OTTD's class-specific periodic tile processing routine is called once every +256 ticks for each tile.
 
  | Class | Meaning & details of encoding | 
|---|
  
   | 0 | 
     m5 bits 4..0: tile type:
      
       | 00 | bare land |  | 01 | 1/3 grass |  | 02 | 2/3 grass |  | 03 | full grass |  | 07 | rough land |  | 0B | rocks |  | 0F | fields; type of fields in m3 bits 3..0 (legal values: 0 through 9) m2: Index into the array of industries (farms), INVALID_INDUSTRY (0xFFFF) if farm has been removed
 |  | 10 | 1/4 snow |  | 11 | 2/4 snow |  | 12 | 3/4 snow |  | 13 | full snow |  | 15 | partial desert |  | 17 | full desert | m5 bits 7..5: update counter, incremented on every periodic processing for tile types,
         other than 03, 07, 0B, 10 and above.on wraparound, the tile is updated (for fields, the type of fields in m3 is increased, for other types the tile type in m5 is increased).
 For snow and desert, these bits are not used, tile is updated on every periodic processing.
m1: owner of the tile (normally 10)m4 bits 7..5: type of hedge on the SW border of the tile (1 through 6, or 0=none); bits 4..2: same for the SE border | 
  
   | 1 | 
     m5 bit 7 clear: railway track
      
       m5 bits 0..5: track layout: bit set = track present:
        
         | bit 0: | in the X direction |  | bit 1: | in the Y direction |  | bit 2: | in the north corner (direction W-E) |  | bit 3: | in the south corner (direction W-E) |  | bit 4: | in the west corner (direction N-S) |  | bit 5: | in the east corner (direction N-S) | m5 bit 6 set = with signals:
        
         m3 bits 7..4: bit set = signal present:
          
           For track in the X direction:
            
             | bit 6: | signal in the SW direction |  | bit 7: | signal in the NE direction | For track in the Y direction:
            
             | bit 6: | signal in the NW direction |  | bit 7: | signal in the SE direction | For tracks in the W-E direction:
            
             | bit 4: | signal in the W direction on the track in the S corner |  | bit 5: | signal in the E direction on the track in the S corner |  | bit 6: | signal in the W direction on the track in the N corner |  | bit 7: | signal in the E direction on the track in the N corner | For tracks in the N-S direction:
            
             | bit 4: | signal in the S direction on the track in the E corner |  | bit 5: | signal in the N direction on the track in the E corner |  | bit 6: | signal in the S direction on the track in the W corner |  | bit 7: | signal in the N direction on the track in the W corner | m2 bits 7..4: bit clear = signal shows red; same bits as in m3OpenTTD bits in m4:
          
           | bits 1..0: | type of signal: |  | 00: | normal signals |  | 01: | pre-signals |  | 10: | exit-signals |  | 11: | combo-signals |  | bit 2: | set = semaphore signals, clear = light signals | m1: owner of the trackm2 bits 0..3:
        
         | 0 | on bare land |  | 1 | on grass, no fences |  | 2 | fence on the NW side |  | 3 | fence on the SE side |  | 4 | fences on the NW and SE sides |  | 5 | fence on the NE side |  | 6 | fence on the SW side |  | 7 | fences on the NE and SW sides |  | 8 | fence on the E side (track in the W corner) |  | 9 | fence on the W side (track in the E corner) |  | A | fence on the S side (track in the N corner) |  | B | fence on the N side (track in the S corner) |  | C | on snow or desert | m3 bits 0..3 = track type:
        
         | 0 | conventional railway |  | 1 | electrified railway |  | 2 | monorail |  | 3 | maglev | m5 bits 7 and 6 set: railway depot / checkpoints
      
       m5 value C0..C3: railway depot
        
         | m5 bits 1..0 |  | direction: exit towards: |  | 00 | NE |  | 01 | SE |  | 02 | SW |  | 03 | NW | m5 value C4..C5: checkpoint
        
         | bit 0 |  | clear | in X direction |  | set | in Y direction | m1: owner of the depot / checkpointm2: For waypoints, index into the array of waypoints.m3 bits 0..3 = track typem4 bits 0..3 = ground type, as per m2 bits 0..3 for railway tiles. | 
  
