LSAT Explanation PT 41, S3, Q26: Editorialist: Some people argue that highway

LSAT Question Stem

Which one of the following, if true, most seriously weakens the editorialist's argument? 

Logical Reasoning Question Type

This is a Weaken question. 

Correct Answer

The correct answer to this question is B. 

LSAT Question Complete Explanation

This argument is centered around the idea that increasing highway speed limits would lead to a decrease in highway safety. The editorialist provides the following premises: 1) most drivers who currently violate posted speed limits would obey higher ones, and 2) almost all drivers who obey current speed limits would likely increase their speed. The editorialist then concludes that higher average highway speeds would result, leading to a decrease in highway safety. The question type is Weaken, so we're looking for an answer choice that undermines the conclusion or the relationship between the premises and the conclusion.

Let's evaluate the answer choices:

a) Some drivers who obey current speed limits would not change their speeds after the introduction of the new speed limits.

- This answer choice doesn't seriously weaken the argument because it doesn't challenge the idea that higher average speeds would result from the new speed limits. It only states that "some" drivers wouldn't change their speeds, which could be a very small percentage of drivers. Thus, it doesn't significantly impact the conclusion.

b) Uniformity of speeds among vehicles is more important for highway safety than is a low average highway speed.

- This is the correct answer. If uniformity of speeds is more important for highway safety than a low average speed, then increasing speed limits might actually improve safety by making speeds more uniform. This directly challenges the conclusion that increasing speed limits would decrease highway safety.

c) Most drivers who drive 10 to 20 percent faster than current speed limits have never been involved in a highway accident.

- This answer choice doesn't weaken the argument because it doesn't address the impact of the new speed limits on highway safety. It only tells us about the current situation, not what would happen if speed limits were increased.

d) Some drivers who violate current speed limits would also violate higher speed limits.

- This answer choice doesn't weaken the argument because it actually supports the idea that higher average speeds would result from increased speed limits. It doesn't challenge the conclusion that increasing speed limits would decrease highway safety.

e) Most drivers who violate current speed limits determine their speeds by what they believe to be safe in the situation.

- This answer choice is irrelevant to the argument because it doesn't address the impact of increasing speed limits on highway safety. It only tells us about the decision-making process of drivers who currently violate speed limits, which doesn't help us determine whether the conclusion is valid or not.

In conclusion, the correct answer is B because it directly challenges the conclusion that increasing speed limits would decrease highway safety by introducing the idea that uniformity of speeds is more important for safety than a low average speed.