--- a/src/effectvehicle.cpp
+++ b/src/effectvehicle.cpp
@@ -531,30 +531,32 @@
 typedef void EffectInitProc(EffectVehicle *v);
 typedef bool EffectTickProc(EffectVehicle *v);
 
+/** Functions to initialise an effect vehicle after construction. */
 static EffectInitProc * const _effect_init_procs[] = {
-	ChimneySmokeInit,
-	SteamSmokeInit,
-	DieselSmokeInit,
-	ElectricSparkInit,
-	SmokeInit,
-	ExplosionLargeInit,
-	BreakdownSmokeInit,
-	ExplosionSmallInit,
-	BulldozerInit,
-	BubbleInit,
+	ChimneySmokeInit,   // EV_CHIMNEY_SMOKE
+	SteamSmokeInit,     // EV_STEAM_SMOKE
+	DieselSmokeInit,    // EV_DIESEL_SMOKE
+	ElectricSparkInit,  // EV_ELECTRIC_SPARK
+	SmokeInit,          // EV_SMOKE
+	ExplosionLargeInit, // EV_EXPLOSION_LARGE
+	BreakdownSmokeInit, // EV_BREAKDOWN_SMOKE
+	ExplosionSmallInit, // EV_EXPLOSION_SMALL
+	BulldozerInit,      // EV_BULLDOZER
+	BubbleInit,         // EV_BUBBLE
 };
 
+/** Functions for controling effect vehicles at each tick. */
 static EffectTickProc * const _effect_tick_procs[] = {
-	ChimneySmokeTick,
-	SteamSmokeTick,
-	DieselSmokeTick,
-	ElectricSparkTick,
-	SmokeTick,
-	ExplosionLargeTick,
-	BreakdownSmokeTick,
-	ExplosionSmallTick,
-	BulldozerTick,
-	BubbleTick,
+	ChimneySmokeTick,   // EV_CHIMNEY_SMOKE
+	SteamSmokeTick,     // EV_STEAM_SMOKE
+	DieselSmokeTick,    // EV_DIESEL_SMOKE
+	ElectricSparkTick,  // EV_ELECTRIC_SPARK
+	SmokeTick,          // EV_SMOKE
+	ExplosionLargeTick, // EV_EXPLOSION_LARGE
+	BreakdownSmokeTick, // EV_BREAKDOWN_SMOKE
+	ExplosionSmallTick, // EV_EXPLOSION_SMALL
+	BulldozerTick,      // EV_BULLDOZER
+	BubbleTick,         // EV_BUBBLE
 };
 
 

--- a/src/effectvehicle_func.h
+++ b/src/effectvehicle_func.h
@@ -16,16 +16,16 @@
 
 /** Effect vehicle types */
 enum EffectVehicleType {
-	EV_CHIMNEY_SMOKE   = 0,
-	EV_STEAM_SMOKE     = 1,
-	EV_DIESEL_SMOKE    = 2,
-	EV_ELECTRIC_SPARK  = 3,
-	EV_SMOKE           = 4,
-	EV_EXPLOSION_LARGE = 5,
-	EV_BREAKDOWN_SMOKE = 6,
-	EV_EXPLOSION_SMALL = 7,
-	EV_BULLDOZER       = 8,
-	EV_BUBBLE          = 9
+	EV_CHIMNEY_SMOKE            =  0, ///< Smoke of power plant (industry).
+	EV_STEAM_SMOKE              =  1, ///< Smoke of steam engines.
+	EV_DIESEL_SMOKE             =  2, ///< Smoke of diesel engines.
+	EV_ELECTRIC_SPARK           =  3, ///< Sparcs of electric engines.
+	EV_SMOKE                    =  4, ///< Smoke of broken aircraft, copper mine and disasters.
+	EV_EXPLOSION_LARGE          =  5, ///< Various explosions.
+	EV_BREAKDOWN_SMOKE          =  6, ///< Smoke of broken vehicles except aircraft.
+	EV_EXPLOSION_SMALL          =  7, ///< Various explosions.
+	EV_BULLDOZER                =  8, ///< Bulldozer at roadworks.
+	EV_BUBBLE                   =  9, ///< Bubble of bubble generator (industry).
 };
 
 EffectVehicle *CreateEffectVehicle(int x, int y, int z, EffectVehicleType type);