Logical Reasoning

PT124 · S2 · Q26 Editorialist: Some people argue that

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Editorialist: Some people argue that highway speed limits should be increased to reflect the actual average speeds of highway drivers, which are currently 10 to 20 percent higher than posted speed limits.

Conclusion

Increasing the speed limit 10-20% in order to better match the actual average driving speed of people would greatly decrease highway safety.

Evidence

Even though the people currently speeding would probably obey the new law, the people currently obeying the slower speed limit would increase their speed to the new, faster speed limit.

Evaluate

This author is making a Prediction, comparing what would be the case in this hypothetical Plan-World with what is the case in Current-World.

Predictions are always inherently comparisons, and with comparisons we think about other ways in which two things might be similar or different.

Current-World Plan World Speed limit 55mph 70mph

Rule drive drive breakers 70mph 70mph

Rule drive drive followers 55mph 70mph

Author's more highway less highway prediction safety safety

The only difference between the two worlds is that the law-abiding drivers speed up. So if we're fighting this argument, we're thinking,

Given That ... the law-abiding drivers will speed up, How Can We Argue That ... the highways won't be less safe?

Goal

The author is assuming that because we've increased the average speed of highway drivers, we've made things more risky (which is a reasonable assumption). We need to counter that effect by saying that something else matters to this prediction, or that something else will be different in Plan-World that will help highway safety.

26.

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

Some drivers who obey current
No Impact Too Weak: Some
This doesn't push back against anything the author said or thought. The author said that almost all all rule-following drivers who currently obey the limit will increase their speed. So she is already allowing for what this answer choice is saying. It's a very weak (and therefore unlikely-to-be-correct) idea that "at least one rule-follower will not increase their speed".
11% picked this
Correct
Uniformity of speeds among vehicles
Why this is right
This helps us make a very salient comparison between Current World and Plan World. In Current World, we have a lower average highway speed (a bunch of rule-following 55mph folk and a bunch of rule-breaking 70mph folk, for an average somewhere in the 62mph range). In Plan World, with a 70mph limit, the rule-followers and the (former) rule-breakers will be going 70mph, for an average somewhere in the 70mph range. But, in Plan World, there is greater uniformity of speeds among vehicles, since people are all going closer to 70mph. In Current World, the 70mph speeders are going much faster than the 55mph slowpokes, and so there is more irregularity to cars' speeds, and that weaving of fast cars past slower cars is creating hazardous situations. According to this answer, Plan World's higher uniformity of speed will outweigh Current World's lower average speed in terms of achieving highway safety. If Plan World seems safer than Current World, then we're pushing back against the author's conclusion that "in plan world, it would greatly decrease highway safety".
Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.
64% picked this
Most drivers who drive 10
No Impact
Since the "speeders", the ones currently going 70 in a 55, who will then go 70 in a 70mph zone if the new limit goes into effect, are driving the same speed in both Plan World and Current World. Since their behavior isn't changing in this hypothetical world, we don't really get any value of learning about them (unless we're told that their behavior would change somehow in Plan World).
8% picked this
Some drivers who violate current
No Impact Too Weak: Some
This doesn't push back against anything the author said or thought. The author said that most drivers who currently speed over the limit will obey the new speed limit. So by using that quantifier, she is already allowing for what this answer choice is saying. It's a very weak (and therefore unlikely-to-be-correct) idea that "at least one current speeder will end up also speeding over the new, faster limit".
5% picked this
Most drivers who violate current
Unclear Impact
The speeders (the ones who currently break the 55mph limit but most of whom would obey the higher speed limit) are essentially driving the same speed in both Plan World and Current World. Unless their behavior is changing in this hypothetical world, we don't really get any value of learning about them. This answer doesn't make it clear whether they would deem things more/less safe in Plan World, so we can't tell if they would behave differently or in which direction that difference would go.
11% picked this

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