Urban rail systems have been proposed to alleviate traffic congestion,

Problem: Traffic congestion (too may cars on the roads)

Debate between supporters and opposers of Urban Rail:

Supporters of Urban Rail: Urban Rail reduces congestion.

Opposers of Urban Rain: Not effective. In a city, when employment increased by 96,000, there was a decline of 3100 commuters (people who travel to and fro office every day). So urban rail did not reduce congestion.

Supporters of Urban Rail: Commuter trips represent just 20% of travel in that city. (The commuter trips are not the main source of congestion. Perhaps other 80% cause congestion and they have been using the urban rail and hence reducing congestion. So reduction in commuter trips doesn't say much about whether rails are effective. So if one small fraction isn't using the urban rails much, it doesn't matter. Perhaps others are using and hence traffic is lower)

What will criticise this response of supporters?

A) presents no evidence to show that the statistics are incorrect

The statistics needn't be incorrect.

B) relies solely on general data about U.S. cities rather than data about the city in question

It does talk about that city.

C) fails to consider that commuting trips may cause significantly more than 20 percent of the traffic congestion

Correct. The supporters are supporting - "Urban rail reduces congestion."
Now, what if most of the congestion is caused by commuters even though commuter travel is just 20% of travel? What if the morning and evening office times are the times of congestion because the roads cannot handle so much commuter traffic. The other travel could be staggered around the day causing no congestion. Then if commuters are not using urban rail, it doesn't help in reducing congestion.
Commuters may not be a big part of the total travellers but they could be the whole and sole cause of the congestion problem.

D) fails to show that the decline in the number of urban rail commuters in one U.S. city is typical of U.S. cities generally

Not correct. The opposers cited the example of one city and the supporters are presenting evidence in the case of that city itself.

E) provides no statistics on the use of urban rail systems by passengers other than commuters

Not correct. They are providing an explanation for why the commuters data given by opposers is not relevant. The opposers talked about commuters.

Answer (C)
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Urban rail systems have been proposed to alleviate traffic congestion, but results in many cities have been cited as evidence that this approach to traffic management is ineffective. For example, a U.S. city that opened three urban rail branches experienced a net decline of 3,100 urban rail commuters during a period when employment increased by 96,000. Officials who favor urban rail systems as a solution to traffic congestion have attempted to counter this argument by noting that commuting trips in that city represent just 20 percent of urban travel.

The response of the officials to the claim that urban rail systems are ineffective is most vulnerable to criticism on the grounds that it

URS is proposed to ease traffic congestion but there are cities which prove otherwise. Further a data is presented that a city with three branches of UR had decline in number of commuters whereas, on the other hand, employment had increased.
To this officials favoring URS as a solution counter by saying that commuting trips by people is just 20% of urban travel.

Since nothing else is given in the passage we can say that officials thought that their reasoning is enough to counter the result presented earlier or in other words they assumed that URS commuting is just 20% of the total travel and that possibly is not enough to ease the congestion caused by other 80% travel. So, in a way, officials safeguard their side of argument.
Now, let's look into the options:

A) presents no evidence to show that the statistics are incorrect - WRONG. A possible candidate only if other options are eliminated using POE. For it to be picked up as the right answer a bridging assumption is required which is wrong to make and again leads to POE method.

B) relies solely on general data about U.S. cities rather than data about the city in question - WRONG. Goes against the argument. Its the opposite - a city's data is given as an example to prove a general trend of many cities.

C) fails to consider that commuting trips may cause significantly more than 20 percent of the traffic congestion - CORRECT. What if people use private vehicles to reach the URS either home to URS or office to URS and vice-a-versa. In that case it would have significantly increased the percentage.

D) fails to show that the decline in the number of urban rail commuters in one U.S. city is typical of U.S. cities generally - WRONG. Irrelevant actually. Its not important.

E) provides no statistics on the use of urban rail systems by passengers other than commuters - WRONG. Again it goes off-track. Even if officials had provided it would not have had any role in proving the point that officials were defending URS.

IMO Answer C.
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TARGET: Find flaw in the reasoning of officials

A)why should he prove stats wrong? Irrelevant

B)So ? an example need not be the model in discussion and still be valid

C)He said C trips=only 20% of urban trips . But 20% of urban trips may be > 20% of congestion.He did miss this point ,lets keep this.

D)Why should he show the whole US as an example ? even a single city serves as a good example.

