diff --git a/validate_yaml.py b/validate_yaml.py
index db2c6b0..0fc82ab 100755
--- a/validate_yaml.py
+++ b/validate_yaml.py
@@ -385,9 +385,39 @@ def check_ferries() -> None:
     print(len(ferries), "ferries")
 
 
+def check_buses() -> None:
+    """Check buses and ensure no bus journey exceeds 12 hours."""
+    buses = agenda.travel.parse_yaml("buses", data_dir)
+    max_duration = timedelta(hours=12)
+
+    for bus in buses:
+        depart = normalize_datetime(bus["depart"])
+        arrive = normalize_datetime(bus["arrive"])
+
+        if arrive < depart:
+            print("Invalid bus journey found (arrive before depart):")
+            print(f"  {bus.get('depart')} {bus.get('from', '')} -> {bus.get('to', '')}")
+            print(f"  arrive: {bus.get('arrive')}")
+            assert False, "Bus journey arrival time is earlier than departure time."
+
+        duration = arrive - depart
+        if duration > max_duration:
+            print("Overlong bus journey found:")
+            print(f"  {bus.get('depart')} {bus.get('from', '')} -> {bus.get('to', '')}")
+            print(f"  arrive: {bus.get('arrive')}")
+            print(f"  duration: {duration}")
+            assert False, "Bus journey is longer than 12 hours."
+
+        check_currency(bus)
+
+    print(len(buses), "buses")
+
+
 def check_airlines() -> list[agenda.types.StrDict]:
     """Check airlines."""
-    airlines = agenda.travel.parse_yaml("airlines", data_dir)
+    airlines = typing.cast(
+        list[agenda.types.StrDict], agenda.travel.parse_yaml("airlines", data_dir)
+    )
     print(len(airlines), "airlines")
     for airline in airlines:
         try:
@@ -414,6 +444,7 @@ def check() -> None:
     check_flights({airline["iata"] for airline in airlines})
     check_trains()
     check_ferries()
+    check_buses()
     check_conferences()
     check_events()
     check_accommodation()