The TTDPatch Manual

Path Based Signalling

Enable path based signalling
2.0.1 alpha 41 or later


Configuration file: pathbasedsignalling on|off|bitsetting
Command line: -XI

Quick Info

This feature is somewhat dangerous, it may lead to train crashes if not used correctly (sometimes even if used correctly due to bugs in the code). Please read this entire page before trying to use it.

Pathbasedsignalling (PBS) allows multiple trains to share a junction, as long as their paths do not cross. As a train approaches a path-based junction, it will reserve a path through it (the rails it has reserved will show up darkened). If another train's desired path would cross the path of that train, it waits at the signal to reserve a path before entering the junction.

You will need the base graphics from the top of the second table on this page in order to have TTD properly display the PBS signals.

Detailed Info

Path based signalling is a feature that allows several trains in a signal block as long as their paths do not interfere. This greatly enhances the entrances and exits of stations as well as junctions.

This is a bit switch, with the following choices:

01autoconvertpresigConvert pre, exit and combo signals into PBS signals
12manualpbssigAllow manually setting PBS signals
24preservemanualpresig*Don't convert junctions with manually set signals into PBS
38showreservedpathShow reserved track pieces darker
416shownonjunctionpath*Show reserved track pieces on non-junction tiles too
532allowunsafejunction*Don't hold trains at an unsafe PBS signal
664allowunsafereverse*Don't stop trains that can't reverse safely

* Off by default (i.e. with just "pathbasedsignalling on")

The non-exclusive use of signal blocks is achieved by the trains "reserving" a path through the signal block. These reserved paths are then shown somewhat darker, and other trains will not reserve paths that interfere with them.


By default, all signal blocks which have at least one pre-signal, exit signal or combo signal leading into them will be converted to path-based signalling as soon as the block becomes clear for the first time. You can disable this by enabling the "autoconvertpresig" setting off the switch, in which case you have to set one signal in each block manually by cycling the states with Ctrl. If one signal is using path-based signalling, then all signals leading into that block will be converted to path-based signalling. This is the case even when automatic PBS blocks are disabled.

To make path-based signalling (PBS) work correctly, you have to obey a few rules in your junction design. Uwe Domaratius has written a very nice tutorial that explains how to use path-based signalling (among many other things).

Here are the requirements needed for making PBS work correctly:

Additional notes: