In road safety and driving, collisions often occur on curves primarily because which speed-related condition is true?

Introduction / Context:
Curves and bends in roads are locations where many accidents occur. Understanding why speed is a critical factor on curves is important for both driving exams and general safety awareness. This question asks you to identify the main speed-related reason collisions occur at curves.

Given Data / Assumptions:
- The focus is on collisions at curves and how they relate to vehicle speed.
- Options distinguish between high approach speed, low approach speed, and issues when leaving the curve.
- We assume standard principles of vehicle dynamics and road safety.

Concept / Approach:
When a vehicle enters a curve, it experiences centripetal force that depends on its speed and the radius of the curve. If the approach speed is too high for the sharpness of the curve and the road conditions, the tires may lose grip, causing the vehicle to skid, slide outward, or cross into another lane. Properly slowing down before entering the curve is therefore critical. Exiting speed also matters, but most loss-of-control events begin at the point of entry when the driver fails to slow sufficiently.

Step-by-Step Solution:
Step 1: Recognize that curves require lower speed than straight sections because of increased lateral forces on the vehicle. Step 2: Recall that drivers are advised to “slow down before the curve” rather than braking hard while turning. Step 3: Understand that if a driver enters a curve too fast, the vehicle may drift outward, cross lanes, or leave the roadway. Step 4: Compare the options and identify the one that describes excessive speed on the approach to the curve. Step 5: Select that option as the main reason collisions occur at curves.

Verification / Alternative check:
Road safety manuals and driving test guides consistently emphasize slowing before entering curves. Warning signs and advisory speed limits are often posted before sharp bends, not after them, confirming that approach speed is a major concern. Accident statistics also show many run-off-road crashes at the initial part of curves.

Why Other Options Are Wrong:
Option B: Too little speed when leaving a curve does not typically cause collisions; lower speed is generally safer.
Option C: This suggests approach speed is always safe, which contradicts real-world evidence that entering too fast is dangerous.
Option D: Very low speed on the approach may annoy other drivers but will not usually cause skidding; skids are more commonly associated with excessive speed or poor traction.

Common Pitfalls:
Drivers sometimes misjudge how sharp a curve is or how much grip the road has, especially in wet or icy conditions, and fail to reduce speed sufficiently. Another pitfall is braking hard in the middle of the curve instead of slowing beforehand, which can upset the vehicle's balance and increase the risk of loss of control.

Final Answer:
The correct answer is speed on the approach to the curve is too great to maintain control because entering a curve too fast is a primary cause of collisions at bends in the road.