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A. Purpose. The purpose of this section is to ensure adequate sight distance for all users at intersections.

B. Sight Distance Triangle. The sight distance triangle is described by two intersecting lines of a specified length (a) and (b) which correspond to the straight line projections of the pavement edges or curb face and a third line which connects the extremities of the other two, as shown in the table and Figure 21.52.040A below. The location of the pavement edge or curb face shall be for a fully developed street that meets City standards for the classification.

Table 21.52.040
Required Horizontal Sight Clearance

Type of Intersection

Horizontal Sight Clearance for Intersection Legs Noted

(A)

(B)

Controlled by Traffic Signal or Stop Sign

Intersections that Involve Arterials (30MPH+)

20 feet

100 feet

Others (Local access, driveways, etc.) (25 MPH)

20 feet

65 feet

Uncontrolled or Yield on Public Local Access Street

70 feet

70 feet

Figure 21.52.040A
Sight Distance Triangle

Sight distance triangle

C. Obstructions Prohibited. The obstruction of a motor vehicle operator’s view at an intersection shall be prohibited within the “Sight Distance Triangle” described in this section and in RZC Appendix 2, Construction Specification and Design Standards for Streets and Access, between a height of two feet and eight feet above existing street grade. The sight triangle shall be applied in both directions along major and minor intersecting streets. Sight triangles from streets into a driveway may not apply in circumstances where the Department of Public Works determines that on-site constraints prevent the application of the sight distance requirements and there is no detriment to the public safety and welfare, including pedestrian access and safety. In the Downtown, Overlake urban center, and Marymoor Subarea, when a garage access intersects a street, along the street direction, the sight distance triangle either 20 feet by 65 feet or 20 feet by 100 feet shall be required depending on the street classification; along the garage access direction, a sight distance triangle of 20 feet by 65 feet may be replaced by a pedestrian sight distance triangle. A pedestrian sight distance triangle is described by two 10-foot intersecting lines that are drawn respectively along the back of sidewalk edge and along the edge of a garage access, and a third line which connects the extremities of the two 10-foot intersection lines.

Fences, hedges, signs, shrubs, natural vegetation and trees, and other inanimate objects greater than 18 inches in width or diameter are not allowed in the sight distance triangle. Traffic control devices, utility poles, trees, and other opaque inanimate objects 18 inches or less in width or diameter are allowed in the sight distance triangle when spaced at an adequate distance to not significantly obstruct the sight distance triangle.

Figure 52.3
Obstructions Prohibited

D. Vertical Sight Distance at Intersections.

1. Minimum vertical sight distances shall be established by the Department of Public Works consistent with vehicular speeds and stopping sight distance.

2. These standards shall be published, placed in RZC Appendix 2, Construction Specification and Design Standards for Streets and Access, and be made available to the public.

E. Special Cases. Where unusual conditions, such as roundabouts, preclude the application of this section in a reasonable manner, the Department of Public Works may establish minimum sight distances based on the intent of this section. These minimum sight distances may be more restrictive than provided above. Minimum sight distances for roundabouts are provided in the City’s Roundabout Design Manual. (Ord. 2652; Ord. 3028)

Effective on: 2/27/2021