The faster a car is traveling, the less time the driver

Question

The faster a car is traveling, the less time the driver has to avoid a potential accident, and if a car does crash, higher speeds increase the risk of a fatality. Between 1995 and 2000, average highway speeds increased significantly in the United States, yet, over that time, there was a drop in the number of car-crash fatalities per highway mile driven by cars.

Which of the following, if true about the United States between 1995 and 2000, most helps to explain why the fatality rate decreased in spite of the increase in average highway speeds?

(A) The average number of passengers per car on highways increased.

(B) There were increases in both the proportion of people who wore seat belts and the proportion of cars that were equipped with airbags as safety devices.

(C) The increase in average highway speeds occurred as legal speed limits were raised on one highway after another.

(D) The average mileage driven on highways per car increased.

(E) In most locations on the highways, the density of vehicles on the highway did not decrease, although individual vehicles, on average, made their trips more quickly.

GMATPrep Code  :  VCR005853

Hi, I chose (E). Can anyone explain why it is not the right choice, please.
OE is not clear to me. Thanks.

KarishmaB · Accepted Answer

Responding to a pm:

Premises:
- Faster a car, more is the risk of fatality.
- In a span of 5 yrs, avg highway speed increased.
- In the same time, number of car-crash fatalities per highway mile driven by cars reduced.

Say, per year, the total number of highway miles driven by all cars is 1000. Say, there are 10 cars and each drives 100 miles every year on the highway.
If there were 10 fatalities, number of car-crash fatalities per highway mile driven by cars = 10/1000 = 0.01

Assuming everything same, if speed of cars increase substantially, expected number of fatalities increases. Say it becomes 20.
So number of car-crash fatalities per highway mile driven by cars = 20/1000 = 0.02
This is what is expected.

Oddly, this number actually went down. (B) tells you that this was because people were more careful and cars were better. So number of fatalities went down. Fair enough.

(D) The average mileage driven on highways per car increased. 
Avg mileage driven on highways per car was 100 miles in our previous case.
Say, avg mileage driven on highways per car increases to 200 miles now. 
More miles are driven (assuming number of cars is same) but this indicates that number of fatalities will also increase. From 10, we might see 20 fatalities. This option does not imply that number of fatalities will remain the same i.e. at 10. 
Or think of it another way - there is a certain number of fatalities per highway mile driven say 0.01. It doesn't matter how many miles were driven exactly. This only implies that if 100 miles were driven, there was one fatality. If 1000 miles were driven, there were 10 fatalities. If 10000 miles were driven, there were 100 fatalities. The fact that people have started driving more does not increase/reduce this number.

shreister · Answer

This is the sort of question, you can estimate the answer before looking at the choices. the Q says the avg. speed on the highway has increased but with a reduction in the number of fatalities/ highway mile. What could be the reasons? 1. better safety equipment installed. 
A is wrong. it should be the other way around.
B is exactly what you are looking for.
C is irrelevant. we are not asked why the highway speeds increased
D also is not explainign anything.
E says that the density of vehicles remained same and individual vehicles increased their speed. This explains the higher avg speed of the cars but not the reeduction in fatalities.

B is the only option

plumber250 · Answer

Hi, Let me see if I can help.

What is the question saying:

If all else is equal faster cars = more deaths

BUT cars in America travelled faster, and there were less deaths.

We need to solve that puzzle.

First up - use a bit of logic. What do you know about Cars and safety over time? It's pretty well known that car safety improved. That's a good indicator of something to look for.

B provides exactly that - a reason why people crashing at high speeds may actually be better protected than we would expect. It is the correct answer

As for E, does it help you answer the puzzle? No - it gives no reason why cars in crashes would be better/worse off. It's irrelevant to the question

Hope that helps.

James

souvik101990 · Answer

The faster a car is traveling, the less time the driver has to avoid a potential accident, and if a car does crash, higher speeds increase the risk of a fatality. Between 1995 and 2000, average highway speeds increased significantly in the United States, yet, over that time, there was a drop in the number of car-crash fatalities per highway mile driven by cars.

Which of the following, if true about the United States between 1995 and 2000, most helps to explain why the fatality rate decreased in spite of the increase in average highway speeds?

(A) The average number of passengers per car on highways increased. 
(B) There were increases in both the proportion of people who wore seat belts and the proportion of cars that were equipped with airbags as safety devices. 
(C) The increase in average highway speeds occurred as legal speed limits were raised on one highway after another. 
(D) The average mileage driven on highways per car increased. 
(E) In most locations on the highways, the density of vehicles on the highway did not decrease, although individual vehicles, on average, made their trips more quickly.

dinesh86 · Answer

The faster a car is travelling, the less time the driver has to avoid a potential accident, and if a car does crash, higher speeds increase the risk of a fatality. Between 1995 and 2000, average highway speeds increased significantly in the United States, yet, over that time, there was a drop in the number of car-crash fatalities per highway mile driven by cars.

