Several things in fact:
- We have proportional representation, which insures that the constitution of our parliament actually reflects the will of the voting populace (but that's true of most representative democracies as well, of course; I know that the UK with its FPtP system is a special case in that regard).
- There is no oppositional party system. No party has an absolute majority in parliament (as in the UK) and there are also no formal coalitions among parties (as, for example, in Germany). Individual bills are drafted and passed as a result of compromises among several parties.
- Same goes for the executive branch. Our government is a directorate of seven ministers elected from the country's four largest parties. We don't have a PM calling the shots and setting the agenda, but a committee of politicians with different ideas and ideologies being bound to constructively work together and compromise to actually get things done.
- All this means that bills passing through parliament are usually rather moderate compromises that already have the support of several parties. Swiss parliament procedures are usually very slow because of that whole "finding compromises" thing, but it also means less "scattershot politics". When a bill passes, it usually means that it's here to stay and won't be rescinded by a different government just a few years down the line.
- Furthermore, politicians are fully aware that controversial bills will ultimately have to pass a people's referendum. This means that they tend not to come up with proposals that go too far or are too radical, because radical (far-left or far-right) bills usually don't stand a chance in a referendum.
- With regards to people's initiatives, they're quite rare to actually pass, because you don't just have to carry the majority of the voting populace but of the Cantons (states) as well.
- Also, people's initiatives can only be proposed on a constitutional level. That means that if an initiative passes, it is up to the government and/or parliament to actually implement this and come up with the actual laws. Usually, this means that radical proposals put forward through people's initiatives are, if they actually manage to pass a vote, toned down significantly the parliamentary procedure that follows.
That's just a very rough outline of what I meant by "institutional safeguards". I'm not saying that it's perfect (nothing is), but considering the sheer amount of issues that we have the privilege to vote on each year, I think it's safe to say that the system works out very well in >90% of the cases. As I said, however, all of this is deeply ingrained in the structure and everyday reality of our political system, so it's a different beast to a purely representative democracy doing a one-off referendum on a momentous issue.
