Hussar
Legend
I have a hard time imagining how a 'site-based' adventure could be a railroad.
Rather easily unfortunately. If the DM decides that the orcs in the cave ARE going to capture your characters, then it's a railroad. If the DM decides that you ARE going to free the prisoner and you ARE going to trust him, then its a railroad. If the DM decides that, no matter what you do, you MUST go to room X and no amount of lateral thinking will cause the baddies to leave their room then buckle up.
((Incidentally, ALL of the above happened to me in the Caves of Chaos.))
OTOH, sometimes the DM has the reins and it is perfectly realistic. Take my current campaign. The party has taken shelter in a Celestial garrison. The party, being good and being pretty tough, is offered membership in the garrison. Not forced, mind you, simply offered. The party accepts and is co-opted into the military forces of the garrison.
Now, as the DM, I control the leader of that garrison. If I hand orders to the party, is that railroading? If I tell the party to go out and scout yonder hill and report back what they find, am I railroading? The party has two choices, leave or accept. If they want help from the garrison, they have to be members of it. The garrison has long been under siege and doesn't have the resources to sell to random adventurers who are not going to help them. They don't need cash, they need warm bodies.
So? Am I guilty?