Kamikaze Midget said:
I see!
The thing with 4e skill checks is that it appears to be directly relevant to the goal. Someone remembering that the alleyway is a dead-end halfway down the alleyway isn't going to gain anything from that knowledge that helps them escape the city. In 4e it might be more abstract. Presumably, you have secret passages out of the city, and, also presumably, a Streetwise check can allow a character to know about them. So assuming those are true, he can make it out of the city with a Streetwise check. Exactly which alleyway he uses is up to the DM, not up to the player, because the player doesn't actually know (but his character does). He doesn't run down that dead-end corridoor.
How would that differ from the way you do it?
I, as the DM, decided which alley has the way out, not which one the player runs down. Even the dice don't determine which alley the player runs down. Only the player makes that decision.
If the players were in the market place in a game I was running, and they needed to flee from the guards, I would give them a map of that they can see in the marketplace, show them where they are, and then show them where the guards are coming from.
If a player says, "I'm ducking down this alley and hiding," and points to the nearest alley, that is what he does and that is where he goes. I know there is no way out; I also know the next alley down does have a way out through a sewer grate.
The guards see the character head down that alley, but can't see him when they peer into the allet. The leaders says "You three stay here and guard this entrance. He has to be here somewhere, and I don't want him getting out." And goes off with the rest.
The player, still hidden, says, "Crap. I'm stuck. Is there anyway out of this alley?" I make him make a streetwise check and due to the success of it, reveal that, no there is no way out of this alley, but the next one down did have a sewer grate you probably could have squeezed through.
The player (and thus his character) did not think about what he should do before he did it, and headed down a dead end. When he finally did have a moment's pause to think, he realized his error. And error he could have prevented with an earlier streetwise check.
He had already ducked down the wrong allet, so saying that a streetwise check allows him to find a sewer grate there to escape through either (a) changes the reality of where the sewer grate is or (b) alters the reality of what the player said he did on his turn.
To me, that is the same as a wizard attacking a fire resistant creature with a fire spell, then making his knowledge check about the resistance, and saying either "you made your skill check so it doesn't have fire resist" (alrtering the reality of the creature) or (b) "oh that skill check means you actually used a cold spell. Roll damage." (altering the reality of what the player did on their turn).