Version 1.8 is now the default game version! After a smooth beta period 1.8 is now ready for the wider playerbase. Its main focus touches the very core of the game: train AI. In 1.8 the track pathfinder powering train AI has been improved with new capabilities, and large parts of said AI have been rewritten to take advantage of it. But as usual other smaller features are also implemented in this new major version.

Track + point pathfind

The track and train pathfinder now supports precise starting points and goals, rather than whole pairs of tracks as in previous versions. This in turn means line timing now matches the intuitive real world concepts of arrival, departure and leg, and keeping track of things like braking time or "reach middle of platform" are not needed anymore. This new capability also powers a new, much improved braking system.

Push-pull

One of the consequences of track + point pathfinding is trains being able to "flip in place" when they need to reverse direction, rather than going all the way to a track dead end to do so. Additionally, when flipping, trains are now capable of doing so in a push-pull way: if the train composition is enabled for push pull (with the push-pull flag, or by having a head and tail car tagged as control or locomotive), its cars won't change orientation on direction changes.

Improved braking

Previous versions didn't really implement braking. Instead a check was done in the train AI if the train had crossed into the center of the pair of tracks designated as a goal, and a speed limitation as forced just at the point, with no regard for realism.

But in 1.8 trains approaching a line stop now start braking at the correct braking distance given their current speed, independently of how many track segments are required to cross over to arrive to the destination. And not just for stops: every static (so, not signals or other train rear ends) speed change in the train path is equally anticipated and braked for in advance. Trains won't start accelerating again until the entire length of the train is past the slower track segment.



The braking acceleration can now be controlled by mods. The default braking rate (1 m/s/s) is a bit fast compared to most non-subway trains in the real world, but I think it's better to keep it a bit fast so it's closer to old behaviors. Modders can of course change it for their mods. Players can also set a maximum braking and acceleration value at the line level.

Unified append and branch track tool

Branching (and, new in 1.8, merging) tracks is now a mode of the track append tool. The track append tool will now seamlessly support both appending tracks and creating new branches, if clicking on top of existing tracks. And when "holding" a track while appending to it, it will also propose to merge it as a branch if hovering on top of existing tracks. This behavior can be toggled with the old keybind and/or branch button in the UI.

Shared games browser

The shared games feature has proven popular, with more than 400 shared games! In 1.8 you can also browse these games in a listing, with sorting criteria for various parameters:

Red signal info in train window

When trains are stuck at a red signal, it's sometimes hard to understand why. In 1.8 when you open the train window and the train is waiting at a red signal, the train path beyond the signal will be displayed, stopping at the point where it found an obstacle, and a text label will be displayed at that point identifying the train or track reservation that failed the signal check.

Full details

The devblog posts for March and April contain detailed explanations for these and other changes in 1.8:

https://carloscarrasco.com/nimby-rails-march-2023/

https://carloscarrasco.com/nimby-rails-april-2023/