That's the reason bad things happen. Before the added capacity, drivers' actions are restricted by problem statement, so signaling isn't needed, its role is filled. If all drivers decide to ignore the addition, and effectively signal to each other that they actually will, they end up with the old plan, better than otherwise, and so would choose to precommit to that restriction. More freedom made signaling the same plan more difficult, by reducing information. But of course, with new capacity they could in principle find an even better plan, if only they could precommit to it (coordinate their actions).