How to think about the clause in this sentence: We're looking at the benefits of systems which control their speed as a way of preventing that. 是什麼意思

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The original article:
For example, most of us would expect older drivers always go slower than everyone else but surprisingly, we found that in 30mph zones they struggled to keep at a constant speed and so were more likely to break the speed limit and be at risk of getting fined. We're looking at the benefits of systems which control their speed as a way of preventing that.

I wonder which one is right:
We're looking at the benefits of systems (which control their speed) as a way of preventing that.
We're looking at the benefits of systems (which control their speed as a way of preventing that).

i.e.
Which is the clause of the sentence, "which control their speed" or "which control their speed as a way of preventing that"?

Thank you!