Transport Tycoon Forums

I have a line that is bidirectional and has two lanes per direction. It is signalled with bidirectional signals, so a train can choose to pass slow or broken down trains--trains shouldn't get stuck.

However, occaisonally two trains break down and the train that is stuck behind them reverses. Or, a train will enter the main line from the wrong shunt, and start going in the wrong direction. Since all the signals on the main line are bidirectional, the train can go the wrong way for a LONG time before I notice.

Is there a way to properly signalize this line so that it is breakdown-proof but also one way? Here's a picture and saved game with an example of what one part of my track looks like. (I'm only interested in the circled part, I realize that in the example it's definitely one way--pretend that something might enter from the wrong side.)

but there are no presignals in there! i mean, those with the tiny whiteor yellow bar under the light. using them may solve you the problem, using two way for entrances and one way combo presignals in the middle of each track, thus disabling trains going backwards.

You will also run into problems if you have a really long train.

Raven: I had tried with pre-signals, but I was using exit signals (with the grey bar) for the one-ways, not combo signals. With the exit signals, I kept being left with stray red signals after a train had passed the whole area, but with combo signals it works! Thanks! Can you explain to me why? I've read the ttdpatch manual's section on pre-signals to try to understand how they work in TTD/OpenTTD, but obviously there's something I'm not getting.

lucaspiller: I don't see how that can happen. No matter how long a train is, there will be crossovers to get around it. I have 20-car trains on a network like this, and I haven't seen problems regarding length. Could you show me how it could cause problems?

Well it wouldn't really cause terrible problems but some of the cross over bits would be useless because a train is blocking the entrance.

Presignals:
On the entrance section you will need an signle entrance signal, with a horizontal yellow bar. For each exit you will need a double exit signal, with a vertical gray bar.

Have a look at this picture,

and this page of the TTDPatch Manual.
http://wiki.ttdpatch.net/tiki-index.php ... ignalsWork

Thanks so much for your help guys, but I've discovered that neither solution is perfect. I've attached a couple of pictures to clarify.

Following lucaspiller's solution, I get the first picture. If the train at the red arrow broke down, trains would still go through the green signal at the blue arrow--even though they'd only have to stop again behind the broken down train. I'd like the signal at the blue arrow to be red in this situation, so trains go around broken down trains.

With Raven's solution, I get the second picture. Imagine train A is broken down, and train B is passing it. Although both tracks are now occupied, the signals at the white arrows are green. So train C comes along, goes through the one-way signal, and makes a choice at the two-way signals--the wrong choice. Now it has to wait for train A to recover, instead of following train B. I'd like the signals at the white arrows to be red when both tracks are occupied, so train C would stop at the one-way signal and take whichever track becomes free first.

The last pic shows what I'd like: If there's any train anywhere in A, no other train should enter it. Ditto for B. If BOTH are blocked, trains should stop at the red dot.

I hope there's a way to accomplish this! I've been playing with signals for quite a while trying to find the right combination, but nothing seems to work

Ah, thats easy, you need to allow the middle pre signal block things.

The signal before the current entrance signal needs to be an entrance signal and the current entrance signal needs to be a 'combo' signal, with a vertical yellow bar.

Also you have set up the presignals wrong.

Entrance signals have a horizontal yellow bar.
Combo signals have a vertical yellow bar.
Exit signals havea vertical gray bar.

Sorry, I had the pictures in the wrong order. Fixed now.

lucaspiller, could you please show me how you think it should look? I'm having trouble understanding from your last description, and I know which pre-signal is which.

Thanks,
vasi

Ok, I think it needs more of an explanation so here I go:

Entrance signals mark the start of the section. If no combo or exit signals are green this will also be red.

Exit signals mark the end of a section, these behave just like ordinary signals but control entrance signals.

Combo signals are something that goes between entrance signals and exit signals, and behave like a bit of both. They act like an entrance signal only being green when an exit signal is green but act like an exit signal controlling an entrance signal.

See the picture, it shows what you need to do to sort it all out.