#14 - Reducing speed limits neither saves lives nor protects

[voodoochild]

Teachers,
I am not sure why A) is incorrect.

I feel that A) hinges on a minor gap in the argument :

Premise talks about "more slowly a car is driven .... " but the conclusion is about "reducing speed limit ". I feel that A) is trying to attack this gap. Essentially, just because the speed limits are reduced, the drivers won't have an incentive to drive slowly. If there are some drivers (In LSAT World, some means at least 1 - hence, "some" could mean all) don't follow speed limts. (In fact, I don't follow speed limits every time:))

I am not sure why A) is incorrect in such a case. Please help me

Thanks

[Nikki Siclunov]

The argument only concerns those who obey the speed limit, i.e. those who reduce drive more slowly because of the reduced speed limits. If some motorists ignore speed limits, this would only support the conclusion that reducing speed limits is essentially pointless.

The flaw in the argument is the assumption that the length of the trip is the primary factor determining the amount of pollution and the level of risk caused by the vehicle. If some other factor were more important (i.e. how fast the car is driven), the conclusion would be weakened. This is why answer choice (D) is correct: it states an unwarranted assumption upon which the argument depends.

[sotor26]

Hello,

I took the Logical reasoning (part II) of the October 2002 and had some questions regarding some of the answers:

14. This a flaw in reasoning argument but I have no idea how they came to the conclusion that D was the correct choice.


Thank you so much! Any input would be great!!!

[Steve Stein]

Hi,

That's a good question—and you alluded to an important point: Sometimes the right answer choice cannot be prephrased very precisely. In this case the author argues reducing road speeds doesn't help protect people or the environment, based on the fact that a longer time spent on the road means more risk and more exhaust-spewing. What's the issue? The author doesn't consider the possibility of greater overall efficiency or risk-reduction. Only answer choice (D) describes an issue with this argument: It presumes without basis that time spent on the road is the primary determinant of total emissions (and doesn't consider the possibility that going faster might mean less time on the road but more exhaust overall.

I hope that's helpful! Please let me know whether this makes sense--thanks!

Steve

[sotor26]

Hello,

Thank you! I completely skipped over the flawed relationship that the author states! Thank you for pointing it out!

[LSATer]

Is the problem with E, the phrase "only if?" If the word "only" was removed from the answer choice, and it read "presumes, without providing justification, that drivers run a significant risk of collision if they spend alot of time on the road, " would it be right?

Thank you,

LSATer

[Jonathan Evans]

Hi, LSATer,

You're on the right track. However, that wouldn't even quite get you there. It is not wholly unjustifiable to think that time spent on the road is correlated with the risk of getting in an accident. After all, if you're not on the road, it would be reasonable to assume that you're not likely to get into an automobile accident (one would like to think! ).

Instead the characteristic of (D) that makes it the credited response rather than (E) has to do with the relative weight of different factors in determining safety or environmental harm. The premises state (in an incontrovertible manner) that time spent on the road does correlate with accident risk, but the author does not provide sufficient evidence that there is no mitigating factor or benefit of lower speeds that would outweigh the increased time on the road.

The issue is relative importance and no other factors, not that the factors the author identifies are of no importance. Time on the road and time in a car do have something to do with environmental harm and accident risk, respectively, but they need not be the only factors. I hope this helps!

[bk1111]

Hi, I chose D by process of elimination, but I was hesitant about D because the AC says "primarily" ... I did not think the stimulus warranted saying total emissions are primarily determined by the amount of trips. Can someone elaborate on why it works in this situation?

[Francis O'Rourke]

There is a lot unsaid in this argument. We can infer that the speaker is presuming that time is the primary factor, since their argument would be severely weakened if there were some other, more important factor. It simply would not make sense to believe that the more time you spend driving equals the more exhaust you spew, if you thought that there were more important factors that go into the amount of exhaust a car emits.

As Nikki said above:

if some other factor were more important (i.e. how fast the car is driven), the conclusion would be weakened. This is why answer choice (D) is correct: it states an unwarranted assumption upon which the argument depends.

[akanshalsat]

Hey!

I feel like D and E are quite similar as they are relating time to each one of the things discussed in the stimulus. I chose E, but I understand why D is correct HOWEVER, i'm confused as to why I should be choosing D over E? What is the difference? why is D correct?