LSAT Explanation PT 20, S4, Q3: Opponents of allowing triple-trailer trucks to

LSAT Question Stem

Which one of the following, if true, most substantially weakens the argument? 

Logical Reasoning Question Type

This is a Weaken question. 

Correct Answer

The correct answer to this question is B. 

LSAT Question Complete Explanation

Let's first analyze the argument in the passage. The argument states that opponents of allowing triple-trailer trucks on the national highway system are wrong in claiming that these trucks are more dangerous than other commercial vehicles. The premise given is that in the western part of the country, where triple-trailers are allowed on some highways, the rate of road accident fatalities per mile of travel for these vehicles is lower than the national rate for other types of commercial vehicles. The conclusion drawn from this premise is that triple-trailers are safer than other commercial vehicles.

To better understand this argument, let's use a simple example. Imagine a small town where bicycles are allowed on certain roads, and the rate of bicycle accidents is lower than the national rate for car accidents. From this information, the argument would conclude that bicycles are safer than cars.

Now, let's come up with an "Evaluate" question for the argument: Are there any factors specific to the western part of the country that could affect the rate of road accident fatalities for triple-trailers?

The question type for this problem is Weaken, which means we need to find an answer choice that weakens the conclusion drawn from the given premise.

a) This answer choice discusses the weight capacity of triple-trailers compared to smaller semitrailers, which is not relevant to the safety of triple-trailers. It does not weaken the conclusion.

b) This answer choice provides a reason for the lower rate of road accident fatalities in the western part of the country, stating that highways there are less heavily traveled and safer than highways in the national system as a whole. This weakens the conclusion because it suggests that the lower rate of fatalities for triple-trailers might be due to the safer highways, rather than the inherent safety of the trucks themselves. This is the correct answer.

c) This answer choice mentions that opponents of triple-trailers also once opposed shorter twin-trailers, but this information does not affect the safety comparison between triple-trailers and other commercial vehicles. It does not weaken the conclusion.

d) The fact that drivers need a special license to operate triple-trailers in areas where they are permitted does not provide information about the safety of the trucks themselves. It might suggest that the drivers are more skilled or knowledgeable, but it does not directly weaken the conclusion about the inherent safety of triple-trailers compared to other commercial vehicles.

e) This answer choice provides information about the rate of road accident fatalities for triple-trailers in different years, but it does not compare these rates to those of other commercial vehicles. It does not provide information that weakens the conclusion.

In conclusion, the correct answer is B, as it provides an alternative explanation for the lower rate of road accident fatalities for triple-trailers in the western part of the country, weakening the argument's conclusion that triple-trailers are safer than other commercial vehicles.