The use of radar detectors in commercial vehicles was banned because

IMO C

option C provides with a reasoning of the effect of ban of radar detectors on commercial vehicles , so the same effect would come on to non commercial vehicles as well & lower speed means increased safety ...

The use of radar detectors in commercial vehicles was banned because commercial truck and bus drivers were using these devices to drive faster than the posted speed limit without fear of arrest. (So the radars aided in driving fast without fear of arrest And banning them must decreased chances of going faster than speed limit)

Since drivers of noncommercial vehicles also use radar detectors and since speeding decreases safety for any vehicle, use of radar detectors should also be banned in noncommercial vehicles to increase safety. (author is suggesting that banning radars in noncommercial vehicles can improve safety and this improvement in safety can be attributed to the noncommercial vehicles observing speed limit)

A. The average noncommercial-vehicle driver is involved in less long-distance driving than is the average commercial-vehicle driver. (Wrong - Distance is not a factor in safety)

B. In many places airplanes or helicopters are used rather than radar to locate vehicles traveling faster than the posted speed limit. (Wrong - Helicopters and airplanes are out of scope for this argument)

C. The ban on radar detectors in commercial vehicles has been effective in deterring them from speeding. (Correct - if the ban was not effective in commercial vehicles, its unlikely to be effective in noncommercial vehicles. So for the ban in noncommercial vehicles to work, it must have been effective in commercial vehicles first)

D. Traffic accidents involving a truck or bus generally pose a greater threat of injury or death than do other accidents. (Wrong - Traffic accidents are out of scope)

E. Radar detectors are sometimes set off by devices other than the law enforcement devices that the radar detectors were built to detect. (Wrong - Other devices arre out of scope)
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Why is C correct? Isn't it implying a causal relationship, by saying that because the method works favourably for commercial vehicles, it should work for non commercial vehicles? As far as I know, this is one of the trap answers by the GMAT.

I would go with E, since it applies to both commercial & non commercial vehicles, and encourages overall safety of vehicles in general.

Could you please tell me if I'm going wrong here?

The use of radar detectors in commercial vehicles was banned because commercial truck and bus drivers were using these devices to drive faster than the posted speed limit without fear of arrest. Since drivers of noncommercial vehicles also use radar detectors and since speeding decreases safety for any vehicle, use of radar detectors should also be banned in noncommercial vehicles to increase safety.

Conclusion : use of radar detectors should also be banned in noncommercial vehicles to increase safety.
premise for the conclusion : speeding decreases safety for any vehicle

underlying assumption : non-commercial vehicles use radar detectors to drive faster than the speed limit

we need to strengthen the underlying assumption:

A. The average noncommercial-vehicle driver is involved in less long-distance driving than is the average commercial-vehicle driver.

the distances covered are out of scope as our argument depends on the issue of speeding.-wrong!

B. In many places airplanes or helicopters are used rather than radar to locate vehicles traveling faster than the posted speed limit.

we can use ANY method! however this doesn't prove the fact that radars should be banned for non-commercial vehicles!-wrong!

C. The ban on radar detectors in commercial vehicles has been effective in deterring them from speeding.
even though this option is not in line with the reasoning... this option proves that banning did have its intended effect therefore the ban will probably have a positive effect on non-commercial vehicles as well!!- Correct

D. Traffic accidents involving a truck or bus generally pose a greater threat of injury or death than do other accidents.
We are talking about banning radar detectors in non-commercial vehicles, we don't even know if a truck and a bus fall under commercial or non-commercial and even if they fall in any of these categories we do not know whether banning radar detectors will make it safer!---this option just does nothing- wrong!


E. Radar detectors are sometimes set off by devices other than the law enforcement devices that the radar detectors were built to detect.
these radar detectors are so advanced that vehicles using these detectors have even better chances of speeding and not getting caught --- however, this option doesn't prove how banning radar detectors in non-commercial vehicles will be useful i.e will make it safe!!
we need to prove that banning works

also we do not know whether the commercial and non-commercial vehicles are even using these radars--- we just know that such radars exist!- wrong!

Option C is the correct option!
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Why is C correct? Isn't it implying a causal relationship, by saying that because the method works favourably for commercial vehicles, it should work for non commercial vehicles? As far as I know, this is one of the trap answers by the GMAT.

this is pretty much the reason why the answer is correct! --- if we negate option C it weakens the argument--- if banning didn't work for commerical vehicles then maybe they should use a different method to make non-commercial vehicles safer! if banning is a bad idea it destroys the whole argument- the argument is assuming that banning is an awesome idea!

I would go with E, since it applies to both commercial & non commercial vehicles, and encourages overall safety of vehicles in general.

option E just proves that there are different kind of radars either way which ever radar it is--- they are all unsafe and they are used for the wrong reasons---- how is this strengthening the argument?


also we do not have any proof that the vehicles are using these radars-- the option just talks about the existence of these radars

i hope this helps
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