Which of the following, if true about the United States between 1995 and 2000, most helps to explain why the fatality rate decreased in spite of the increase in average highway speeds?

(A) The average number of passengers per car on highways increased - In this case, Fatalities should have increase instead of decreasing.
(B) There were increases in both the proportion of people who wore seat belts and the proportion of cars that were equipped with airbags as safety devices - Correct. Both factors would have decreased the chances of fatalities
(C) The increase in average highway speeds occurred as legal speed limits were raised on one highway after another - Same as A.
(D) The average mileage driven on highways per car increased - Irrelevant
(E) In most locations on the highways, the density of vehicles on the highway did not decrease, although individual vehicles, on average, made their trips more quickly - OFS

Kudos please....

unparadise · Answer

Hi everyone,

I want to make sure that I understand why option D is incorrect. My assumption is fatality rate/per mile is calculated by divide the total fatality number by the total miles driven. If my assumption is correct. Then given that average miles driven per car increased, the total miles driven would increase as well. Going back to the formula for fatality rate/per mile, if the total fatality number has not increased but the total miles driven has, then the fatality rate/per mile would decrease.

If my logic wrong when I assumed that the total fatality number stayed the same?

Thanks,
Frank

manishkhare · Answer

Hello unparadise  ,
Fatality rate calculation per mile is not applicable here.

The passage says : accidents have increased and fatality rate has gone down .
What can be derived from this conclusion .
Cars have becomes better .They have more safety features.

Now look at the options : 
Option B says:There were increases in both the proportion of people who wore seat belts and the proportion of cars that were equipped with airbags as safety devices.

This is the only option which explains the paradox.

truongynhi · Answer

Hi Karishma,

How could we know that the fatality rate (or the number of fatalities) will increase proportionally with the increase in mileage driven?

In my flawed reasoning, I just simply put the increased denominator, which is the mileage driven (assuming the same number of cars), in the rate formula and consequently concluded that fatality rate increases.

Please correct me. Really appreciate your help.

KarishmaB · Answer

The point is that fatality rate per highway mile driven does not change if the number of miles driven increases. It is something like this:

Say my speed is 60 miles/hr. I maintain this speed. Does it matter whether I drive for 2 hours at this rate or 4 hours at this rate? Will my speed change if I drive more? No, right? When I drive for more hours, the distance I covered increases.

Similarly, fatality rate per highway mile is a rate which will not change with the change in the number of highway miles driven. If more highway miles are driven, the number of fatalities increase.

AryamaDuttaSaikia · Answer

This is a paradox question. The average highway speed increased and high speed ideally should lead to higher number of fatalities; yet the number of fatalities was less. Why is that so? It has no correlation with mileage. As suggested in "B" that people took extra safety precautions and even cars were equipped with more advanced safety measures. Hence assuming though there were accidents fatalities were less because of the safety measures. Hence "B" resolves the paradox.

_________________

Aryama Dutta Saikia
Jamboree Education Pvt. Ltd.

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Guilio · Answer

Hi Karishma,

I still understand why this must be the case. The argument claims there was a drop in the number of car-crash fatalities  per highway mile driven by cars . If you the average mileage driven per car increased, which is like increasing our denominator, then  the number of car-fatalities per highway mile dropped automatically .

I get that B is better, but I still can't find a reason to eliminate D.

Question also to my predecessor: how has this argument nothing to do with mileage, when it talks about "car-crasher  per highway mile ".

truongynhi · Answer

Hi MrSobe17,

I had the same question as you, but after reading the explanation by Karishma I realize some things. Here are my thoughts on it:

1. We put some math in here. Remember Work-Rate problems in Quant? The stem is talking about RATE, right? What I know about rate is that if the denominator increases, the numerator has to increase proportionally in order to maintain the same rate. Although we are not explicitly told that the rate of death-to-mile remains the same, it is reasonable to think that the rate will not change. For example, I tell you that my accuracy rate when doing Data Sufficiency problems is 80%. Yesterday I did only 10 DS questions, hence the number of questions I got right is 8. Now I told you that today I have done 50 DS problems, you notice that the denominator sharply increases, right? But do you think I got only 2 out of 50 questions correct? (Sounds like I am a DS geek?) Probably not, because the more problems I do, the more incorrect answers I give. My accuracy rate will not change significantly in 1 day unless something SPECIAL happens.

