In the previous video we had a look at how to create flicker free block occupancy with momentary sensors. We used an intermediate switch as a memory for the sensor signal. Once triggered, it stays on, does not flicker. In turn it triggers a Flagman inside the block, which now represents the block occupied status.
We can decide when we want to turn the memory switch off again. I used the stop marker for that. This gives me two advantages:
- I can see if a train is driving in the block (status occupied = on) or stands still at the stop marker (status occupied = off).
- The block can be released as soon as the train enters the next block, which allows a new train in at quite an early stage (the tail of the train is still in the block when the new train already starts to drive).
I like this early release of blocks, it gives a bit higher throughput of traffic. This depends of course on personal preferences. Let’s have a look at the different Schedule Rules for release of blocks.
We go to the Schedule Properties window, click the Rules tab and scroll down until we find the chapter called ‘Release of Blocks and Routes’.
If we have not yet changed anything, by default this will be ‘At Stop Marker’, which means that the previous block and route are released only when the train has reached the stop marker of the next block. While that is a very safe method (provided your trains are shorter than the blocks), it also is a very slow method. A new train is only allowed into the previous block, when the old train has reached the very end of the next block. This results in low throughput.
A bit more throughput can be gained when the setting is changed into ‘Upon Complete Entry’. This means as much as that TC calculates when the train is completely inside the new block. It does this based on the specified train length and on the calibrated speed profiles, which are both mandatory for this method to work well.
While we can now see a new train start to drive into the previous block a bit sooner … it was still a bit slow to my liking. I went a step further and put the setting on ‘Smart or upon Entry’.
Smart means that the previous block is already released when the train reaches the next block AND when it is NOT occupied. Here comes reason nr 2 above in play: the block is not occupied anymore, since I already turned the occupied status off at the stop marker. So, when the train reaches the next block … the previous block is immediately released, even while the train’s tail may still be in. But that never poses a problem … since it is driving and will drive on to at least the next stop marker … no collision is ever going to happen and throughput is nicely enhanced! Not really prototypical, but more trains drive around this way, in stead of stand still. 🙂
The video shows the difference between the two methods, with live footage of trains on the move.