   | 2 | 
    m5 bits 7..4 clear: road
     
      m5 bits 3..0: road layout: bit set = road piece present:
       
        | bit 0: | NW piece |  | bit 1: | SW piece |  | bit 2: | SE piece |  | bit 3: | NE piece | m1: owner of the roadm2: Index into the array of towns, 0 for non-town roadsm4 bits 0..3: counter for the roadworksm4 bits 4..6:
       
        | 0 | on bare land |  | 1 | on grass |  | 2 | paved |  | 3 | with streetlights |  | 5 | tree-lined |  | 6 | on grass with road works |  | 7 | paved with road works | m4 bit 7 set = on snow or desertm5 bit 4 set, bits 7..5 clear: level crossing
     
      m5 bit 3: clear - road in the X direction, set - road in the Y direction (railway track always perpendicular)m5 bit 2: set if crossing lights are onm1: owner of the railway trackm2: Index into the array of towns, 0 for non-town roadsm3 bits 0..7: owner of the roadm4 bits 3..0: track typem4 bits 4..6: 0 - on bare land, 1 - on grass, 2 or higher - pavedm4 bit 7 set = on snow or desertm5 bit 5 set: road depot
      
       m5 bits 3..0 - direction: exit towards: 0 = NE, 1 = SE, 2 = SW, 3 = NWm1: owner of the depotm4 bit 7 set = on snow or desert (not displayed, but set internally) | 
  
   | 3 | Town building 
     m2: Index into the array of townsm4: town building type:Note: In the climate list, 'sub-arctic' means below the snow line, and 'snow' means above the snow line in the sub-arctic climate.
 
