Excludability Enables Congestion Pricing

Steps:

• Congestion occurs when roads are rivalrous, as one vehicle's use reduces availability for others.
• Charging fees aims to reduce usage by making access costly.
• For fees to work, non-payers must be excluded from using the roads.
• Thus, excludability is essential to enforce pricing and curb overuse.

Why A is correct:

• Excludability means access can be restricted to payers, allowing the government to implement tolls that price out excess users and alleviate congestion, per public economics principles.

Why the others are wrong:

• B: Rivalrous goods experience congestion, but this describes the problem, not the condition for successful charging.
• C: Non-rivalrous goods allow unlimited use without interference, so charging wouldn't reduce congestion.
• D: Public goods are non-excludable, preventing effective fees as free-riders can't be stopped.

Final answer: A