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Sight Distance Guidelines

Sight Distance At Intersections
  1. General: These guidelines establish the areas around all intersections and driveways, the sight distance triangle that must be kept clear of sight obstructions. The sight distance triangle depends primarily on the required visibility at the intersection or driveway. It is determined by the type of intersection control (stop sign, traffic signal or no control) and the speed limit on the major road or street entered upon. In the following subsections, the sight distance requirements used to properly establish sight distances triangles at various types of intersections and driveways are presented. Table 2 lists recommended (desirable) and minimum (required) sight distance values and Figures 1, 2, 3.a and 3.b show corresponding sight distance triangles.

  2. Types of Intersections and Driveways: Table 1 summarizes the characteristics of various types of intersections and driveways.

TABLE 1. Types of Intersections and Driveways.
Use this table to determine type (A through F)
All cases except driveways
Type Average Daily Traffic (ADT) on Major Street or Street Entered Upon. Control Type Speed Limit (MPH) on Major Street or Street Entered Upon.
A < 1000 None 25
B Any Stop sign Any
C1 < 1000 Yield (four legged intersection) 25
C2 < 1000 Yield (T intersection) 25
D Any Signal Any
F Cases not covered by Types A through D
Driveways (includes vehicular access easements and tracts)
Type

Driveway PM Peak Volume

Major Street Average Daily Traffic

E1 <10 <6000
E2 10 ≥ and < 50 Any
E3 50 ≥ and ≤ 200 Any
E4 > 200 Any
F Cases not covered by Types E1 through E4
  1. How to Establish Sight Distance Triangles: Sight distance triangles for various types of intersections and driveways are shown in Figures 1, 2, 3.a and 3.b. In these figures, the sight distance triangles are represented by the shaded areas. Point A, or driver's decision point, represents the location of the driver; Point B is located on the major road at a specific distance (to the right and to the left) from the driver. This distance, referred to as the required sight distance, represents how far (on the major road) the driver should be able to see so as to safely exit a minor road or driveway or to make a right turn on red at a signalized intersection. Table 2 shows (in the right most columns) the sight distances values that need to be used to determine the sight distance triangle at various types of intersections and driveways.

    For uncontrolled intersections (no traffic light, stop sign or yield sign described in Type A/Figure 1) or a yield controlled intersection described in Type C/Figure 3.a, contact Iris Cabrera, City Transportation Engineer, at (425) 587-3866 to have the Public Works Department determine the required site distance triangle.

TABLE 2. Sight Distance Triangle Guidelines
Type of Intersection/Driveways Distance from Edge of Traveled Way (ft) Major Street (Street Entered Upon)
Average Daily Traffic

Speed Limit (MPH)

Sight Distance Value (ft)a
(B-C1) and B-C2)

Recommended (Desirable) Minimum (Required)d
A-Uncontrolled
(See Figure 1)
115b <1000 25 115 115
B - Stop Control on Minor Street
(See Figure 2)
14 Any 25 280 150
30 335 200
35 390 250
C - Yield Sign on Minor Street
C-1: Four-Legged Intersection
(See Figure 3.a)
130c 25 295 295
30 355 355
35 415 415
C-2: T-Intersection
(See Figure 2)
80c 25 295 295
30 355 355
35 415 415
E1 - E4 Driveways (See Figure 2)
E1
(<10 PM Peak Trips)
10 <6000 25 150 150
30 200 200
E2
(10-49 PM Peak Trips)
14 <6000 25 150 150
30 200 200
35 250 250
>6000 25 280 150
30 335 200
35 390 250
E3
(50-200 PM Peak Trips
14 <6000 25 150 150
30 200 200
14 >6000 25 280 150
30 335 200
35 390 250
E4
(>200 PM Peak Trips)
14 <6000 25 280 150
30 335 200
14 >6000 25 280 150
30 335 200
35 390 250

Footnotes:
a These values should be adjusted for grades with slopes of a magnitude of grade greater than 3%, number of lanes greater than two, for skewed intersections or for design vehicles other than passenger cars, using the intersection sight distance procedures in Chapter 9 of a Policy on Geometric Design, AASHTO, 4th Edition.
b
Distance back from center of intersection.
c Distance back from point C1 or C2 for types C-1 and C-2 intersections.
d Minimum (Required) only permitted if Recommended (Desired) is not possible.

  1. The values in Table 2 referred to as Recommended (Desirable)sight distance are based on the intersection sight distance procedures in Chapter 9 of A Policy on Geometric Design, AASHTO, 4th Edition.

  2. The values on Table 2 referred to as Minimum (Required) sight distance are based on the stopping sight distance values in Chapter 3 of A Policy on Geometric Design, AASHTO, 4th Edition.

  3. The values on Table 2 on page 2, referred to as Minimum (Desirable) and Minimum (Required) above is important. Wherever reasonably feasible, the Recommended values should be used. This is typically the case in new construction. Only when the Recommended values cannot be reasonably achieved should the Minimum values be considered. It is important that every reasonable effort be used to make the Recommended sight distance available, but it is understood that in some cases the difficulty in doing so is unreasonably disproportionate to the benefits gained. If less than the Recommended, but more than the Minimum can be provided, the distance provided should be maximized.

  4. To determine the Average Daily Traffic for Intersections A, B, C, C-1, C-2 and D, see the Traffic Count Summary attached to the instructions ("Sight Distance Procedures" section).

  5. To determine the Average Daily Traffic for Driveways E1 through E4, use the PM Peak Trips Calculation Spreadsheet under the "Sight Distance Procedures" section. Using the spreadsheet, insert the size of the project and the formula will calculate the average daily trips for the use(s) on the subject property.