       | Type | Size | Climates | Description | 
|---|
 | 00 | 1×1 | temperate | tall office block |  | 01 | 1×1 | temperate | office block |  | 02 | 1×1 | temperate | small block of flats |  | 03 | 1×1 | temperate | church |  | 04 | 1×1 | temperate, sub-arctic, sub-tropical | large office block |  | 05 | 1×1 | snow | large office block |  | 06 | 1×1 | temperate | town houses |  | 07..08 | 1×2 | temperate | hotel |  | 09 | 1×1 | temperate, sub-arctic, sub-tropical | statue |  | 0A | 1×1 | temperate, sub-arctic, sub-tropical | fountain |  | 0B | 1×1 | temperate | park (with a pond) |  | 0C | 1×1 | temperate | park (with an alley) |  | 0D | 1×1 | temperate | office block |  | 0E..10 | 1×1 | temperate | various types of shops and offices |  | 11 | 1×1 | temperate, sub-arctic, sub-tropical | modern office building |  | 12 | 1×1 | temperate | warehouse |  | 13 | 1×1 | temperate | office block (with spiral stairway on the side) |  | 14..17 | 2×2 | temperate | stadium |  | 18 | 1×1 | temperate | old houses |  | 19 | 1×1 | temperate | cottages |  | 1A | 1×1 | temperate | houses |  | 1B | 1×1 | temperate | flats |  | 1C | 1×1 | temperate | tall office block |  | 1D | 1×1 | temperate | shops and offices |  | 1E | 1×1 | temperate, sub-tropical | shops and offices |  | 1F | 1×1 | temperate | theatre |  | 20..23 | 2×2 | temperate, sub-arctic, sub-tropical | stadium (modern style) |  | 24 | 1×1 | temperate, sub-arctic, sub-tropical | offices (the modern 'vertical tube' style) |  | 25 | 1×1 | sub-arctic | houses |  | 26 | 1×1 | snow | houses |  | 27 | 1×1 | temperate | cinema |  | 28..2B | 2×2 | temperate | shopping mall |  | 2C | 1×1 | sub-arctic | flats |  | 2D | 1×1 | snow | flats |  | 2E | 1×1 | sub-arctic | houses |  | 2F | 1×1 | snow | houses |  | 30 | 1×1 | sub-arctic | houses |  | 31 | 1×1 | snow | houses |  | 32 | 1×1 | sub-arctic, sub-tropical | tall office block |  | 33 | 1×1 | snow | tall office block |  | 34 | 1×1 | sub-arctic | tall office block |  | 35 | 1×1 | snow | tall office block |  | 36 | 1×1 | sub-arctic, sub-tropical | tall office block |  | 37 | 1×1 | snow | tall office block |  | 38 | 1×1 | sub-arctic | houses |  | 39 | 1×1 | snow | houses |  | 3A | 1×1 | sub-arctic | shops and offices |  | 3B | 1×1 | snow | shops and offices |  | 3C | 1×1 | sub-arctic | church |  | 3D | 1×1 | snow | church |  | 3E | 1×1 | sub-arctic | houses |  | 3F | 1×1 | snow | houses |  | 40 | 1×1 | sub-arctic | shops and offices |  | 41 | 1×1 | snow | shops and offices |  | 42..43 | 1×2 | sub-arctic | hotel |  | 44..45 | 1×2 | snow | hotel |  | 46 | 1×1 | sub-arctic, sub-tropical | shops and offices |  | 47 | 1×1 | snow | shops and offices |  | 48 | 1×1 | sub-arctic | tall office block |  | 49 | 1×1 | snow | tall office block |  | 4A..4B | 2×1 | sub-arctic | tall office block |  | 4C..4D | 2×1 | snow | tall office block |  | 4E | 1×1 | sub-tropical | houses (with a tree in a corner) |  | 4F, 50 | 1×1 | sub-tropical | houses |  | 51 | 1×1 | sub-tropical | houses (suburb-type) |  | 52 | 1×1 | sub-tropical | flats |  | 53 | 1×1 | sub-tropical | church |  | 54 | 1×1 | sub-tropical | houses (with two trees in front) |  | 55, 56 | 1×1 | sub-tropical | flats |  | 57..58 | 2×1 | sub-tropical | tall office block |  | 59 | 1×1 | sub-tropical | flats |  | 5A | 1×1 | sub-tropical | tall office block |  | 5B | 1×1 | toyland | church |  | 5C..61 | 1×1 | toyland | various types of toyland houses |  | 62 | 1×1 | toyland | tall office block |  | 63..64 | 1×2 | toyland | houses ('shoe' style) |  | 65 | 1×1 | toyland | tall office block |  | 66 | 1×1 | toyland | igloo |  | 67 | 1×1 | toyland | tepees |  | 68, 69 | 1×1 | toyland | shops and offices |  | 6A | 1×1 | toyland | tall office block |  | 6B | 1×1 | toyland | statue |  | 6C | 1×1 | toyland | teapot-house |  | 6D | 1×1 | toyland | piggy-bank | m3 bits 7..6: stage of construction (3 = completed)m5 bits 2..0: construction counter, for buildings under construction incremented on every periodic tile processingOn wraparound the stage of construction in m3 is increased
for large office blocks (types 04 and 05):
      
       m1 bits 6..0: position of the liftm1 bit 7: if set the lift is movingm5 bit 7: if set then m5 bits 5..0 hold the destination floor of the lift, which could be 0..6, except 1.So the building has 6 effective floors. This is due to the fact that the first floor is 2 'normal' floors high.
 One 'normal' floor has a height of 6 lift positions.
 | 
  
   | 4 | Trees 
     m5 bits 7..6: number of trees minus onem5 bits 2..0: growth status: 0..2 - one of trees is growing, 3 - all trees are fully grown, 4..6 - one of trees is witheringm3 bits 7..0: type of trees:
      
       Note: the actually displayed set of trees depends on both type and number of trees| 00..0B | temperate climate trees |  | 0C..13 | sub-arctic climate trees |  | 14..1A | rainforest trees |  | 1B | cactus plants |  | 1C..1F | sub-tropical climate, non-rainforest, non-desert trees |  | 20..28 | toyland trees | m4 bits 7..5: type of hedge on the SW border of the tile (1 through 6, or 0=none)m4 bits 4..2: type of hedge on the SE border of the tile (1 through 6, or 0=none)m2 bits 5..4:
      