E) Ok, let's say if he mentioned URS-psngrs stats...then...? still can't fix the flaw with this., i.e the decline of commuters(3100) with comparatively huge increase in employment(96000)

Therefore OA:C


Don't fall for common GMAT trap relevance of words: option E is a trap . it has few words from info doesn't mean its answer. Verify clearly to declare a contender

Thanks.
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Flaw: 20% of urban travel does not necessarily means 20% of total traffic congestion, an insignificant contribution.
May be, most of the remaining 80% urban travelers are already using URS and thereby are insignificant contributors to traffic congestion whereas, infact these 20% commuters are causing the congestion.

Hence, Choice C.

Choice A: Argument does provide an alternate statistical evidence to counter but this evidence is flawed.

GMATNinja

I chose D thinking that if one city is representative for all other cities, the argument is good and D clearly states that the officials failed to establish such reasoning.

Could you explain why C is correct and not D ?

Thanks,
K

Can someone please explain the last sentence "Officials who favor urban rail systems as a solution to traffic congestion have attempted to counter this argument by noting that commuting trips in that city represent just 20 percent of urban travel." in the light of the argument. I can't seem to get my head around the last sentence.

VeritasKarishma

Can you pls explain how is choice C addressing the weakness in argument

There is extra effort required in such questions where question stem uses complex language.
Let's breakdown the question first-
The response of the officials to the claim that urban rail systems are ineffective is most vulnerable to criticism on the grounds that it-
The response of the officials to the claim that urban rail systems are ineffective- What is the response of officials ?
So as per officials"commuting trips in that city represent just 20 percent of urban travel.", hence to claim urban rail systems are ineffective is wrong.

Next part of question- is most vulnerable to criticism on the grounds that it
Thus we have to show that official reasoning is flawed and urban rail systems are actually ineffective.

Let's look at options:

Evidence here is unrelated.It is a fact that city represent just 20% of urban travel and hence evidence not required.
This option doesn't solve our purpose.

Official never mentioned any data from other US cities.This option is irrelevant.

Interesting option as it forced us to think.
As per this option, there are chances that most congestion is caused by those 20% commuters only. Maybe those 20% commuters caused 100% congestion.
Thus official quoting that city represents only 20% of urban travel is in big trouble here
Keep it till we find something better.

typical means-representative as a symbol; symbolic.
Now why official want to represent a city,where there is decline in urban rail commuters,as a symbol ?

Official talks only about commuters and we don't know about congestion contribution of other passengers.
Hence this option is wrong.
Option C is correct.

Hi VeritasKarishma

In option E, the remaining 80% of the travel can cause congestion, which the proponent has not talked about. Hence, even if commuters form only 20%, the remaining 80% can cause congestion, and hence bringing them to rail would release congestion. Or he tries to justify the usefulness by commenting only on 20% of the total travel, which is wrong. Why isn't option E correct then?

We have to criticise the response given by supporters. Supporters have responded to what opposers had said.
The criticism of the response will be that the response may not give an accurate picture. The criticism will not be that the supporters should have given more points in support. We have to say why what they said is not an accurate representation.

Supporters of Urban Rail: Urban Rail reduces congestion.

Opposers of Urban Rain: Not effective. In a city, when employment increased by 96,000, there was a decline of 3100 commuters. So urban rail did not reduce congestion.

Supporters of Urban Rail: Commuter trips represent just 20% of travel in that city.

We have to say why this figure of 20% may not represent the actual picture.

E) provides no statistics on the use of urban rail systems by passengers other than commuters

This says that they are not telling us more about the 80% non commuters and about who is using the rails. We don't have to worry about that. We cannot decide how they choose to support rails. We have to criticise what they are actually saying.

Opposers said that fewer commuters are using rails. So rails are not helpful. Supporters said that commuters are just 20% of travellers. But, what if these 20% are responsible for all the congestion? Then supporters logic of "just 20%" is not good enough. This is what (C) says.

Hence answer is (C)
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A) presents no evidence to show that the statistics are incorrect
- Incorrect. There is no such rule :D

B) relies solely on general data about U.S. cities rather than data about the city in question
- Incorrect. the data given by officials is for the city in discussion only.

C) fails to consider that commuting trips may cause significantly more than 20 percent of the traffic congestion
Correct. If we consider that commuter trips cause > 20% congestion, then we can say that the opening of three rail branches may have not reduced the congestion.

D) fails to show that the decline in the number of urban rail commuters in one U.S. city is typical of U.S. cities generally
- Incorrect. An example is being discussed; universal applicability is not an issue.

E) provides no statistics on the use of urban rail systems by passengers other than commuters
- Not true. If 20% are commuters, then 80% are, automatically, "others".

C is the correct option.

sharing an excerpt from OG explanation-

"...if noncommuters typically use the rail system, commuting might even constitute most of the car traffic in the city. So a net movement of commuters from rail travel to car travel could be detrimental to the goal of alleviating traffic congestion even if a minority of urban travel is in the form of commuting."

