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The following standards apply to public and private streets within the zone:

A. Street Grades: The maximum allowed street grade is fifteen percent (15%).

B. Intersections: Roads shall intersect at ninety-degree (90°) angles.

C. Intersection Spacing: Intersections should be spaced far enough apart so that the traffic stopped to make left turns at one intersection does not interfere with traffic movements at the adjacent intersections.

1. On low-volume streets such as access roads to minor collectors or minor collectors to minor collectors, the minimum spacing distance is one hundred twenty-five feet (125');

2. For minor collectors to major collectors, the minimum spacing distance is two hundred fifty feet (250').

D. Design Speed: The design of geometric features such as horizontal and vertical alignment will depend on the design speed selected for each street. The design speed is primarily determined by the street function and classification and is the maximum speed for safe and comfortable operation of a vehicle. Other than a major collector, all streets in hillside areas are classified as low speed streets (thirty-five (35) miles per hour or less).

Street Design Classification

Design Speed

Posted Speed

Minor collector

30

30

Local road

25 – 30

25

Hillside local

25

25

Hillside access

25

25

E. Clear Sight Distance at Intersections: Adequate, clear sight distance is required at intersections, as follows:

Posted Speed of Higher Order Road

Minimum Y

Desired Y

20

210

240

25

260

300

30

310

380

35

365

475

F. Vertical Curves and Intersection Relationship: The vertical alignment of residential streets shall comply with latest editions of AASHTO geometric design of highways and streets. See table below for listing of pertinent design criteria:

Minimum Length of Vertical Curves

Design Speed

Crest “K” Value

Sag “K” Value

20

10

20

25

20

30

30

30

40

35

40

50

L = KA (for minimum sight distance on a vertical curve).

L = Length of vertical curve for proper sight distance.

A = Algebraic difference in grade.

Vertical alignment with the intersection is also of special nature, and design alternatives may be required. As a guideline, the approach area where vehicles stop while waiting to enter an intersection shall not exceed four (4%) to five percent (5%) from the gutter line of the street being intersected for a distance of fifty feet (50'), though a range of fifty feet (50') to one hundred feet (100') is more desirable. This applies to all intersections, except those intersections where both intersecting streets are minor collectors. The landing area for a minor collector shall be designed for a grade of two percent (2%) to three percent (3%) for a distance of one hundred feet (100').

G. Safe Stopping Sight Distance: The minimum sight distance to be provided before a stop is required is included in the table below:

Design Speed

Computed

Recommended Distance

Add-On for 15% Grade

20

106.7

125

20

25

146.5

150

36

30

195.7

200

64

35

248.4

250

95

H. Horizontal Curves: The minimum centerline radius for horizontal curves on low-speed residential streets is:

Minimum Centerline Radius

Street Classification or Speed

Curve Radius in Feet

Private streets

50 – 100

20 mph

100 – 150

25 mph

185

30 mph

310

I. Street Cross-Section Standards: The requirements for street cross-section configurations are based on the following factors:

1. Traffic capacity;

2. Design speed;

3. Projected traffic;

4. Designs to reduce scarring.

J. Alternate road cross sections, such as grade separated streets, may be used if applicable safety and traffic standards are met.

K. Elimination of sidewalk on one side of the road may be approved when elimination of one (1) sidewalk can appreciably reduce the amount of hillside disturbance. Other considerations may also warrant its elimination. When one (1) sidewalk is eliminated, the remaining sidewalk shall be increased by one foot (1') in width.

L. The following table sets forth the requirements for street standards for single-family residential development.

Street Cross-Section Standards for Single-Family Residential

Maximum Grade

Street Classification

Width ROW

Width TBC

Pavement Width

Width Sidewalk

ADT

12%

Minor collector

60'

50'

45'

5'

1,500 – 3,500

15%

Local road

50'

40'

35'

4'

750 – 1,500

15%

Hillside local

45'

35'

30'

4'

150 – 750

15%

Hillside access

41'

31'

26'

4'

0 – 150

(Ord. 2019-10-002, 10-10-2019)