Train Research Unlock

Train Research shouldn't be available until after Vehicle Part II has been unlocked. There is no point in being to build a rail line if you can't build the trains because you haven't unlocked GLASS yet.
Or make coal trains available with Vehicle Parts I and Diesel trains available after Vehicle Parts II is unlocked.

I disagree. Having the ability to construct the rails before glass allows you to preplan your rail network as you are waiting for the research to finish.