Points relative to start port (0,0)
-        points = [(0, half_w), (actual_length, half_w), (actual_length, -half_w), (0, -half_w)]
+        pts_raw = numpy.array([
+            [0, half_w], 
+            [actual_length, half_w], 
+            [actual_length, -half_w], 
+            [0, -half_w]
+        ])
+        
+        # Rotation matrix (standard 2D rotation)
+        rot_matrix = numpy.array([[cos_val, -sin_val], [sin_val, cos_val]])
+        
+        # Transform points: P' = R * P + T
+        poly_points = (pts_raw @ rot_matrix.T) + [start_port.x, start_port.y]
+        geom = [Polygon(poly_points)]
 
-        # Transform points
-        cos_val = numpy.cos(rad)
-        sin_val = numpy.sin(rad)
-        poly_points = []
-        for px, py in points:
-            tx = start_port.x + px * cos_val - py * sin_val
-            ty = start_port.y + px * sin_val + py * cos_val
-            poly_points.append((tx, ty))
+        dilated_geom = None
+        if dilation > 0:
+            # Direct calculation of dilated rectangle instead of expensive buffer()
+            half_w_dil = half_w + dilation
+            pts_dil = numpy.array([
+                [-dilation, half_w_dil], 
+                [actual_length + dilation, half_w_dil], 
+                [actual_length + dilation, -half_w_dil], 
+                [-dilation, -half_w_dil]
+            ])
+            poly_points_dil = (pts_dil @ rot_matrix.T) + [start_port.x, start_port.y]
+            dilated_geom = [Polygon(poly_points_dil)]
 
-        return ComponentResult(geometry=[Polygon(poly_points)], end_port=end_port, length=actual_length)
+        return ComponentResult(geometry=geom, end_port=end_port, length=actual_length, dilated_geometry=dilated_geom)
 
 
 def _get_num_segments(radius: float, angle_deg: float, sagitta: float = 0.01) -> int:
@@ -140,7 +160,7 @@ def _get_arc_polygons(
         sagitta: float = 0.01,
         ) -> list[Polygon]:
     """
-    Helper to generate arc-shaped polygons.
+    Helper to generate arc-shaped polygons using vectorized NumPy operations.
 
     Args:
         cx, cy: Center coordinates.
@@ -154,11 +174,20 @@ def _get_arc_polygons(
     """
     num_segments = _get_num_segments(radius, float(numpy.degrees(abs(t_end - t_start))), sagitta)
     angles = numpy.linspace(t_start, t_end, num_segments + 1)
+    
+    cos_a = numpy.cos(angles)
+    sin_a = numpy.sin(angles)
+    
     inner_radius = radius - width / 2.0
     outer_radius = radius + width / 2.0
-    inner_points = [(cx + inner_radius * numpy.cos(a), cy + inner_radius * numpy.sin(a)) for a in angles]
-    outer_points = [(cx + outer_radius * numpy.cos(a), cy + outer_radius * numpy.sin(a)) for a in reversed(angles)]
-    return [Polygon(inner_points + outer_points)]
+    
+    inner_points = numpy.stack([cx + inner_radius * cos_a, cy + inner_radius * sin_a], axis=1)
+    outer_points = numpy.stack([cx + outer_radius * cos_a[::-1], cy + outer_radius * sin_a[::-1]], axis=1)
+    
+    # Concatenate inner and outer points to form the polygon ring
+    poly_points = numpy.concatenate([inner_points, outer_points])
+    
+    return [Polygon(poly_points)]
 
 
 def _clip_bbox(
@@ -291,6 +320,7 @@ class Bend90:
             sagitta: float = 0.01,
             collision_type: Literal["arc", "bbox", "clipped_bbox"] | Polygon = "arc",
             clip_margin: float = 10.0,
+            dilation: float = 0.0,
             ) -> ComponentResult:
         """
         Generate a 90-degree bend.
@@ -303,6 +333,7 @@ class Bend90:
             sagitta: Geometric fidelity.
             collision_type: Collision model.
             clip_margin: Margin for clipped_bbox.
+            dilation: Optional dilation distance for pre-calculating collision geometry.
 
