Question

Motorists in a certain country frequently complain that traffic congestion is much worse now than it was 20 years ago. No real measure of how much traffic congestion there was 20 years ago exists, but the motorists' complaints are almost certainly unwarranted. The country's highway capacity has tripled in the last twenty years, thanks to a vigorous highway construction program, whereas the number of automobiles registered in the country has increased by only 75 percent.
Which of the following, if true, most seriously weakens the argument?

• A. Most automobile travel is local, and the networks of roads and streets in the country's settled areas have changed little over the last 20 years.
• B. Gasoline prices are high, and miles traveled per car per year have not changed much over the last 20 years.
• C. The country's urban centers have well-developed public transit systems that carry most of the people who commute into those centers.
• D. The average age of automobiles registered in the country is lower now than it was 20 years ago.
• E. Radio stations have long been broadcasting regular traffic reports that inform motorists about traffic congestion.

Hint:

In critical reasoning, always be skeptical of arguments that use broad, aggregate statistics (like national highway capacity) to draw conclusions about specific, local experiences (like a daily commute). The correct weakening answer often points out this discrepancy.

Answer 1

The Correct Option is A

Step 1: Understanding the Argument
The argument aims to disprove motorists' complaints about increased traffic congestion.
Conclusion: The motorists' complaints are unwarranted.
Evidence: Over the last 20 years, national highway capacity has tripled (increased by 200%), while the number of registered automobiles has only increased by 75%.
Assumption: The argument assumes that the national statistics for highway capacity are a relevant measure of the traffic conditions experienced by the average motorist. It equates "highway capacity" with the capacity of the roads people actually use for their daily travel.

Step 2: Analyzing the Task
We need to find an option that weakens the argument's conclusion. This means we must find a reason why the motorists' complaints might be valid, despite the statistics presented. The best way to do this is to attack the argument's central assumption.

Step 3: Evaluating the Options
(A) This option directly attacks the core assumption. If most travel is local, and the local road networks have not been significantly upgraded, then the massive expansion of national highways is irrelevant to the daily experience of congestion on local streets. It's entirely possible for national highway capacity to triple (e.g., by building new inter-city freeways) while city streets become much more congested due to the 75% increase in cars crowding onto an unchanged local road system. This explains why motorists would perceive congestion as worse, thereby weakening the argument.
(B) If miles traveled per car have not changed, it means the 75% increase in cars translates directly to a 75% increase in total miles traveled. This doesn't weaken the argument; it just clarifies the demand side. The argument's logic still rests on capacity (tripled) far outpacing this demand.
(C) Well-developed public transit would reduce the number of cars on the road, which would alleviate traffic congestion. This would strengthen the author's argument that the complaints are unwarranted, not weaken it.
(D) The average age of automobiles has no bearing on the amount of traffic or congestion on the roads.
(E) The existence of traffic reports simply confirms that congestion is a known issue. It does not provide any information to weaken the argument's specific claim that congestion is not worse than it was 20 years ago.
Step 4: Final Answer
Option (A) is the correct answer because it exposes a flaw in the argument's reasoning by highlighting the potential mismatch between the evidence (national highway capacity) and the phenomenon being discussed (local traffic congestion).