  1. Permissible Intrusion in the Area To Be Kept Clear of Site Obstruction

General - Except as stated in subsection (4)(b) of this section or unless specifically approved by the Public Works Director, no structure, improvement, vegetation or other objects may be within the area to be kept clear of site obstructions between three (3) feet and eight (8) feet above the elevations of the pavement edge of each intersecting street, private driveway, or vehicular access easement or tract where that street, driveway or vehicular access easement or tract meets the points of the triangle that form this area furthest away from the intersection.

Exceptions - The following are permitted to be within the area that must be clear of site obstructions: Natural and fabricated objects and natural topography of the ground if the Public Works Director determines that adequate visual access is available. However, to fulfill the intent of this section, the Public Works Director may require land surface modification as part of any development activity on the subject property.

  1. Description of Intersections Types A through F

Type A - Uncontrolled Intersections

Uncontrolled intersections are not controlled by either stop or yield signs. They are usually located on streets that carry very low volumes and have a 25 MPH speed limit. Figure 1 below shows the sight distance triangle for this type of intersection. In this Figure, Point A and each point B are located on the center of the intersecting street approaches, 115 ft from Point C, which is located in the center of the intersection. The sight distance triangle area that must be kept free of site obstructions is the shaded area limited by segments AC, BC, and AB.

Sight Distance Figure 1

Type B - Stop Controlled Intersections

Type B intersections are those at which the minor street approaches are controlled by stop signs. Sight distance triangle to the left is the shaded area bounded by segments A-B, B-c2 and A-C2; where as sight distance triangle to the right is the shaded area bounded by the A-B, B-C1 and A-C1 segments as shown in Figure 2 below. Point A, or decision point, is located in the center of the minor street approach lane, 14 ft. from the edge of the major road's traveled way. The traveled way is the portion of the road intended for the movement of vehicles and bicycles, exclusive of shoulders and turning lanes. Point B is located on the center of the through lane on the major street (or in the center of the major street approach if more than one lane exists), a specific distance left and right from Points C1 and C2. The distance C1-B (same as C2-B) is the required site distance, which can be found in Table 2.

Although it is not typical to do so, if a parking lane exists on the major street, it may be excluded from the traveled way in special cases. Usually these are cases where volumes and speeds are low and therefore the overall safety risk at the intersection is considered low.

Sight Distance Figure 2

Type C - Yield Controlled Intersections

Two sight distance triangles need to be considered for Yield-controlled intersections: approach and departure sight distance triangles. The approach sight distance triangle is the area that must be free of obstruction that may block an approaching vehicle's view of potentially conflicting vehicles. The departure sight distance triangle is the area that must be clear of obstructions that may block the view of a stopped vehicle. These sight distance triangles are shown in Figures 3.a and 3.b for types C-1, Yield-controlled Four Legged and C-2, Yield-controlled T intersections.

Figure 3.a shows the approach sight distance triangles in dark shade and the departure triangle in light shade. Within the approaching sight distance triangle Point A is located in the center of the minor street approach lane. The driver should be able to clearly see from Point A, a distance equal to 25 ft from C1. At Yield-controlled T intersections (shown in Figure 3.b) on page 4, the recommended distance from Point A to C1 is 80 ft.

The departure sightdistance triangle (shown as the light shaded area) at both types of yield controlled intersection is similar to the site distance triangle at stop controlled intersections (Type B). The driver's decision point or Point A is located in the center of the minor street approach lane, 14-feet from the edge of the major road's traveled way. The traveled way is the portion of the road intended for the movement of vehicles and bicycles, exclusive of shoulders and turning lanes. Point B is located on the center of the major street approach through lane (or at the center of the major street approach if more than one lane exists), a specific distance to the left and to the right of Points C1 and C2. This distance is the recommended sight distance, which can be found in Table 2.

Although it is not typical to do so, if a parking lane exists on the major street it may be excluded from the traveled way in special cases. Usually these are cases where volumes and speeds are low and therefore the overall safety risk at the intersection is considered low.

Sight Distance Figure 3A and Sight Distance Figure 3B

Type D - Yield Controlled Intersections

At signalized intersections and signalized driveways, in order to turn right on red, drivers should be able to clearly see vehicles approaching from the left; the applicable sight distance triangle is the shaded area bounded by the A-B, B-C1, and A-C1 setback lines show in Figure 2. Sight distance (B-C1) are summarized in Table 2.

Type E1 through E4 - Driveways not Controlled by Traffic Signals

Driveways not controlled by traffic signals operate as Type B, Stop-Controlled Intersections, therefore, the applicable sight distance triangles are shown in Figure 2. For driveways Type E1, Point A is located 10 ft from the edge of the major route's traveled way. For driveway Types E2 through E4, Point A is located 14 ft from the edge of the major route's traveled way. Sight distances values (B-C1, B-C2) are summarized in Table 2.

Type F - Intersections and Driveways not Covered in Types A-E.

The sight distance triangle for intersections and driveways that do not fit any of the types previously described are to be analyzed on a case by case basis.

Public Works
Engineering
Mon-Fri, 8 a.m. to 5 p.m.
123 5th Avenue, Kirkland WA 98033
Operations & Maintenance
Mon-Fri, 6:30 a.m.-3:30 p.m.
915 8th St, Kirkland WA 98033

General Inquiries
E-mail: publicworks@kirklandwa.gov
Engineering: T. 425.587.3800 | F. 425.587.3807
Operations & Maintenance: T. 425.587.3900 | F. 425.587.3902