diff --git a/simulator/simple_planning_simulator/src/simple_planning_simulator/simple_planning_simulator_core.cpp b/simulator/simple_planning_simulator/src/simple_planning_simulator/simple_planning_simulator_core.cpp
index 80f0722824d93..7d09aabdc9abd 100644
--- a/simulator/simple_planning_simulator/src/simple_planning_simulator/simple_planning_simulator_core.cpp
+++ b/simulator/simple_planning_simulator/src/simple_planning_simulator/simple_planning_simulator_core.cpp
@@ -489,7 +489,7 @@ void SimplePlanningSimulator::set_input(const Control & cmd, const double acc_by
     if (gear == GearCommand::NONE) {
       return 0.0;
     } else if (gear == GearCommand::REVERSE || gear == GearCommand::REVERSE_2) {
-      return -acc_by_cmd - acc_by_slope;
+      return -acc_by_cmd + acc_by_slope;
     } else {
       return acc_by_cmd + acc_by_slope;
     }