I am not able to understand the reasoning presented above, especially the bolded portions. However, I do get that how 20% commuters can disproportionately contribute to traffic congestion.

VeritasKarishma, May I request your guidance here?

BhaveshGMAT -
Take OG explanations with a grain of salt. Rely on explanations on forums such as this one.
Without context of the two lines you have given above, I am unable to make out what this is referring to.
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KarishmaB here is the context can you pls explain the reasoning used? Not clear on the entire reasoning and especially the bold parts. Also not very clear on the reasoning on the thread as I still do not get how the supporter is justifying himself by stating that 20% of the urban travel is by commuter trip. Even if he thinks so, what is he presuming really to even think it matters because in any case there is still a NET DECREASE in ppl traveling by rail.
Commuters =C, Non commuters = NC;
C+NC= Total
Total old > Total new and since there is overall a net decrease in people traveling by rail thus NC has either decreased or increased by an amount less than the decrease in C old such that Total old < Total new. We have no reason to think they is an overall increse as stated in the explanation below nor do we have a reason to assume that NC has increased as you have stated in your explantion. Please clarify.

avigutman ThatDudeKnows KarishmaB MartyTargetTestPrep

Reasoning Which answer choice most undermines the officials’ response to the claim that
urban rail would be ineffective in relieving urban traffic congestion?
Theoretically, urban rail service should help reduce traffic congestion by
encouraging people to travel by train instead of by car. However, there is
purported evidence that this approach is ineffective: In at least one city, an
increase in the availability of rail service correlated with a decrease in the
number of commuters traveling by rail, even though the total number of
commuters apparently increased. Some officials object that in that city,
commuters account for only 20 percent of urban travel. The officials’ point is
presumably that even if there was a net decline in commuters using the rail
system, there may have been an overall increase in the number of people who
used rail instead of driving. However, the stated goal of building more rail
systems is to reduce traffic congestion, not just to reduce the overall amount of
urban car traffic. Even if commuting makes up only 20 percent of urban travel
in the city in question, it might contribute disproportionately to traffic
congestion, and if noncommuters typically use the rail system, commuting
might even constitute most of the car traffic in the city. So a net movement of
commuters from rail travel to car travel could be detrimental to the goal of
alleviating traffic congestion even if a minority of urban travel is in the form of
commuting.

The net decrease is NOT in ppl traveling by rail, Elite097. The problem with the reasoning of the officials who favor urban rail systems as a solution to traffic congestion is that they're conflating traffic congestion and urban travel. It's possible that 20% of urban travel causes 80% of traffic congestion - that's a vulnerability of the official's argument.
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Total old is NOT greater than total new.
There is NOT a net decrease in people using the rails. There is decrease of 3100 in the number of "commuters." These are the people who travel to work (employment purposes) every morning and evening. There are other travellers (people travelling to buy home supplies, visiting friends, going to restaurants etc). We don't know whether the total number of people using the rails has increased or decreased.

The aim of the plan is to reduce "congestion," not "traffic."
Who causes congestion? What if the commuters are responsible for congestion? Say every morning between 8 to 10 AM and evening 5 to 7 pm there is huge congestion on city roads because of commuters (people going to and coming from office). At all other times, there is traffic but no congestion - traffic is free flowing (of other travellers). So commuters may represent only 20% of all day traffic but may be responsible for all the congestion (in the morning and the evening).
When supporters claim that only commuter numbers are meaningless because commuters are only 20% of all traffic, what they ignore is that commuter numbers may be the ones mostly responsible for congestion. The aim is not to reduce number of vehicles on the road; the aim is to reduce congestion i.e. reduce number of vehicles when many vehicles are together on the road.

So consider a scenario before rails -
Rush hour in morning and evening (congestion) while the whole day traffic is heavy but flows smoothly (no congestion).

With rails -
Rush hour in morning and evening (congestion - commuters are not using rails) while the whole day traffic is light because people are using rails.

Were we able to reduce congestion with rails? No.
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Hi experts,

Does the current GMAT still employ questions similar to this one?? They are really hard to grab the flow of reasoning, not to mention the tricky in word choices and terms.

This question showed up in the most recent edition of the Verbal Review guide, so there's no reason why you couldn't see something like it.

Of course, every question is different, so you're not going to see a question whose logic is identical to this one. So don't agonize too much over the details here. If your overall performance is good, you're in good shape. This particular question is pretty tough, so if you struggle on this one, you're not alone.

I hope that helps a bit!
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did this one in 10 mins , but got correct huh ! definitely a tough one .