When designing either the intersection of a driveway entrance with a road or the intersection of two roads, consideration should be given to the sight lines at both sides of the intersections.
A clear sight triangle is the proposed area within which the view of a driver in a typical vehicle at a driveway or road intersection is not to be obstructed in either driveway while stopped in the driveway or road.
How It Is Different From a Clear Sight Distance
A clear sight triangle can be confused with a clear sight distance. Both are similar in that they refer to sight lines that show how far a driver can see. However, they differ in how far back they start in the driveway or road and how the sight lines are defined.
The sight lines of a clear sight triangle can start as much as 75 feet back from the edge of paving of the intersecting road and are defined by required dimensions that are provided by local regulations. A clear sight triangle that starts back at 75 feet will probably be required to have the sides of the triangle extend to 75 feet on both sides of the intersection. The site contractor would have to be sure that there is nothing within this triangle area that would obstruct the view of a driver. This could mean removing vegetation or relocating certain things such as signs.
The sight lines of a clear sight distance might start at only 10 feet back from the edge of paving of the intersecting road and are defined by how far a driver in a vehicle would be able to see traffic driving toward the intersection in either direction. Also, measured clear sight distances are compared to required sight distances that are calculated. A proposed land development plan might have to call for the removal of vegetation, the relocation of things such as signs, or the shifting of the proposed driveway or road if measured sight distances are not equal to or greater than required sight distances.
How a Clear Sight Triangle Is Shown on a Plan
A clear sight triangle on a plan would obviously be shown as a triangle at a driveway or road intersection. The actual shape of the triangle will vary depending on the shape of the driveway and the intersecting road. The size of the triangle will vary depending on the required dimensions provided by local regulations.
There would also probably be a note on the plan describing the purpose of the triangle and what has to be done to create and maintain the triangle.
Where to Find Clear Sight Triangle Requirements
Clear sight triangle requirements can usually be found in one of the ordinances of the municipality within which a project is located. The applicable section of the ordinance should include the required size of the triangle and information regarding how to properly show the triangle on proposed land development plans.
Related: Land Development Regulations (A Simple Guide)
Why a Clear Sight Triangle Is Important
Having the required clear sight triangle prepared as a part of a land development plan and created during construction provides an extra level of safety for drivers who would want the extra room while driving to the edge of the intersection to start preparing for the next turn.