http://svn.openttd.org/trunk/known-bugs.txt schrieb:Forbid 90 degree turns does not work for crossing PBS paths[FS#2737]:
When you run a train through itself on a X junction with PBS turned on
the train will not obey the 'forbid 90 degree turns' setting. This is
due to the fact that we can not be sure that the setting was turned
off when the track was reserved, which means that we assume it was
turned on and that the setting does not hold at the time. We made it
this way to allow one to change the setting in-game, but it breaks
slightly when you are running your train through itself. Running a
train through means that your network is broken and is thus a user
error which OpenTTD tries to graciously handle.
Fixing this bug means that we need to record whether this particular
setting was turned on or off at the time the reservation was made. This
means adding quite a bit of data to the savegame for solving an issue
that is basically an user error. We think it is not worth the effort.