diff --git a/modules/planning/common/obstacle.cc b/modules/planning/common/obstacle.cc
index 9eac16cd0963c6fe28430b6c7d775ad06a69f84b..6d5dcd5b1468cbad42ab0590d30ceef603bd0d81 100644
--- a/modules/planning/common/obstacle.cc
+++ b/modules/planning/common/obstacle.cc
@@ -90,7 +90,7 @@ Obstacle::Obstacle(const std::string& id,
       << perception_obstacle.DebugString();
 
   is_static_ = (is_static || obstacle_priority == ObstaclePriority::IGNORE);
-  is_virtual_ = IsVirtualObstacle(perception_obstacle);
+  is_virtual_ = (perception_obstacle.id() < 0);
   speed_ = std::hypot(perception_obstacle.velocity().x(),
                       perception_obstacle.velocity().y());
 }
diff --git a/modules/planning/common/obstacle.h b/modules/planning/common/obstacle.h
index 5dc3904f02d1715d23757b60c46aedab0f60475b..516381640915a7e7445030f624e679071879d4cd 100644
--- a/modules/planning/common/obstacle.h
+++ b/modules/planning/common/obstacle.h
@@ -119,11 +119,6 @@ class Obstacle {
   static std::unique_ptr<Obstacle> CreateStaticVirtualObstacles(
       const std::string& id, const common::math::Box2d& obstacle_box);
 
-  static bool IsVirtualObstacle(
-      const perception::PerceptionObstacle& perception_obstacle) {
-    return perception_obstacle.id() < 0;
-  }
-
   static bool IsValidPerceptionObstacle(
       const perception::PerceptionObstacle& obstacle);
 
diff --git a/modules/planning/common/obstacle_test.cc b/modules/planning/common/obstacle_test.cc
index bbc8236d5d7db56d4e670c5b056cc6f99b6058ea..038651b31118b44385f63ed8e38620f825c068d6 100644
--- a/modules/planning/common/obstacle_test.cc
+++ b/modules/planning/common/obstacle_test.cc
@@ -187,7 +187,7 @@ TEST(Obstacle, CreateStaticVirtualObstacle) {
       Obstacle::CreateStaticVirtualObstacles("abc", box);
   EXPECT_EQ("abc", obstacle->Id());
   EXPECT_EQ(-314721735, obstacle->PerceptionId());
-  EXPECT_TRUE(Obstacle::IsVirtualObstacle(obstacle->Perception()));
+  EXPECT_TRUE(obstacle->IsVirtual());
   auto& perception_box = obstacle->PerceptionBoundingBox();
   EXPECT_DOUBLE_EQ(0.0, perception_box.center().x());
   EXPECT_DOUBLE_EQ(0.0, perception_box.center().y());
diff --git a/modules/planning/toolkits/optimizers/road_graph/trajectory_cost.cc b/modules/planning/toolkits/optimizers/road_graph/trajectory_cost.cc
index c804e9037c8e4e8d75a6e456ce3140e825e9a44b..5ad24bca80dbaf7bb23e5db706d46691802f22b7 100644
--- a/modules/planning/toolkits/optimizers/road_graph/trajectory_cost.cc
+++ b/modules/planning/toolkits/optimizers/road_graph/trajectory_cost.cc
@@ -83,7 +83,7 @@ TrajectoryCost::TrajectoryCost(const DpPolyPathConfig &config,
          ptr_obstacle->Perception().type() ==
              perception::PerceptionObstacle::PEDESTRIAN);
 
-    if (Obstacle::IsVirtualObstacle(ptr_obstacle->Perception())) {
+    if (ptr_obstacle->IsVirtual()) {
       // Virtual obstacle
       continue;
     } else if (ptr_obstacle->IsStatic() || is_bycycle_or_pedestrian) {