A Block is a simple stretch of track that connects other track objects like switches, control points etc. Blocks are also used to divide a longer stretch of track into smaller sections – the blocks -, each of which will normally have only one train. With signals at the end of each block it is possible to safely run more than one train at a given time on a lengthy stretch of track by keeping them apart just by signals that control whether the next block ahead can be entered or not.
Logically, a CTC block is a line connecting two points – forming the left and right boundaries – and the distance between them determines the length of the block. Trains are running from left to right or vice versa.
On the scene diagram, a block is represented by a collection of simple track elements (other than switches, crossings, drawbridge tracks). These elements typically form a continuous polygon line, but it can be broken up into several lines indicating a track passing under another piece of track, or a track that continues from the right edge of the diagram to the left when the whole scene is broken up into chunks arranged from top to bottom – these pieces still belong to one block, and a click of any of these track elements will address the whole block (TB note: the break up is not possible there – all simple track element are lumped together if visually possible, and a break up creates two blocks which need to be linked together. Simple track elements cannot be moved to another block there).
Note, we use the term “(simple) track element” for the elements inside the block, each of them occupying a grid element on the scene, and the term “track object” for any logical unit trains can encounter. A block is therefore a track object containing several track elements shown on the grid.
A block is connected at both ends to other track objects, which can be another block, any type of switch, crossing, a drawbridge, a control point holding signals and triggers, or an entrance/exit (external or “extern”) point where trains enter or leave the territory. While externs and signals closely interact with the block nearby, they are not part of the block data.
A block can have a station, where trains may be required to stop. In some cases switching can occur using switches operated by the ground crew that are not shown on the diagram – and therefore not part of the territory data, which can result in a change of length or even the heading of the train.
There are speed limits are assigned to each block (except connector-only blocks). They are set up per traintype and can differ for each travel direction.
For details about block properties including things that can be manipulated on that level see here.
When the simulator is running the following colors are used to indicate the status of a block (note that some conditions don’t apply to every type of block):
- White – normal status, unoccupied, not part of a route
- Light Blue – unoccupied, not part of a route, but speed is reduced due to deteriorated track
- Green – part of a route (except for the start block), but not occupied (Arrows indicate direction of route)
- Red – block is occupied by one or more trains
- Blue – Blocked for maintenance work
- Magenta – Administratively blocked (e.g. for local switching)
Additionally, during Route Setting, if a start block is selected while the destination block is not, the following colors are used:
- Dark purple – Block is start block
- Yellow – Block can be reached directly and is free (train routes)
- Orange – Block can be reached directly but only if another train has moved away (train route) (1)
- Magenta – Block can be reached directly which may be occupied by another train (switch routes)
- Light Blue – Block can be reached directly but only if another train has moved away (switch route) (1)
(1) Routes with that destination can be stacked.
If no condition is met, blocks normally in white will be grayed, while others remain unchanged.
Note, if a particular block meets more than one condition, the color displayed indicates the first such condition in this list.
In Edit mode, the blocks are shown in white, with the following exceptions:
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During Route Test colors will be applied as if the simulator is in run mode (colors indicating some involvements of trains will not be used since there are no trains)
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If a block is selected in various functions, the block will be shown in yellow, while non-selected blocks will be grayed.
More details for some specific type of blocks can be found as follows: