How many types of sight distances are recognized in roadway design?

• A. 2
• B. 3
• C. 4
• D. 5

Answer: (C)

In roadway design, four main types of sight distances are recognized: stopping sight distance, passing sight distance, decision sight distance, and necessary sight distance. Each type serves a specific purpose in ensuring safe and efficient transportation.

Stopping sight distance is the minimum distance required for a driver to see an obstacle and come to a complete stop without colliding with it. This distance is crucial for safety, particularly on curves and at intersections.

Passing sight distance is important for overtaking slower vehicles safely. It measures the distance required for a driver to complete a pass maneuver, considering factors like vehicle speed and acceleration, ensuring that there is enough visibility and roadway length for a vehicle to safely overtake.

Decision sight distance provides drivers with the necessary reaction time to recognize a decision point, such as an intersection or a change in road conditions. This distance allows for safe maneuvering when making navigational decisions.

Necessary sight distance is the total distance a driver must see ahead to react appropriately to any potential hazards on the road.

Recognizing these four distinct types of sight distances is essential for engineers and planners to design roadways that promote safety and efficiency for all users.