If a horizontal curve on a two-lane road were to turn left, what would be true about the lanes?

In the context of a left turn on a horizontal curve for a two-lane road, the geometry of roadway design becomes essential for safety and vehicle dynamics. When a vehicle is navigating a left curve, the lanes are designed to accommodate the forces acting on the vehicle, particularly due to centrifugal force.

When the road curves to the left, the outside lane (the lane on the left side of the curve) must slope downward to manage the lateral forces acting on vehicles. This inward pitch helps to counteract the centrifugal force that pushes vehicles outward, thus reducing the risk of skidding or losing control.

Conversely, the inside lane (the lane on the right) also needs to slope but typically does so to a lesser degree. However, saying that both lanes slope down to the left is accurate because, generally, both the inside and outside lanes will be designed with a slight left slope to help maintain proper drainage and vehicle stability. This design ensures that water does not accumulate on the driving surface and improves overall safety.

Therefore, sloping both lanes down to the left provides additional banking, allowing for a more stable and secure driving experience for vehicles turning left on a curve.