Running Factorio v2.1.20.

After installing this mod and restarting Factorio without the SpaceAge mod being activated. I get the following error message:

Failed to load mods: Error in assignID: technology with name 'rail-support-foundations' does not exist.

At ROOT.technology.reinforced-rail-support.prerequisites[0]

Source: reinforced-rail-support (technology).

Mods to be disabled:
• various-rails (0.1.0)

Now, after a quick research it seems that 'rail-support-foundations' is only available when the SpaceAge mode is activated.
And looking at the data.lua file. I see that at line 408 that you have used the 'rail-support-foundations' as a prerequisite for the non-SpaceAge Elevated Rails version of the reinforced-rail-support recipe.

You might want to remove 'rail-support-foundations' and check the rest of the prerequisites for this recipe.

Ah, you actually revealed a second bug as well with this. Fixes out.

And a bonus fix that I did not see at first.

Thx, no error message when starting factorio or when loading a new or saved game. Will do so more testing through the weekend.