NC DOT 10 X 70 Sight Triangle

In the realm of transportation engineering, one crucial aspect that ensures safety and efficiency is the concept of sight distance triangles. These triangles serve as a critical tool for determining the maximum sight distance required for drivers to safely navigate intersections, avoiding potential hazards or accidents. Specifically, the NCDOT 10 x 70 sight triangle refers to a specific set of measurements and guidelines set forth by the North Carolina Department of Transportation. By establishing a defined area between a point 70 linear feet from the intersection edge, and another point situated ten feet from the opposing street right-of-way edge, this concept aims to provide optimal visibility for drivers approaching the intersection. Understanding and adhering to these sight distance requirements isn’t only essential for engineers and planners but also paramount for ensuring the safety and well-being of motorists traversing North Carolina's roadways.

What Is a Sight Triangle Used For?

A sight triangle, also known as a sight distance triangle, is essentially a designated area at the corners of road intersections and driveways. It’s purpose is to ensure that the view of approaching traffic remains unobstructed for drivers. This safety measure is crucial in preventing accidents and promoting efficient traffic flow.

The importance of sight triangles lies in their ability to provide adequate visibility for drivers, allowing them to make well-informed decisions when navigating intersections. By designating specific areas where views shouldn’t be obstructed, drivers can have a clear line of sight to oncoming traffic, pedestrians, and other road users.

How Is a Sight Triangle Calculated?

A sight triangle is calculated by considering three important factors: the distance for clear visibility, the height of obstacles, and the driver’s line of sight. The goal is to ensure that drivers have an unobstructed view of approaching vehicles or pedestrians. To calculate the sight triangle, specific formulas and guidelines are used, taking into account the speed limit, road type, and other variables. By determining the necessary sight distance, evaluating potential obstructions, and adjusting for different factors, engineers can design roads to maximize safety and minimize collision risks.

Line of sight intersection is a crucial concept in ensuring safe driving conditions. It refers to the minimum distance required for drivers entering a highway to have an unobstructed view of oncoming vehicles from both the right and left sides. Equally vital is the visibility of the entering driver to traffic approaching on the highway. This intersection sight distance is essential for preventing accidents and facilitating the smooth flow of traffic at junctions.

What Is the Line of Sight Intersection?

The line of sight intersection, commonly known as intersection sight distance, refers to the minimum length of unobstructed line of sight between a driver who’s entering a highway and the vehicles approaching from both the right and left on that particular highway. This concept is of utmost importance as it ensures that drivers entering the highway have a clear view of the traffic coming from both directions, enabling them to make safe decisions. Additionally, it also ensures that the drivers entering the highway are visible to the oncoming traffic, further enhancing safety at intersections.

To ensure the line of sight intersection meets the required standards, it’s crucial for transportation authorities, such as the North Carolina Department of Transportation (NC DOT), to enforce guidelines and regulations. One such example is the NC DOT 10 X 70 Sight Triangle, which specifies the minimum sight distance requirements for various types of intersections. This sight triangle ensures that drivers have an adequate line of sight by requiring a clear zone of 10 feet wide and 70 feet long on both the major and minor roadways. Compliance with these regulations helps create safe and efficient transportation networks.

Furthermore, proper line of sight intersection design should consider factors such as road geometry, the presence of vegetation or obstacles, and traffic conditions. Removing or trimming obstructive vegetation, ensuring clear signage, and implementing appropriate road markings are some measures that can contribute to an improved line of sight intersection. Regular maintenance and inspection of these intersections are also necessary to promptly address any visibility issues that may arise.


By delineating an area between two specific points on opposite street right-of-ways, this design principle enables drivers to have sufficient visibility and reaction time, ultimately reducing the risk of accidents. The implementation of sight distance triangles not only complies with NCDOT standards but also enhances the overall traffic safety infrastructure. With Figured 5.1.7. B as a visual reference, it’s evident that this geometric concept is an essential consideration for engineers and planners when designing roadways in North Carolina. By prioritizing clear sight lines and implementing these guidelines, the NCDOT is actively working towards creating a safer transportation network for all road users.

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