- Drivers must have a clear view of an entire intersection so they can see traffic control devices and see far enough upstream or downstream along an intersecting road to identify acceptable gaps in cross traffic before pulling onto the intersecting road. All quadrants of an intersection must have a triangular area (i.e., sight triangle) free of obstructions that could potentially obstruct the driver’s view of conflicting vehicles or users.
- The sight triangles used to determine intersection sight distance are (1) approach sight triangles and (2) departure sight triangles. Approach sight triangles
- Table 5.3 lists portions of the Green Book that address intersection sight distance.
| Table 5.3 Green Book References for Selecting Intersection Sight Distance | ||||
|---|---|---|---|---|
| Case | Intersection Type and/or Maneuver | Sight Triangle | Sight Distance Determinant | Green Book References |
| A | Intersection with no control | Approach triangle | SSD with modified assumptions | Exhibit 9-51 p. 655 |
| B | Intersections with stop control on the minor road | |||
| B1 | Left turn from minor road | Departure triangle | Gap time equation | Exhibit 9-54 p. 659 |
| B2 | Right turn from minor road | Departure triangle | Gap time equation | Exhibit 9-58 p. 664 |
| B3 | Crossing maneuver from minor road | Departure triangle | Gap time equation | Exhibit 9-58 p. 664 |
| C | Intersections with yield control on the minor road | |||
| C1 | Crossing maneuver from minor road | Approach triangle | SSD with modified assumptions | Exhibit 9-60 p. 667 |
| C2 | Left turn from minor road | Departure triangle | Gap time equation | Exhibit 9-64 p. 672 |
| D | Intersections with traffic signal control | Both | See Case D Guideline | p. 671 |
| E | Intersections with all-way stop control | None | None required | p. 674 |
| F | Left turns from major road | Departure triangle | Gap time equation | Exhibit 9-67 p. 675 |
SSD = Stopping Sight Distance
CONTACT:
Chris VanDyke
Research Scientist | Program Manager
chrisvandyke@uky.edu
