If the main city thoroughfare is restricted to commercial

What if you negated C. Is it breaking down the conclusion. Also while Assumption, you can not ignore something like you did here. What if there are no such vehicle as more then 2 ton. Remember you have to consider all the possibilities.

I think the Answer should be D.

E seems out of scope, since we cannot assume two facts. In E it seems we are assuming Commercial vehicles are causing traffic congestion & the traffic congestion is causing accidents.

However in D, we can clearly see that, since Commercial vehicles are made to bypass the city & use the city highway, they are the only ones out of the roads in the city. The argument concludes that such a reduction (reduction of commercial vehicles from city roads) will significantly reduce accident rates (hinting that commercial vehicles were contributing significantly to accident rates prior to their removal). Hence the assumption that Commercial have a greater risk of becoming involved in accidents.


Thanks,
GyM

Premise:
If the main city thoroughfare is restricted to commercial vehicles weighing less than 2 tons, most of the commercial traffic would be forced to bypass the city using the city highway.

Conclusion:
Such a reduction in traffic will significantly reduce accident rates in the city.

Assumption is always the gap between premise and Conclusion. Such as in this case you don't need to read option E to tell it is assumption. read these two and you can fill the gap with assumption on your own. higher congestion is the one author want to reduce .Hope that helped.

Before we reach that point, lets assume two situations for the sake of our discussion: (a) most of commercial vehicles plying are less than 2 tons or (b) most of the commercial vehicles plying are more than 2 tons.

The author mentions that "If the main city thoroughfare is restricted to commercial vehicles weighing less than 2 tons, most of the commercial traffic would be forced to bypass the city using the city highway." Note that the word used is "most".

Lets pause here and analyze under which situation would "most of the commercial traffic would be forced to bypass the city"? If the ban is on vehicles more than 2 tons, but there are very few such vehicles (situations [a] above), then how can "most" of the traffic be forced to bypass the city???

Clearly, this is possible only under situation (b) - where most of the commercial vehicles plying are more than 2 tons.

We need to agree till this point at least to move forward...

The conclusion drawn above depends on which of the following assumptions?


A. City highway would be as convenient as the main city thoroughfare for the vehicles that are forced to use the highway.

Convenient is out of scope.

B. Private vehicle drivers are more careful than commercial vehicle drivers and hence can be allowed to drive on the main city thoroughfare.

Private vehicle is out of scope.

C. Most traffic today consists of commercial vehicles weighing more than 2 tons.

We cannot assume that most traffic leads to accidents. So C is out.

D. Commercial vehicles have a greater risk of becoming involved in accidents.

Commercial vehicles less than 2 tons may also lead to accidents. So D is out.

E. Higher traffic congestion leads to higher risk of accidents.

Finally, I go with E.



Sent from my ONE A2003 using GMAT Club Forum mobile app

The conclusion states that by diverting commercial traffic, the resulting decrease in traffic will lead to decrease in accident rates.

D and E are close. But nowhere is it hinted that accidents are caused by the commercial vehicles or commercial vehicles are necessarily "involved" in accidents or accident rates have commercial vehicles involved in the majority of them. Hence, E.

Hey aragonn,
The gap is most of the time between premise and conclusion but here i think the gap is in the conclusion itself. The gap that links traffic to accident rates. Am I right?

The statement in red does not accurately reflect the negation of C.
most = more than 50%.
In C, the term most refers not to commercial traffic but to TRAFFIC TODAY.
C, negated:
MOST TRAFFIC TODAY does not consist of commercial vehicles weighing more than 2 tons.
Here, it is possible that 50% of traffic today is composed of vehicles weighing more than 2 tons.
Implication:
Banning these vehicles would significantly reduce traffic, leaving the conclusion of the argument intact.
Since the negation of C does not invalidate the conclusion, eliminate C.

I am not sure what you mean by that "gap in conclusion." Can you please clarify it.
More often you have to keep the situation simple. keep it this way for starters, think of two sentences and ask your self that what are the possible cases in which this conclusion can come out. usually one of them will be a gap. with practice you find it more often. Also negation test is very important.

Dear GMATGuruNY,

1- Could the negations of 'C' consider STRENGTHENING the conclusion?

2- Could the negation of 'D' be

Commercial vehicles have a low risk of becoming involved in accidents.

or

Commercial vehicles do not have a greater risk of becoming involved in accidents.

3- In either case, Does negation of 'D' WEAKENING the conclusion? So 'D' could be an assumption. Does not the argument use the commercial vehicles less than 2 tons to conclude that it is responsible for traffic and hence accidents?

Thanks

Hey aragonn,
I mean that there is a missing link that connects the two ideas together (traffic to accident rates).
Normally the missing link is between the premise and the conclusion but in this example it was the conclusion itself. Right?

Great observation, here is the missing link ....


Commercial traffic bypassing the city -----------Reduction in accident rate.

Only option (E) bridges the gap between Reduced traffic congestion and accident rates, hence our answer must be (E)

A. City highway would be as convenient as the main city thoroughfare for the vehicles that are forced to use the highway. - Totally Irrelevant because the argument doesn't talk anything about convenience

B. Private vehicle drivers are more careful than commercial vehicle drivers and hence can be allowed to drive on the main city thoroughfare. - The cause of problem is congestion and not private vehicles, hence it goes out of scope of the question

C. Most traffic today consists of commercial vehicles weighing more than 2 tons. - This choice can be inferred from the passage. if most of the heavy vehicles (>2 ton) would need to bypass using the highway

D. Commercial vehicles have a greater risk of becoming involved in accidents. - This is out of scope of argument as the argument tries to maintain a connection between accidents and congestion, not about the type of vehicles and accidents

E. Higher traffic congestion leads to higher risk of accidents. - This is unstated in the argument and best of all possible options

KarishmaB MartyTargetTestPrep ExpertsGlobal5

Not sure why, but I can not get my head to accept E as the correct answer. Here is my explanation below:

Assuming a traffic of 100 vehicles, out of 5 are commercial vehicles >2tonnes and other vehicles 95 in number.
Now considering option E, even if we negate it - "Higher traffic congestion does not lead to a higher risk of accidents; the conclusion "such a reduction in traffic(reduction of 5 Heavy commercial vehicles)will significantly reduce the accident rates because the heavy commercial vehicles, though small in number will significantly reduce it.

But for option C, if we negate the option - commercial vehicles do not have greater risk for getting involved in accidents, then we can not say their reduction will significantly reduce accident rates.
Option E would have been correct if it mentioned "Commercial traffic congestion" instead of just "traffic congestion".

Plz. let me know where my thinking is wrong.
For me option D looks more appropriate.

Hi shanks2020.

This question is not particularly well written. The conclusion is simply that a reduction in traffic will result in a reduction in accident rates. There's actually no support for that conclusion in the passage. So, identifying an assumption upon which the argument depends doesn't really make sense.

However, we can presume that what the argument is meant to be is that there will be a reduction in traffic, and that therefore there will be reduction in the rates of accidents.

Then, we can look for an assumption upon which that argument depends.

In that case, (D) is not a necessary assumption. After all, even if it is not the case that "commercial vehicles have a greater risk of becoming involved in accidents," it could still be the case that a reduction in traffic will result in a reduction in accident rates.

On the other hand, that argument does depend on (E) because, if it's not true that "higher traffic congestion leads to higher risk of accidents," then it doesn't make sense to conclude that a reduction in traffic will result in a reduction in the rates of accidents.

So, the best answer is (E).

I do have general question regarding negation in assumptions
when we do negation does it has to doubt the conclusion or completely breakdown