       | 0 | on grass |  | 1 | on rough land |  | 2 | on snow or desert; m2 bits 7..6 - amount of snow or desert (for desert always set to 3 in TTD) | m2 bits 3..0: update counter, incremented on every periodic processing.on wraparound the growth status is updated (or, if it's 3, a random action is taken)
m1: owner (normally 10) | 
 
  | 5 | Station tile 
    m5: tile type:
     
      
       | 00..07 | railway station 
         | 00..01 | open platform |  | 02..03 | open platform with station building |  | 04....07 | roofed platform |  | bit 0: clear = in X direction, set = in Y direction |  |  | 08..33 | large airport 
        | 0B | pad 1 |  | 16..19 | runway middle |  | 1A | runway ending |  | 1C | control tower |  | 20 | hangar |  | 21 | pad 3 |  | 22 | pad 2 |  | 27..32 | radar (animated) |  | 33 | transmitter |  | The initial layout of a large airport is (rows in Y direction, columns in X direction): 
1F 1B 1E 33 26 1A
09 24 0B 0C 0D 16
21 1D 23 0E 0F 17
09 22 0D 11 10 18
09 08 14 13 12 19
20 0A 15 1C 27 1A
 |  |  | 34..41 | small airport 
        | 3A..3D | field with the wind meter (animated) |  | 3E | runway south ending |  | 3F | runway middle |  | 40 | runway north ending |  | 41 | hangar |  | The initial layout of a small airport is (rows in Y direction, columns in X direction): 
36 3A 40
35 39 3F
34 38 3F
41 37 3E
 |  |  | 42 | heliport |  | 43..46 | lorry loading area : exit towards: |  | 47..4A | bus station : exit towards: |  | 4B | oilfield |  | 4C..51 | ship dock 
        | 4C | SW coast part |  | 4D | NW coast part |  | 4E | NE coast part |  | 4F | SE coast part |  | 50 | X direction water part |  | 51 | Y direction water part |  |  | 52 | buoy |  | 53..A7 | used by RichK's larger airports | m1: owner of the stationm2: index into the array of stationsm3 bits 0..3: track type for railway stations, must be 0 for all the other stationsm3 bits 4..7: persistent random data for newstationsm4: custom station id; 0 means standard graphics | 
  
   | 6 | 
     m5: tile type:
      
       | 00 | water |  | 01 | coast or riverbank |  | 10..1B | canal locks 
         | 10 | middle part, (SW-NE direction) |  | 11 | middle part, (NW-SE direction) |  | 12 | middle part, (NE-SW direction) |  | 13 | middle part, (SE-NW direction) |  | 14 | lower part, (SW-NE direction) |  | 15 | lower part, (NW-SE direction) |  | 16 | lower part, (NE-SW direction) |  | 17 | lower part, (SE-NW direction) |  | 18 | upper part, (SW-NE direction) |  | 19 | upper part, (NW-SE direction) |  | 1A | upper part, (NE-SW direction) |  | 1B | upper part, (SE-NW direction) |  |  | 80..83 | ship depots 
         | 80 | ship depot, NE part (X direction) |  | 81 | ship depot, SW part (X direction) |  | 82 | ship depot, NW part (Y direction) |  | 83 | ship depot, SE part (Y direction) |  | m1: owner (for water and coasts normally 11) | 
  
   | 7 | Void Tiles of this class form an invisible, one tile wide border at the south (bottom) edges of the map,so as to protect several algorithms from the consequences of a wraparound at the edges.
 | 
  
   | 8 | Industry tile 
     m5: type:(note: this is not the same as the industry type, which is stored in the array of industries)
 
