6A. Intersection sight distance

Question 1

Where can information about Intersection sight distances be found?

Answer 1

AASHTO chapter 9.5

Question 2

What are the four subsections of intersection sight distances

Answer 2

1. General Considerations
2. Sight Triangles
3. Intersection Control
4. Effect of Skew

Question 3

What is the standard height of an object seen by a driver when calculating intersection sight distances

Answer 3

As in the case of passing sight distance, the object to be seen by the driver in an intersection sight distance situation is another vehicle. Therefore, design for intersection sight distance is based on the same object height used in design for passing sight distance.

3.50 ft [1.08 m].

Question 4

What is the maximum height of an object in the “clear sight triangle”

Answer 4

Any landscaping in the clear-sight triangle should be low growing and should not be higher than 3 ft [1.0 m] above the level of the intersecting street pavements.

Question 5

What is a sight triangle?

Answer 5

Specified areas along intersection approach legs and across their included corners should be clear of obstructions that might block a driver’s view of potentially conflicting vehicles. These specified areas are known as clear sight triangles. The dimensions of the legs of the sight triangles depend on the design speeds of the intersecting roadways and the type of traffic control used at the intersection. These dimensions are based on observed driver behavior and are documented by space-time profiles and speed choices of drivers on intersection approaches (21).
Two types of clear sight triangles are considered in intersection design—approach sight triangles and departure sight triangles.