         Returns:
             A ComponentResult containing the bend.
@@ -323,8 +354,15 @@ class Bend90:
         collision_polys = _apply_collision_model(
             arc_polys[0], collision_type, radius, width, cx, cy, clip_margin
         )
+        
+        dilated_geom = [p.buffer(dilation) for p in collision_polys] if dilation > 0 else None
 
-        return ComponentResult(geometry=collision_polys, end_port=end_port, length=radius * numpy.pi / 2.0)
+        return ComponentResult(
+            geometry=collision_polys, 
+            end_port=end_port, 
+            length=radius * numpy.pi / 2.0,
+            dilated_geometry=dilated_geom
+        )
 
 
 class SBend:
@@ -340,6 +378,7 @@ class SBend:
             sagitta: float = 0.01,
             collision_type: Literal["arc", "bbox", "clipped_bbox"] | Polygon = "arc",
             clip_margin: float = 10.0,
+            dilation: float = 0.0,
             ) -> ComponentResult:
         """
         Generate a parametric S-bend (two tangent arcs).
@@ -352,6 +391,7 @@ class SBend:
             sagitta: Geometric fidelity.
             collision_type: Collision model.
             clip_margin: Margin for clipped_bbox.
+            dilation: Optional dilation distance for pre-calculating collision geometry.
 
         Returns:
             A ComponentResult containing the S-bend.
@@ -385,13 +425,22 @@ class SBend:
         arc2 = _get_arc_polygons(cx2, cy2, radius, width, ts2, te2, sagitta)[0]
 
         if collision_type == "clipped_bbox":
-            col1 = _apply_collision_model(arc1, collision_type, radius, width, cx1, cy1, clip_margin)
-            col2 = _apply_collision_model(arc2, collision_type, radius, width, cx2, cy2, clip_margin)
-            collision_polys = [cast('Polygon', unary_union(col1 + col2))]
+            col1 = _apply_collision_model(arc1, collision_type, radius, width, cx1, cy1, clip_margin)[0]
+            col2 = _apply_collision_model(arc2, collision_type, radius, width, cx2, cy2, clip_margin)[0]
+            # Optimization: keep as list instead of unary_union for search efficiency
+            collision_polys = [col1, col2]
         else:
-            combined_arc = cast('Polygon', unary_union([arc1, arc2]))
-            collision_polys = _apply_collision_model(
-                combined_arc, collision_type, radius, width, 0, 0, clip_margin
-            )
+            # For other models, we can either combine or keep separate. 
+            # Keeping separate is generally better for CollisionEngine.
+            col1 = _apply_collision_model(arc1, collision_type, radius, width, cx1, cy1, clip_margin)[0]
+            col2 = _apply_collision_model(arc2, collision_type, radius, width, cx2, cy2, clip_margin)[0]
+            collision_polys = [col1, col2]
 
-        return ComponentResult(geometry=collision_polys, end_port=end_port, length=2 * radius * theta)
+        dilated_geom = [p.buffer(dilation) for p in collision_polys] if dilation > 0 else None
+
+        return ComponentResult(
+            geometry=collision_polys, 
+            end_port=end_port, 
+            length=2 * radius * theta,
+            dilated_geometry=dilated_geom
+        )
diff --git a/inire/router/astar.py b/inire/router/astar.py
index 754049f..74ef3b1 100644
--- a/inire/router/astar.py
+++ b/inire/router/astar.py
@@ -83,7 +83,7 @@ class AStarRouter:
     """
     Hybrid State-Lattice A* Router.
     """
-    __slots__ = ('cost_evaluator', 'config', 'node_limit', 'total_nodes_expanded', '_collision_cache')
+    __slots__ = ('cost_evaluator', 'config', 'node_limit', 'total_nodes_expanded', '_collision_cache', '_self_dilation')
 
     cost_evaluator: CostEvaluator
     """ The evaluator for path and proximity costs """
@@ -100,6 +100,9 @@ class AStarRouter:
     _collision_cache: dict[tuple[float, float, float, str, float, str], bool]
     """ Internal cache for move collision checks """
 
