The Correct Answer and Explanation is:
The correct answer is C. speed on the approach is too great.
Most collisions on curves happen because drivers fail to reduce their speed adequately before entering the turn. The physics of vehicle motion dictates this outcome. When a car travels in a straight line, its inertia wants to keep it moving in that same straight line. To navigate a curve, a force, known as centripetal force, must act on the car to pull it towards the center of the turn. This essential force is generated by the friction between the vehicle’s tires and the road surface.
The amount of centripetal force required to keep a car on a curved path increases exponentially with speed. Specifically, it is proportional to the square of the vehicle’s velocity. This means that even a small increase in speed requires a much larger amount of friction to hold the car in the turn. Every road surface and tire combination has a maximum limit of friction it can provide.
If a driver approaches a curve at a speed that is too great, the required centripetal force can exceed the maximum available friction. When this happens, the tires lose their grip on the road. The car’s inertia takes over, and it begins to slide in a direction tangential to the curve, often leading to it leaving its lane, running off the road, or colliding with an obstacle or oncoming traffic.
Option A is incorrect because insufficient speed is a safety measure, not a cause of collisions on curves. Option B is also incorrect because while accelerating too aggressively when leaving a curve can cause a loss of traction, the primary and most common error is entering the curve with excessive speed in the first place. The critical decision and action, slowing down, must happen on the straightaway approach before the turn begins.
