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Difficulty: HardWeakening Arguments

To mitigate severe summer train delays caused by the thermal expansion of steel tracks, a municipal transit authority plans to coat all exposed rail lines with a solar-reflective ceramic finish. In pilot testing conducted on an unused, stationary track segment, the coating reduced peak surface temperatures by 15°C, keeping the metal well below the critical temperature at which heat-induced warping occurs. The authority concludes that implementing this coating systemwide will successfully eliminate heat-related train slowdowns. Which of the following, if true, most seriously undermines the transit authority's conclusion?

  1. A
    Recent chemical enhancements to ceramic coatings have significantly reduced their purchasing cost while increasing overall solar heat reflectivity.
  2. B
    Air conditioning system failures on older passenger cars account for a larger proportion of passenger delay complaints during summer months than track warping does.
  3. The intense friction generated by the steel wheels of active, heavy train traffic rapidly abrades the ceramic coating, stripping it off the rails within days of operational use.Answer
  4. D
    The thermal expansion threshold of steel rails manufactured within the last five years is slightly higher than that of older steel rails currently in service.
  5. E
    Applying the ceramic coating requires maintenance crews to conduct track work during nighttime hours when ambient temperatures are lowest.

Answer

The argument is most seriously weakened by the fact that the friction of active train traffic rapidly abrades and strips the ceramic coating off the rails within days.
The correct answer undermines a key assumption of the plan: that the ceramic coating will remain effective under real-world operating conditions as it did on an unused test track. By showing that mechanical friction from heavy train traffic rapidly strips the coating off the rails, this choice demonstrates that the plan cannot achieve its goal of preventing summer track warping.

Step-by-Step Solution

1
Deconstruct the argument core
Premise: In a pilot test on an unused, stationary track, solar-reflective ceramic coating lowered peak metal surface temperatures by 15°C, preventing thermal warping. Conclusion: Systemwide application on operational tracks will eliminate heat-related slowdowns.
Identifying the author's logical leap from a stationary test environment to real-world operating conditions reveals the underlying assumption.
2
Identify the unstated assumption
The author assumes that conditions on active, heavily trafficked rail lines will not interfere with the coating's durability or thermal performance compared to the stationary test line.
Plan-to-goal arguments rely on the implicit premise that pilot conditions accurately forecast operational realities.
3
Evaluate the impact of new evidence
If high-frequency heavy train traffic removes the coating almost immediately through wheel friction, the coating cannot maintain its reflective benefits, completely undermining the plan's expected outcome.
Showing that real-world operational factors negate the key mechanism demonstrated in the pilot directly breaks the link between the premise and conclusion.

Key Concept

Extrapolation from Pilot Conditions to Operational Environments
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Topics

Weakening Arguments

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