diff --git a/src/ai/api/ai_bridge.hpp b/src/ai/api/ai_bridge.hpp
index 819242e79b..a4bac67f78 100644
--- a/src/ai/api/ai_bridge.hpp
+++ b/src/ai/api/ai_bridge.hpp
@@ -60,10 +60,13 @@ public:
 	static char *GetName(BridgeID bridge_id);
 
 	/**
-	 * Get the maximum speed of a bridge (in km/h).
+	 * Get the maximum speed of a bridge.
 	 * @param bridge_id The bridge to get the maximum speed of.
 	 * @pre IsValidBridge(bridge_id).
 	 * @return The maximum speed the bridge has.
+	 * @note The speed is in OpenTTD's internal speed unit.
+	 *       This is mph / 1.6, which is roughly km/h.
+	 *       To get km/h multiply this number by 1.00584.
 	 */
 	static int32 GetMaxSpeed(BridgeID bridge_id);
 
diff --git a/src/ai/api/ai_engine.hpp b/src/ai/api/ai_engine.hpp
index 7e49558a19..6fe8653274 100644
--- a/src/ai/api/ai_engine.hpp
+++ b/src/ai/api/ai_engine.hpp
@@ -91,7 +91,9 @@ public:
 	 * @param engine_id The engine to get the maximum speed of.
 	 * @pre IsValidEngine(engine_id).
 	 * @return The maximum speed the engine has.
-	 * @note The speed is in km/h.
+	 * @note The speed is in OpenTTD's internal speed unit.
+	 *       This is mph / 1.6, which is roughly km/h.
+	 *       To get km/h multiply this number by 1.00584.
 	 */
 	static int32 GetMaxSpeed(EngineID engine_id);
 
diff --git a/src/ai/api/ai_event_types.hpp b/src/ai/api/ai_event_types.hpp
index 75bef42a1a..044892ab73 100644
--- a/src/ai/api/ai_event_types.hpp
+++ b/src/ai/api/ai_event_types.hpp
@@ -240,7 +240,9 @@ public:
 	/**
 	 * Get the maximum speed of the offered engine.
 	 * @return The maximum speed the engine has.
-	 * @note The speed is in km/h.
+	 * @note The speed is in OpenTTD's internal speed unit.
+	 *       This is mph / 1.6, which is roughly km/h.
+	 *       To get km/h multiply this number by 1.00584.
 	 */
 	int32 GetMaxSpeed();
 
diff --git a/src/ai/api/ai_vehicle.cpp b/src/ai/api/ai_vehicle.cpp
index 93732130b2..081b7b7398 100644
--- a/src/ai/api/ai_vehicle.cpp
+++ b/src/ai/api/ai_vehicle.cpp
@@ -278,7 +278,7 @@
 {
 	if (!IsValidVehicle(vehicle_id)) return -1;
 
-	return ::GetVehicle(vehicle_id)->GetDisplaySpeed();
+	return ::GetVehicle(vehicle_id)->GetDisplaySpeed() * 16 / 10;
 }
 
 /* static */ AIVehicle::VehicleState AIVehicle::GetState(VehicleID vehicle_id)
diff --git a/src/ai/api/ai_vehicle.hpp b/src/ai/api/ai_vehicle.hpp
index f0be433da9..961a451d3e 100644
--- a/src/ai/api/ai_vehicle.hpp
+++ b/src/ai/api/ai_vehicle.hpp
@@ -205,7 +205,9 @@ public:
 	 * @param vehicle_id The vehicle to get the age of.
 	 * @pre IsValidVehicle(vehicle_id).
 	 * @return The current speed of the vehicle.
-	 * @note Speed is in km/h.
+	 * @note The speed is in OpenTTD's internal speed unit.
+	 *       This is mph / 1.6, which is roughly km/h.
+	 *       To get km/h multiply this number by 1.00584.
 	 */
 	static int32 GetCurrentSpeed(VehicleID vehicle_id);