+    _self_dilation: float
+    """ Cached dilation value for collision checks (clearance / 2.0) """
+
     def __init__(
             self,
             cost_evaluator: CostEvaluator,
@@ -146,6 +149,7 @@ class AStarRouter:
         self.node_limit = self.config.node_limit
         self.total_nodes_expanded = 0
         self._collision_cache = {}
+        self._self_dilation = self.cost_evaluator.collision_engine.clearance / 2.0
 
     def route(
             self,
@@ -226,7 +230,7 @@ class AStarRouter:
                 proj = dx * numpy.cos(rad) + dy * numpy.sin(rad)
                 perp = -dx * numpy.sin(rad) + dy * numpy.cos(rad)
                 if proj > 0 and abs(perp) < 1e-6:
-                    res = Straight.generate(current.port, proj, net_width, snap_to_grid=False)
+                    res = Straight.generate(current.port, proj, net_width, snap_to_grid=False, dilation=self._self_dilation)
                     self._add_node(current, res, target, net_width, net_id, open_set, closed_set, 'SnapStraight')
 
             # B. Try SBend exact reach
@@ -245,7 +249,8 @@ class AStarRouter:
                                 radius,
                                 net_width,
                                 collision_type=self.config.bend_collision_type,
-                                clip_margin=self.config.bend_clip_margin
+                                clip_margin=self.config.bend_clip_margin,
+                                dilation=self._self_dilation
                             )
                             self._add_node(current, res, target, net_width, net_id, open_set, closed_set, 'SnapSBend', move_radius=radius)
                         except ValueError:
@@ -258,7 +263,7 @@ class AStarRouter:
              lengths = sorted(set(lengths + fine_steps))
 
         for length in lengths:
-            res = Straight.generate(current.port, length, net_width)
+            res = Straight.generate(current.port, length, net_width, dilation=self._self_dilation)
             self._add_node(current, res, target, net_width, net_id, open_set, closed_set, f'S{length}')
 
         # 3. Lattice Bends
@@ -270,7 +275,8 @@ class AStarRouter:
                     net_width,
                     direction,
                     collision_type=self.config.bend_collision_type,
-                    clip_margin=self.config.bend_clip_margin
+                    clip_margin=self.config.bend_clip_margin,
+                    dilation=self._self_dilation
                 )
                 self._add_node(current, res, target, net_width, net_id, open_set, closed_set, f'B{radius}{direction}', move_radius=radius)
 
@@ -284,7 +290,8 @@ class AStarRouter:
                         radius,
                         net_width,
                         collision_type=self.config.bend_collision_type,
-                        clip_margin=self.config.bend_clip_margin
+                        clip_margin=self.config.bend_clip_margin,
+                        dilation=self._self_dilation
                     )
                     self._add_node(current, res, target, net_width, net_id, open_set, closed_set, f'SB{offset}R{radius}', move_radius=radius)
                 except ValueError:
@@ -320,9 +327,11 @@ class AStarRouter:
                 return
         else:
             hard_coll = False
-            for poly in result.geometry:
+            for i, poly in enumerate(result.geometry):
+                dil_poly = result.dilated_geometry[i] if result.dilated_geometry else None
                 if self.cost_evaluator.collision_engine.check_collision(
-                    poly, net_id, buffer_mode='static', start_port=parent.port, end_port=result.end_port
+                    poly, net_id, buffer_mode='static', start_port=parent.port, end_port=result.end_port,
+                    dilated_geometry=dil_poly
                 ):
                     hard_coll = True
                     break
@@ -331,27 +340,37 @@ class AStarRouter:
                 return
 
