LSAT Explanation PT 38, S4, Q14: Reducing speed limits neither saves lives

LSAT Question Stem

The argument's reasoning is flawed because the argument 

Logical Reasoning Question Type

This is a Flaw question. 

Correct Answer

The correct answer to this question is D. 

LSAT Question Complete Explanation

Let's first analyze the argument in the passage. The passage states:

1. Reducing speed limits neither saves lives nor protects the environment. (Conclusion)

2. The more slowly a car is driven, the more time it spends on the road spewing exhaust into the air and running the risk of colliding with other vehicles. (Premise)

The argument's conclusion is that reducing speed limits doesn't save lives or protect the environment. The premise supporting this conclusion is that driving more slowly leads to cars spending more time on the road, which increases exhaust emissions and the risk of collisions.

To make this more relatable, imagine you're walking through a room filled with balloons. The faster you walk, the less time you spend in the room and the fewer balloons you might accidentally pop. The slower you walk, the more time you spend in the room, and the more likely you are to pop balloons. The argument is suggesting that reducing speed limits is like walking slowly through the balloon-filled room, resulting in more popped balloons (accidents and pollution).

An "Evaluate" question for this argument could be: "Does the speed at which a car is driven have a greater impact on exhaust emissions and collision risk than the time spent on the road?"

Now let's discuss the question type and answer choices. The question type is a Flaw question, asking us to identify the flaw in the argument's reasoning. We'll go through each answer choice and analyze them.

a) neglects the fact that some motorists completely ignore speed limits

- This answer choice doesn't address the argument's reasoning and doesn't undermine the conclusion. Even if some motorists ignore speed limits, it doesn't affect the argument's claim about the relationship between driving speed, time spent on the road, and the consequences of reducing speed limits.

b) ignores the possibility of benefits from lowering speed limits other than environmental and safety benefits

- The argument's conclusion is specifically about saving lives and protecting the environment. This answer choice is out of scope because it introduces benefits unrelated to the conclusion. It doesn't address the reasoning flaw in the argument.

c) fails to consider that if speed limits are reduced, increased driving times will increase the number of cars on the road at any given time

- This answer choice doesn't address the flaw in the argument's reasoning. In fact, it seems to support the conclusion that reducing speed limits doesn't save lives or protect the environment.

d) presumes, without providing justification, that total emissions for a given automobile trip are determined primarily by the amount of time the trip takes

- This answer choice correctly points out the flaw in the argument's reasoning. The argument assumes that the amount of time spent on the road is the primary factor determining total emissions, without considering other factors such as the speed of the car or the type of car. This flaw calls into question the validity of the conclusion.

e) presumes, without providing justification, that drivers run a significant risk of collision only if they spend a lot of time on the road

- This answer choice is incorrect because the argument doesn't make the assumption that drivers run a significant risk of collision only if they spend a lot of time on the road. The argument simply states that spending more time on the road increases the risk of collision, but it doesn't limit the risk to only this factor.

The correct answer is D, as it accurately identifies the flaw in the argument's reasoning.