As a apparent "writer" I sometimes find it hard to stop the darn railroad! Looking back at AD&D Dragonlance modules, there are very specific goals in mind, and in some cases there are "what to do/trouble shooting" sections within modules to make sure you continue on ye old railroad.
Looking further back at older modules like Keep On The Borderlands, I realize that the entire module was left completely, or atleast fairly open ended. It takes until the end of the module to realize that there is a evil cult that is not only controlling things in the cave, but also in the keep as well. Obviously some players may never realize this, some players might even team up with the cult and help with any degenerate behavior that they have planned.
From a GMing stand point, I grew up with and wrote adventures for AFF (advanced fighting fantasy), which was all based around a slight railroad and "scenes" within each module, the gist of which was you ended up rooting for the PC's to finish the adventure, and the campaign grew from there (pathfinder anyone?).
I am starting to believe that in order to write really good material for the OSR and GM's you need to give plenty of options, and possibilities and basically let the dice fall where they may, to coin a phrase. The problem is the conundrum of "this is how I see it and how it would be fairly epic, ie RAILROAD" vs "well here is a bunch of dungeons stocked with monsters, I won't give you any more details on why they are there and what they are doing".
Within the writing I am currently doing on the enormity project, I have created factions , various hints along the way, and I have started to consider, although it may not happen a section entitled "well its not necessarily a railroad, but here's the plot just in case".
I do believe however that tying the GM and or players hands is a bad idea, so I am trying to figure out the best way to walk the line of "here is what is going on" and "here's your free will, do with it what you may".