       | 00..06 | coal mine 
         | 00 | wheel tower when not animated |  | 01 | wheel tower when animated animation state in m3 bits 5..0; m3 bit 6 set = sound already generated
 |  |  | 07..0A | power station 
         | 08 | chimney |  | 0A | transformer; animation progress in m3(valid range 0..7) |  |  | 0B..0F | sawmill |  | 10..11 | forest |  | 12..17 | oil refinery |  | 18..1C | oil rig |  | 1D..20 | oil wells 
         | 1D | not animated |  | 1E..20 | various stages of animation; progress of animation in m3 |  |  | 21..26 | farm |  | 27..2A | factory (temperate climate) |  | 2B..2E | printing works |  | 2F..33 | copper ore mine 
         | 2F | wheel tower when not animated |  | 30 | wheel tower when animated; animation state in m3 bits 5..0; m3 bit 6 set = sound already generated |  | 31 | chimney |  |  | 34..39 | steel mill |  | 3A..3B | bank (temperate climate) |  | 3C..3F | food processing plant |  | 40..47 | paper mill |  | 48..58 | gold mine 
         | 4F | wheel tower when not animated |  | 58 | wheel tower when animated; animation state in m3 bits 5..0; m3 bit 6 set = sound already generated |  |  | 59..5A | bank (sub-arctic or sub-tropical climate) |  | 5B..63 | diamond mine |  | 64..73 | iron ore mine |  | 74 | fruit plantation |  | 75 | rubber plantation |  | 76..77 | water supply |  | 78 | water tower |  | 79..7C | factory (sub-tropical climate) |  | 7D..80 | lumber mill |  | 81..82 | candyfloss forest 
         | 82 | candyfloss 'trees' cut down |  |  | 83..86 | sweet factory |  | 87..88 | battery farm |  | 89 | cola wells |  | 8A..8D | toy shop |  | 8E..93 | toy factory 
         | 8F | Animated part; animation state in m3 (valid range 00..31) Tile animation is started (m4 zeroed) on the periodic processing.
 While the animation is in progress, m4 holds the number
                        of animation cycles that have already taken place.
 when this number reaches 8 the animation is stopped.
 |  |  | 94..9B | plastic fountains (various stages of cyclic animation) |  | 9C..9F | fizzy drink factory |  | A0..A3 | bubble generator 
         | A1 | generators |  | A2 | bubble capture facility; animation state in m3 (valid range 00..27) |  |  | A4..A6 | toffee quarry 
         | A5 | animated part; animation state in m3 (valid range 00..45) |  |  | A7..AE | sugar mine 
         | AE | animated part; animation state in m3 (valid range 00..5F) |  |  |  | m2: index into the array of industriesm1 bit 7: clear = under construction
      
       m1 bits 4..2: construction counter, for buildings under construction incremented on every periodic tile processingm1 bits 1..0: stage of construction (3 = completed), incremented when the construction counter wraps aroundthe meaning is different for some animated tiles which are never under construction (types 01, 1E..20, 30, 58; see above)
 | 
  
   | 9 | 
     m5 bits 7..4 clear: tunnel entrance/exit
      
       m5 bits 3..2: 0 - railway tunnel, 1 - road tunnelm5 bits 1..0 - direction: entrance towards: 0 = NE, 1 = SE, 2 = SW, 3 = NWm1: owner of the tunnelm3 bits 3..0 = track type for railway tunnel, must be 0 for road tunnelm4 bit 7 set = on snow or desertm5 bit 7 set: bridge ramp
      
       m1: owner of the bridgem3 bits 3..0 = type of track on the bridge, must be 0 for road bridgem5 bits 3..2: 0 - railway bridge, 1 - road bridgem5 bit 0..1: DiagDirection onto the bridgem2 bits 7..4: bridge type:
        
         | Type | Max. speed (mph) | Description | 
|---|
 | 0 | 20 | wooden |  | 1 | 30 | concrete |  | 2 | 40 | girder, steel |  | 3 | 50 | suspension, concrete |  | 4 | 60 | suspension, steel |  | 5 | 70 | suspension, steel |  | 6 | 100 | cantilever, steel |  | 7 | 130 | cantilever, steel |  | 8 | 150 | cantilever, steel |  | 9 | 160 | girder, steel |  | A | 200 | tubular, steel | m4 bit 7 set = on snow or desert
     | 
  
   | A | 
     m5: tile type:
      
       | 00 | transmitter |  | 01 | lighthouse |  | 02 | company statue |  | 03 | company-owned land |  | 80..93 | company headquarters (5 sets of 4 tiles each, updated quarterly depending on the company performance) | m1: owner of the object (for lighthouses and transmitters normally 10) | 
  | Classes B through F are reserved. The presence of a tile in one of the reserved classes will crash OTTD. |