diff --git a/OpenRA.Mods.Common/OpenRA.Mods.Common.csproj b/OpenRA.Mods.Common/OpenRA.Mods.Common.csproj
index 5a48825910..b7545db6da 100644
--- a/OpenRA.Mods.Common/OpenRA.Mods.Common.csproj
+++ b/OpenRA.Mods.Common/OpenRA.Mods.Common.csproj
@@ -484,7 +484,6 @@
     <Compile Include="Traits\ThrowsParticle.cs" />
     <Compile Include="Traits\Tooltip.cs" />
     <Compile Include="Traits\TransformOnCapture.cs" />
-    <Compile Include="Traits\TransformOnPassenger.cs" />
     <Compile Include="Traits\Transforms.cs" />
     <Compile Include="Traits\Turreted.cs" />
     <Compile Include="Traits\ProducibleWithLevel.cs" />
diff --git a/OpenRA.Mods.Common/Traits/TransformOnPassenger.cs b/OpenRA.Mods.Common/Traits/TransformOnPassenger.cs
deleted file mode 100644
index 5fb040115b..0000000000
--- a/OpenRA.Mods.Common/Traits/TransformOnPassenger.cs
+++ /dev/null
@@ -1,55 +0,0 @@
-#region Copyright & License Information
-/*
- * Copyright 2007-2015 The OpenRA Developers (see AUTHORS)
- * This file is part of OpenRA, which is free software. It is made
- * available to you under the terms of the GNU General Public License
- * as published by the Free Software Foundation. For more information,
- * see COPYING.
- */
-#endregion
-
-using System.Collections.Generic;
-using System.Linq;
-using OpenRA.Mods.Common.Activities;
-using OpenRA.Traits;
-
-namespace OpenRA.Mods.Common.Traits
-{
-	public class TransformOnPassengerInfo : ITraitInfo
-	{
-		[ActorReference, FieldLoader.Require] public readonly HashSet<string> PassengerTypes = new HashSet<string>();
-		[ActorReference] public readonly string OnEnter = null;
-		[ActorReference] public readonly string OnExit = null;
-		public readonly bool SkipMakeAnims = false;
-		public readonly bool BecomeNeutral = false;
-
-		public object Create(ActorInitializer init) { return new TransformOnPassenger(this); }
-	}
-
-	public class TransformOnPassenger : INotifyPassengerEntered, INotifyPassengerExited
-	{
-		readonly TransformOnPassengerInfo info;
-
-		public TransformOnPassenger(TransformOnPassengerInfo info) { this.info = info; }
-
-		void MaybeTransform(Actor self, Actor passenger, string transformTo)
-		{
-			if (info.PassengerTypes.Contains(passenger.Info.Name) && transformTo != null)
-			{
-				self.World.AddFrameEndTask(w =>
-				{
-					var facing = self.TraitOrDefault<IFacing>();
-					var transform = new Transform(self, transformTo) { SkipMakeAnims = info.SkipMakeAnims };
-					if (facing != null) transform.Facing = facing.Facing;
-
-					self.CancelActivity();
-					self.QueueActivity(transform);
-					if (info.BecomeNeutral) self.ChangeOwner(self.World.WorldActor.Owner);
-				});
-			}
-		}
-
-		public void PassengerEntered(Actor self, Actor passenger) { MaybeTransform(self, passenger, info.OnEnter); }
-		public void PassengerExited(Actor self, Actor passenger) { MaybeTransform(self, passenger, info.OnExit); }
-	}
-}
diff --git a/OpenRA.Mods.Common/UtilityCommands/UpgradeRules.cs b/OpenRA.Mods.Common/UtilityCommands/UpgradeRules.cs
index 0e49de27fd..595a0e11b1 100644
--- a/OpenRA.Mods.Common/UtilityCommands/UpgradeRules.cs
+++ b/OpenRA.Mods.Common/UtilityCommands/UpgradeRules.cs
@@ -2807,6 +2807,14 @@ namespace OpenRA.Mods.Common.UtilityCommands
 					}
 				}
 
+				// Remove obsolete TransformOnPassenger trait.
+				if (engineVersion < 20160102)
+				{
+					node.Value.Nodes.RemoveAll(x => x.Key.Contains("TransformOnPassenger"));
+					Console.WriteLine("TransformOnPassenger has been removed.");
+					Console.WriteLine("Use the upgrades system to apply modifiers to the transport actor instead.");
+				}
+
 				UpgradeActorRules(engineVersion, ref node.Value.Nodes, node, depth + 1);
 			}
 		}