On what basis are Friction Courses required according to AADT and Design Speed?

Friction courses are designed to enhance the skid resistance of asphalt surfaces, particularly in circumstances where traffic volume and speeds indicate a need for increased safety. The requirement for friction courses is based on the annual average daily traffic (AADT) and the design speed of the roadway.

In this case, the correct choice identifies the minimum threshold where AADT exceeds 3000 vehicles per day and the design speed is above 35 mph. This combination suggests a sufficient volume of traffic coupled with higher speeds, indicating a potential for higher risk of skidding incidents. The friction course helps to mitigate this risk by improving the surface characteristics of the pavement, allowing for better tire contact and grip, which is crucial for safety in these scenarios.

Given these factors, this option establishes a practical baseline for applying friction courses based on how they relate to traffic conditions and vehicle dynamics on the road, ultimately aiming to enhance overall roadway safety.