         # 3. Check for Self-Intersection (Limited to last 100 segments for performance)
-        dilation = self.cost_evaluator.collision_engine.clearance / 2.0
-        for move_poly in result.geometry:
-            dilated_move = move_poly.buffer(dilation)
-            curr_p: AStarNode | None = parent
-            seg_idx = 0
-            while curr_p and curr_p.component_result and seg_idx < 100:
-                if seg_idx > 0:
-                    for prev_poly in curr_p.component_result.geometry:
-                        if dilated_move.bounds[0] > prev_poly.bounds[2] + dilation or \
-                           dilated_move.bounds[2] < prev_poly.bounds[0] - dilation or \
-                           dilated_move.bounds[1] > prev_poly.bounds[3] + dilation or \
-                           dilated_move.bounds[3] < prev_poly.bounds[1] - dilation:
-                            continue
+        # Optimization: use pre-dilated geometries
+        if result.dilated_geometry:
+            for dilated_move in result.dilated_geometry:
+                curr_p: AStarNode | None = parent
+                seg_idx = 0
+                while curr_p and curr_p.component_result and seg_idx < 100:
+                    if seg_idx > 0:
+                        res_p = curr_p.component_result
+                        if res_p.dilated_geometry:
+                            for dilated_prev in res_p.dilated_geometry:
+                                if (dilated_move.bounds[0] > dilated_prev.bounds[2] or
+                                    dilated_move.bounds[2] < dilated_prev.bounds[0] or
+                                    dilated_move.bounds[1] > dilated_prev.bounds[3] or
+                                    dilated_move.bounds[3] < dilated_prev.bounds[1]):
+                                    continue
 
-                        dilated_prev = prev_poly.buffer(dilation)
-                        if dilated_move.intersects(dilated_prev):
-                            overlap = dilated_move.intersection(dilated_prev)
-                            if overlap.area > 1e-6:
-                                return
-                curr_p = curr_p.parent
-                seg_idx += 1
+                                if dilated_move.intersects(dilated_prev):
+                                    overlap = dilated_move.intersection(dilated_prev)
+                                    if overlap.area > 1e-6:
+                                        return
+                        else:
+                            # Fallback if no pre-dilation (should not happen with new logic)
+                            dilation = self._self_dilation
+                            for prev_poly in res_p.geometry:
+                                dilated_prev = prev_poly.buffer(dilation)
+                                if dilated_move.intersects(dilated_prev):
+                                    overlap = dilated_move.intersection(dilated_prev)
+                                    if overlap.area > 1e-6:
+                                        return
+                    curr_p = curr_p.parent
+                    seg_idx += 1
 
         move_cost = self.cost_evaluator.evaluate_move(
             result.geometry,
@@ -359,7 +378,8 @@ class AStarRouter:
             net_width,
             net_id,
             start_port=parent.port,
-            length=result.length
+            length=result.length,
+            dilated_geometry=result.dilated_geometry
         )
 
         if move_cost > 1e12:
diff --git a/inire/router/cost.py b/inire/router/cost.py
index 6b2ff54..1753aa9 100644
--- a/inire/router/cost.py
+++ b/inire/router/cost.py
@@ -103,6 +103,7 @@ class CostEvaluator:
             net_id: str,
             start_port: Port | None = None,
             length: float = 0.0,
+            dilated_geometry: list[Polygon] | None = None,
             ) -> float:
         """
         Calculate the cost of a single move (Straight, Bend, SBend).
@@ -114,6 +115,7 @@ class CostEvaluator:
             net_id: Identifier for the net.
             start_port: Port at the start of the move.
             length: Physical path length of the move.
+            dilated_geometry: Pre-calculated dilated polygons.
 
         Returns:
             Total cost of the move, or 1e15 if invalid.
@@ -126,15 +128,19 @@ class CostEvaluator:
             return 1e15
 
         # 2. Collision Check
-        for poly in geometry:
+        for i, poly in enumerate(geometry):
+            dil_poly = dilated_geometry[i] if dilated_geometry else None
             # Hard Collision (Static obstacles)
             if self.collision_engine.check_collision(
-                poly, net_id, buffer_mode='static', start_port=start_port, end_port=end_port
+                poly, net_id, buffer_mode='static', start_port=start_port, end_port=end_port,
+                dilated_geometry=dil_poly
             ):
                 return 1e15
 
