PrepTest 124

Incorrect. While some wouldn't, the stimulus notes that many would, and thus the average speed limit would increase.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
If highway speed limits are increased:
(1) Most current speeders would follow the higher speed limits
(2) Almost everyone who currently drives the speed limit would drive faster
resulting in higher average speeds on highways, thus decreasing highway safety.

Answer Anticipation:
This argument seems complex at first glance, but there's quite a bit we can ignore!

First, we can ignore that opposing point—the Editorialist quickly moves away from what some people argue" and doesn't refer back to that argument other than to bring in that highway speed limits are increasing, so it's not relevant to the logic.

Second, we can ignore everything about the results of the speed limit increase! Why, you ask? Well, those results lead to the intermediate conclusion that the average highway speed will increase if speed limits are raised. Based on the facts presented, that's valid—if speeders are following the new limits (which are set at their average speed) and non—speeders are going faster, then the average will increase, and so there's no gap in the reasoning there. Ergo, we can't weaken that part of the argument—there needs to be a logical flaw in the argument for us to be able to weaken it.

So we're left with the following as the argument we need to weaken:
Increasing the highway speed limit will increase average highway speeds, so increasing the highway speed limit will decrease highway safety.

Is there any premise offered to justify that faster speeds will guarantee less safety? There is not. That's the flaw in the argument that we can attack in order to weaken it. Let's look for an answer that establishes some reason to think that a higher speed might not (at least in this case) lead to less safety.

Answer Explanation:
This answer choice discusses average speeds on highways and safety, so we should strongly consider it. It states that uniformity of speed—which the stimulus does suggest is increasing as speeders now drive the higher speed limit and non—speeders drive that, as well—is more important to safety than having a lower average speed. That means that the proposal to increase speed limits—which would, again, increase both uniformity and speed—might make the highways safer, thus weakening the argument. This is our answer.

Key Takeaway:
The LSAT has many questions that include a lot of extra "junk"—information meant solely to distract. If you start with the conclusion and work backwards to what's supporting it, you can usually figure out what's relevant and what isn't, which is going to make your job of anticipating an answer and then finding the right one much easier.

Incorrect. The conclusion is about a change to highway safety. That could be a shift from a 2% accident rate to a 6% accident rate (or vice versa). In other words, even if most speeders aren't in accidents, a significant number could have been that drove up the danger on the highway.

Incorrect. Even so, the stimulus notes that most would obey the new speed limits, so this answer is already considered in the argument.

Incorrect. There's no way to know how they make this determination, and what they would believe is safe under the new speed limits, so we can't analyze the impact this answer has on the argument—and it is thus incorrect.