Critical Reasoning

The city's transportation department has noticed that the city's extensive public bus system generally runs behind schedule on days when traffic is heavier in the city. The transportation commissioner concluded that the traffic prevents the buses from reaching their stops on time, despite the existence of a number of bus-only lanes throughout the city. He has therefore proposed creating additional bus-only lanes on city streets to allow more buses to bypass traffic.

The success of the commissioner's proposal depends on which of the following assumptions?

A)Similar proposals have been effectively implemented in other cities.

B)The city's bus-only lanes do not contribute substantially to gridlock by reducing the number of lanes available to other traffic.

C)An increase in bus fare is not necessary as a result of the proposal.

D)The city owns enough buses to cover all established routes.

E)Automobile drivers will not object to the proposal.

OA B

Can anyone explain me how OA is correct??

Conclusion : additional bus-only lanes on city streets to allow more buses to bypass traffic.

If the assumption is like this: The city's bus-only lanes do contribute substantially to gridlock by reducing the number of lanes available to other traffic. Then will also Conclusion remain true and same.

If the assumption is like this: The city's bus-only lanes do not contribute substantially to gridlock by reducing the number of lanes available to other traffic.Then will also Conclusion remain true and same.

So please explain me how can OA is correct??

Soumita Ghosh wrote:The city's transportation department has noticed that the city's extensive public bus system generally runs behind schedule on days when traffic is heavier in the city. The transportation commissioner concluded that the traffic prevents the buses from reaching their stops on time, despite the existence of a number of bus-only lanes throughout the city. He has therefore proposed creating additional bus-only lanes on city streets to allow more buses to bypass traffic.

The success of the commissioner's proposal depends on which of the following assumptions?

A)Similar proposals have been effectively implemented in other cities.

B)The city's bus-only lanes do not contribute substantially to gridlock by reducing the number of lanes available to other traffic.

C)An increase in bus fare is not necessary as a result of the proposal.

D)The city owns enough buses to cover all established routes.

E)Automobile drivers will not object to the proposal.

This a PLANNING argument.
The plan links CREATING ADDITIONAL BUS-ONLY LANES to HELPING BUSES REACH THEIR STOPS ON TIME.
The assumption is WHAT MUST BE TRUE for the plan to work.
Answer choice B, negated: The city's bus-only lanes CONTRIBUTE SUBSTANTIALLY TO GRIDLOCK by reducing the number of lanes available to other traffic.
If the bus-only lanes cause gridlock, then the argument cannot conclude that CREATING ADDITIONAL BUS-ONLY LANES will help buses REACH THEIR STOPS ON TIME.
Since the negation of B invalidates the conclusion, B is the necessary assumption: WHAT MUST BE TRUE for the plan to work.

The correct answer is B.

Conclusion : additional bus-only lanes on city streets to allow more buses to bypass traffic.

If the assumption is like this: The city's bus-only lanes do contribute substantially to gridlock by reducing the number of lanes available to other traffic. Then will also Conclusion remain true and same.

Hi Soumita,

You are on the right track and did negate it correctly - The city's bus-only lanes contribute substantially to gridlock by reducing the number of lanes available to other traffic.
Now if the bus only lanes are contributing substantially to gridlock, is it a good idea to increase the lanes??? This is hitting the conclusion.

The conclusion here is - creation of additional lanes.

See how negating the argument made the conclusion fall apart.
Do you get it now??

GMATGuruNY wrote:

Soumita Ghosh wrote:The city's transportation department has noticed that the city's extensive public bus system generally runs behind schedule on days when traffic is heavier in the city. The transportation commissioner concluded that the traffic prevents the buses from reaching their stops on time, despite the existence of a number of bus-only lanes throughout the city. He has therefore proposed creating additional bus-only lanes on city streets to allow more buses to bypass traffic.

The success of the commissioner's proposal depends on which of the following assumptions?

A)Similar proposals have been effectively implemented in other cities.

B)The city's bus-only lanes do not contribute substantially to gridlock by reducing the number of lanes available to other traffic.

C)An increase in bus fare is not necessary as a result of the proposal.

D)The city owns enough buses to cover all established routes.

E)Automobile drivers will not object to the proposal.

This a PLANNING argument.
The plan links CREATING ADDITIONAL BUS-ONLY LANES to HELPING BUSES REACH THEIR STOPS ON TIME.
The assumption is WHAT MUST BE TRUE for the plan to work.
Answer choice B, negated: The city's bus-only lanes CONTRIBUTE SUBSTANTIALLY TO GRIDLOCK by reducing the number of lanes available to other traffic.
If the bus-only lanes cause gridlock, then the argument cannot conclude that CREATING ADDITIONAL BUS-ONLY LANES will help buses REACH THEIR STOPS ON TIME.
Since the negation of B invalidates the conclusion, B is the necessary assumption: WHAT MUST BE TRUE for the plan to work.

The correct answer is B.

Hi Mitch,

By negating the choice to find the assumption, it must weaken the argument. However, (B) seems to strengthen the argument because "The city's bus-only lanes CONTRIBUTE SUBSTANTIALLY TO GRIDLOCK by reducing the number of lanes available to other traffic."

in other words, the city's traffic is better if increasing the number of lanes. Consequently, if we negate the argument, it seems to strengthen the argument.

Can you please clarify my points? Million thanks in advance.