             # Soft Collision (Negotiated Congestion)
-            overlaps = self.collision_engine.check_collision(poly, net_id, buffer_mode='congestion')
+            overlaps = self.collision_engine.check_collision(
+                poly, net_id, buffer_mode='congestion', dilated_geometry=dil_poly
+            )
             if isinstance(overlaps, int) and overlaps > 0:
                 total_cost += overlaps * self.congestion_penalty
 
diff --git a/inire/router/pathfinder.py b/inire/router/pathfinder.py
index 05235b7..40ce644 100644
--- a/inire/router/pathfinder.py
+++ b/inire/router/pathfinder.py
@@ -118,15 +118,23 @@ class PathFinder:
                 if path:
                     # 3. Add to index
                     all_geoms = []
+                    all_dilated = []
                     for res in path:
                         all_geoms.extend(res.geometry)
-                    self.cost_evaluator.collision_engine.add_path(net_id, all_geoms)
+                        if res.dilated_geometry:
+                            all_dilated.extend(res.dilated_geometry)
+                        else:
+                            # Fallback dilation
+                            dilation = self.cost_evaluator.collision_engine.clearance / 2.0
+                            all_dilated.extend([p.buffer(dilation) for p in res.geometry])
+                            
+                    self.cost_evaluator.collision_engine.add_path(net_id, all_geoms, dilated_geometry=all_dilated)
 
                     # Check if this new path has any congestion
                     collision_count = 0
-                    for poly in all_geoms:
+                    for i, poly in enumerate(all_geoms):
                         overlaps = self.cost_evaluator.collision_engine.check_collision(
-                            poly, net_id, buffer_mode='congestion'
+                            poly, net_id, buffer_mode='congestion', dilated_geometry=all_dilated[i]
                         )
                         if isinstance(overlaps, int):
                             collision_count += overlaps
@@ -172,9 +180,10 @@ class PathFinder:
 
             collision_count = 0
             for comp in res.path:
-                for poly in comp.geometry:
+                for i, poly in enumerate(comp.geometry):
+                    dil_poly = comp.dilated_geometry[i] if comp.dilated_geometry else None
                     overlaps = self.cost_evaluator.collision_engine.check_collision(
-                        poly, net_id, buffer_mode='congestion'
+                        poly, net_id, buffer_mode='congestion', dilated_geometry=dil_poly
                     )
                     if isinstance(overlaps, int):
                         collision_count += overlaps
diff --git a/inire/tests/test_components.py b/inire/tests/test_components.py
index 3ce6b18..13bfb56 100644
--- a/inire/tests/test_components.py
+++ b/inire/tests/test_components.py
@@ -50,7 +50,7 @@ def test_sbend_generation() -> None:
     result = SBend.generate(start, offset, radius, width)
     assert result.end_port.y == 5.0
     assert result.end_port.orientation == 0.0
-    assert len(result.geometry) == 1 # Now uses unary_union
+    assert len(result.geometry) == 2 # Optimization: returns individual arcs
 
     # Verify failure for large offset
     with pytest.raises(ValueError, match=r"SBend offset .* must be less than 2\*radius"):
@@ -85,11 +85,13 @@ def test_sbend_collision_models() -> None:
     width = 2.0
 
     res_bbox = SBend.generate(start, offset, radius, width, collision_type="bbox")
-    # Geometry should be a single bounding box polygon
-    assert len(res_bbox.geometry) == 1
+    # Geometry should be a list of individual bbox polygons for each arc
+    assert len(res_bbox.geometry) == 2
 
     res_arc = SBend.generate(start, offset, radius, width, collision_type="arc")
-    assert res_bbox.geometry[0].area > res_arc.geometry[0].area
+    area_bbox = sum(p.area for p in res_bbox.geometry)
+    area_arc = sum(p.area for p in res_arc.geometry)
+    assert area_bbox > area_arc
 
 
 def test_sbend_continuity() -> None:
@@ -107,9 +109,10 @@ def test_sbend_continuity() -> None:
     # For a port at 90 deg, +offset is a shift in -x direction
     assert abs(res.end_port.x - (10.0 - offset)) < 1e-6
 
-    # Geometry should be connected (unary_union results in 1 polygon)
-    assert len(res.geometry) == 1
-    assert res.geometry[0].is_valid
+    # Geometry should be a list of valid polygons
+    assert len(res.geometry) == 2
+    for p in res.geometry:
+        assert p.is_valid
 
 
 def test_arc_sagitta_precision() -> None: