If you were inclined to clone and edit all the textures to make them grayscale, then that would be a way to do it. Using batch process in Photoshop would make it fairly swift procedure so long as you could isolate all the textures into one folder for processing.
However, a word of caution here, when turning textures to a single channel grayscale image in Photoshop, do not make the mistake most people do, which is to simply go to the Image menu and choose Grayscale; doing that will give you no control over the contrast of the grayscale you end up with. Any version of Photoshop after CS2 will let you use the Adjustments menu to choose a Black and White conversion, which gives you more control. At that point it is still a three channel RGB image, so you will still have to choose Grayscale mode if you actually do want a single channel grayscale, although Trainz won't care about that, but doing it that way will mean you have more control and will mean a smaller texture file too. This is why using a batch action process would be a good idea, because otherwise it would be tedious to do that with lots of textures one at a time. If you have a version of Photoshop prior to CS2, there is no Black and White adjustment palette, but you can still do something vaguely similar be using the Channel Mixer and ticking the 'Monochrome' option on that palette down in the bottom left corner of that palette, again you would then also have to select Grayscale mode to make it a single channel image if you were looking to save on disk space, but again, you could create an action to make that speedier.
Al
