Priorities
From #OpenTTDCoop
Contents |
Making Priorities
You can make priorities using presignals.
Part 1: The basic priority
Important: Signal B has to be a double signal.
If Exit Signal B is red then Entry Signal A is also red, so what do we have? A track priority!
Part 2: Add a Combo presignal
If Exit Signal C is red then Combo Signal B is red, making Entry Signal A red. So we have a bigger priority than in Part 1.
Part 3: Why more Combos aren't good
It is not a good idea to increase the Combo Presignals: in this picture the second train stops at Combo Signal A. It can't wait at Combo Signal B, because the first train is in B's block. This slows down the line that supposedly has priority! Trains that aren't on the priority line will have a tough time getting through, as well. Notice: We don't have this problem in Part 2, since Presignal C is an Exit Signal, not a Combo one.
Part 4: A way to make "unlimited" priority
But there is a trick to increase the priority without slowing down the line that has priority:
This Priority junction doesn't have Part 3's problem, since signals I-F are regular signals, and allow the train to pass through. They can't access the tracks the Combo Signals are on. Combo-signal E will turn red as soon as the train enters the signal-block defined by E, I, and the regular signal behind the train. Because Combo E is red, D must turn red, and so on until B, which functions as the exit-signal for A, the entry-signal. When thinking priorizers, think backwards in the direction the signals are facing, and not necessarily forward in the direction the trains are going.
Part 5: Make the priority length depend on the train length
In games with different train length situations may occur where the gap between two trains on the ML is sufficiently large to fit in a short train but not a long train.
Making the priority of the ML long enough that the SL is always blocked as if a long train waits would waste capacity of the network. The solution is to shorten the priority for a short train entering from the side line. The solution is to extend the prio in part 4 such that a connection is made to the SL. The connection has to be such that the long train waiting in front of A triggers this part (combo signal between B and C becomes red) while the short train does not trigger that signal when waiting in front of A.
