--- a/src/engine_type.h
+++ b/src/engine_type.h
@@ -19,24 +19,27 @@
 #include "sound_type.h"
 #include "strings_type.h"
 
-typedef uint16 EngineID;
+typedef uint16 EngineID; ///< Unique identification number of an engine.
 
 struct Engine;
 
+/** Available types of rail vehicles. */
 enum RailVehicleTypes {
 	RAILVEH_SINGLEHEAD,  ///< indicates a "standalone" locomotive
 	RAILVEH_MULTIHEAD,   ///< indicates a combination of two locomotives
 	RAILVEH_WAGON,       ///< simple wagon, not motorized
 };
 
+/** Type of rail engine. */
 enum EngineClass {
-	EC_STEAM,
-	EC_DIESEL,
-	EC_ELECTRIC,
-	EC_MONORAIL,
-	EC_MAGLEV,
+	EC_STEAM,    ///< Steam rail engine.
+	EC_DIESEL,   ///< Diesel rail engine.
+	EC_ELECTRIC, ///< Electric rail engine.
+	EC_MONORAIL, ///< Mono rail engine.
+	EC_MAGLEV,   ///< Maglev engine.
 };
 
+/** Information about a rail vehicle. */
 struct RailVehicleInfo {
 	byte image_index;
 	RailVehicleTypes railveh_type;
@@ -59,6 +62,7 @@
 	byte user_def_data;             ///< Property 0x25: "User-defined bit mask" Used only for (very few) NewGRF vehicles
 };
 
+/** Information about a ship vehicle. */
 struct ShipVehicleInfo {
 	byte image_index;
 	byte cost_factor;
@@ -70,15 +74,18 @@
 	byte visual_effect;    ///< Bitstuffed NewGRF visual effect data
 };
 
-/* AircraftVehicleInfo subtypes, bitmask type.
+/**
+ * AircraftVehicleInfo subtypes, bitmask type.
  * If bit 0 is 0 then it is a helicopter, otherwise it is a plane
- * in which case bit 1 tells us whether it's a big(fast) plane or not */
+ * in which case bit 1 tells us whether it's a big(fast) plane or not.
+ */
 enum AircraftSubTypeBits {
 	AIR_HELI = 0,
 	AIR_CTOL = 1, ///< Conventional Take Off and Landing, i.e. planes
 	AIR_FAST = 2
 };
 
+/** Information about a aircraft vehicle. */
 struct AircraftVehicleInfo {
 	byte image_index;
 	byte cost_factor;
@@ -91,6 +98,7 @@
 	uint16 passenger_capacity;
 };
 
+/** Information about a road vehicle. */
 struct RoadVehicleInfo {
 	byte image_index;
 	byte cost_factor;
@@ -150,6 +158,6 @@
 static const uint MAX_LENGTH_ENGINE_NAME_CHARS  =  32; ///< The maximum length of an engine name in characters including '\0'
 static const uint MAX_LENGTH_ENGINE_NAME_PIXELS = 160; ///< The maximum length of an engine name in pixels
 
-static const EngineID INVALID_ENGINE = 0xFFFF;
+static const EngineID INVALID_ENGINE = 0xFFFF; ///< Constant denoting an invalid engine.
 
 #endif /* ENGINE_TYPE_H */