Which data element is necessary to determine whether a roadway is nominally safe?

• A. The rate of superelevation for a high-speed horizontal curve along the roadway
• B. Average vehicle speed on the road
• C. Number of traffic signals
• D. Pavement texture

Answer: (A)

On a high-speed horizontal curve, the road is banked through superelevation to balance the outward centrifugal force that riders experience at design speeds. The rate of superelevation directly shows whether the curve’s geometry is designed to keep vehicles stable and maintain control through the bend. If the banking is appropriate for the expected speeds, the lateral forces are managed and skidding or rollover risk is reduced, making the roadway safer in a nominal sense.

Other data elements influence safety in other ways, but they don’t directly indicate whether the curve’s geometry is safely designed for those speeds. Average vehicle speed tells you how fast drivers are going, not whether the curve is banked correctly. The number of traffic signals relates to control at intersections, not the curve’s safety design. Pavement texture affects friction, but even with good texture, inadequate superelevation can compromise curve safety.