Now, back to our death-mile case, it is intuitive to believe that the more miles people drive, the more they are prone to accident. If you only drive occasionally (several times a year), your chance of involving in a car accident is definitely less than when you have to drive long distance every single day for work purpose. So here, people are driving longer distance, so the number of fatilities tends to increase. It makes sense to me.

2. Remember I said my accuracy rate for DS problems will not change overnight unless something SPECIAL happens? Like, I out of the sudden become smarter, or the problem set I solved this morning includes hint attached to every question. Here, in this CR question, option B offers the special thing. The death-mile rate will not change by itself, but if there are changes in some special relevant other factors like stricter regulations, smarter safer cars, or better roads, the rate may change. This makes sense to you?

KarishmaB · Answer

I have taken this question on my blog. See if it helps: https://anaprep.com/critical-reasoning- ... verbal-cr/

shasadou · Answer

I am still calling into question the reasoning behind answers B and D. As for D: the stem has already told us the fatality/mile rate dropped - so it is given, there ARE factors that either impact the numerator or denominator or both - D completes the picture/explains by saying that the denominator increased. Here we are sort of forced to make a slight assumption that the fatality number should have risen at most at a lower rate than the milage driven for the equation to hold true. BUT the stem clearly says the rate is down, it is guaranteed ---> so combined with answer D we get the full picture.

As for A: I can find a number of reasons to challenge B. Automakers are lying (as we see with many recent cases) to consumers as regards features of the cars - so wearing a seatbelt does not result into a saved life. I have a friend who luckily avoided a fatality although the airbag did not jump out as should have as per the car specifications. All the people who wear seatbelts can be driving old rusty cars where seatbelt does not hold. There are numerous ways to challenge the B. If we accept the B as the right answer then we should accept that we also are making an additional assumption to make the B true: that the seatbelts and airbags are really working.

alpham · Answer

Wow, this one is just giving it to you with the seatbeats and airbags. Easy pre think too. Almost had to think if it was a trick question... haha

OreoShake · Answer

Completely agree with you. For B to be true, it has to be assumed that seatbelts and aribags do work. I was under the impression that it is not right to assume anything out of what is stated in the answer choices in CR. Apparently it is not so... Also, seatbelts' utility is not obvious or general knowledge, such as water being transparent. Weird answer.

Nightfury14 · Answer

The faster a car is traveling, the less time the driver has to avoid a potential accident, and if a car does crash, higher speeds increase the risk of a fatality. Between 1995 and 2000, average highway speeds increased significantly in the United States, yet, over that time, there was a drop in the number of car-crash fatalities per highway mile driven by cars. 
Which of the following, if true about the United States between 1995 and 2000, most helps to explain why the fatality rate decreased in spite of the increase in average highway speeds?

(A) The average number of passengers per car on highways increased. 
 (B) There were increases in both the proportion of people who wore seat belts and the proportion of cars that were equipped with airbags as safety devices.  
(C) The increase in average highway speeds occurred as legal speed limits were raised on one highway after another. 
(D) The average mileage driven on highways per car increased. 
(E) In most locations on the highways, the density of vehicles on the highway did not decrease, although individual vehicles, on average, made their trips more quickly.

kzivrev · Answer

Im in the same basket as you are , again one of the dirt games of GMAC, they rule, when they like to make assumption more than necessary is ok but we, so it is on their mersy how they did set up the algoritam on the test day to give you a correct or wrong answer consequently your score and you destiny depends on them. I did another question with weird reasoning. this is the question: an-influential-stock-analyst-recommends-the-purchase-224662.html go ahead and dismiss A. GMAC asume that workers were working and reading at the same time ??????????????????????????? GMAC can assume but can we like in the question above, D is more relaible and clean answer without any assumptions, just clean formula to consider and there you go. but no this time GMAC likes assumption not warranted in the paragraph??????????? go figure out what they want

KarishmaB · Answer

You don't need to "assume" that seatbelts and airbags work! They do! Note that option (B) clearly says "people who  wore  seat belts". So more people have started wearing seat belts. If a car has air bags, they will get deployed on their own so they are not dependent on people using them. They both add to the safety of the car. 
They might malfunction in some rare cases but mostly they work. 
If I say, "I bought him a new laptop," isn't it implied that he can use the laptop when he wants. Would I say I am assuming too much? That I should consider that the laptop may not work?

The faster a car is traveling, the less time the driver

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The faster a car is traveling, the less time the driver

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