Which statement describes traction correctly?

• A. Traction is always constant
• B. Traction decreases as speed increases
• C. Traction is unaffected by road texture
• D. There is only ever a limited amount available

Answer: (D)

Traction is the grip between the tires and the road, created by friction at the tire–road interface. For any given set of conditions there is a maximum amount of friction available, so there is only a limited amount of traction you can rely on. This maximum is roughly μN, where μ is how sticky the surface and tire are (affected by road texture, moisture, ice, wear, etc.) and N is the weight on the tires.

That means traction can change with conditions: dry pavement usually provides more grip than wet or icy surfaces; worn tires or proper tire pressure can reduce the available grip; road texture and surface condition also influence how much grip you can get. When you demand more friction than what the surface can supply—like braking hard or accelerating quickly—the tires can slip, indicating you’ve reached that limit.

So the statement that there is only ever a limited amount of traction available best captures the reality of how grip works in driving.