diff --git a/SRT/passenger.py b/SRT/passenger.py
index f661c64..dfa6bb0 100644
--- a/SRT/passenger.py
+++ b/SRT/passenger.py
@@ -22,11 +22,16 @@ def __repr__(self):
         return f"{self.name} {self.count}명"
 
     def __add__(self, other: "Passenger") -> "Passenger":
-        assert isinstance(other, self.__class__)
+        if not isinstance(other, self.__class__):
+            raise TypeError("Passenger types must be the same")
+        
         if self.type_code == other.type_code:
             new_count = self.count + other.count
             return self.__class__(count=new_count)
 
+        raise ValueError("Passenger types must be the same")
+    
+
     @classmethod
     def combine(cls, passengers: list["Passenger"]) -> list["Passenger"]:
         if list(filter(lambda x: not isinstance(x, Passenger), passengers)):