(a) Design and Arrangement.
(1) The arrangement of streets in new subdivisions shall make provision for the continuation of the principal existing streets in adjoining areas, or their proper projection where adjoining land is not subdivided, insofar as they may be deemed necessary for public requirements.
(2) The street and alley arrangement shall be such as not to cause hardship to owners of adjoining property when they plat their own land and seek to provide for convenient access to it. Residential streets shall be designed so as to discourage through traffic, but offset streets should be avoided.
(3) The angle of intersection between minor streets and major streets should not vary by more than ten degrees from a right angle. All other streets should intersect each other as near to a right angle as possible, and no intersection of streets at angles of less than seventy degrees shall be permitted.
(4) Residential streets shall be designed to discourage through traffic which may otherwise use secondary or major highways and whose origin and destination are not within the subdivision. Residential streets extending for considerable distance, parallel to any secondary or major street, should be avoided.
(b) Alignment.
(1) Vertical. For main thoroughfares, profile grades shall be connected by vertical curves of a minimum length equivalent to twenty times the algebraic difference between the rates of grade, expressed in feet per hundred; for secondary and minor streets and alleys, fifteen times.
(2) Minimum horizontal. Radii of center line curvature shall be:
Main thoroughfares, twelve degrees - 475 feet;
Secondary thoroughfares, nineteen degrees - 300 feet;
Minor streets, twenty-eight degrees - 200 feet;
Streets shorter than 500 feet, fifty-eight degrees - 100 feet.
A minimum fifty-foot tangent shall be introduced between traverse curves.
(3) Visibility requirements.
A. Minimum vertical visibility (measured four and one-half feet eye level to tail light eighteen inches above ground level) shall be: 500 feet on main thoroughfares; 300 feet on secondary thoroughfares; 200 feet on minor streets; 100 feet on streets shorter than 500 feet.
B. Minimum horizontal visibility shall be: 500 feet on main thoroughfares, measured on the centerline; 300 feet on secondary thoroughfares, measured on the centerline; 100 feet on all other streets, measured on the centerline.
(c) Street and Alley Width.
(1) Conformance. The width of all major thoroughfares shall conform to the width designated on the Official Thoroughfare Plan.
(2) Widths specified. The minimum right-of-way widths for streets and alleys are as follows:
Type of Street or Way | * Minimum Right-of-way Width (ft.) |
Major streets and highways | variable** |
Secondary or collector streets | 60* |
Minor or local urban streets | 60 |
Rural roads and streets serving low density suburban development | 60 |
Alleys | 20 |
Crosswalk | 10 |
* More right of way may be required where projected traffic counts and/or roadside ditches are used in place of curbs and gutters.
** To be determined by the Planning Commission.
(3) Cul-de-sacs. Each cul-de-sac shall be provided with a turn-around having a minimum right-of-way radius of fifty-six feet. The outside of the road surface within the turn-around right of way shall have a minimum radius of forty-five feet.
(4) Dead-end streets. Streets designated to be dead-ended permanently shall not be permitted. Any dead-end street of a temporary nature, if longer than 200 feet or fronted by existing lots, shall have a surfaced turning area equal in diameter to the width of such street at its termination.
(5) Half streets. Dedication of half streets shall be discouraged. Where there exists a dedicated or platted half street or alley adjacent to the tract being subdivided, the other half shall be platted if deemed necessary by the Commission.
(6) Alleys. Alleys should be avoided in single or two-family districts. They may, however, be required in multiple dwelling developments where they should have a minimum width of twenty feet. Alleys are required in the rear of all commercial and industrial lots if no other provisions are made for adequate service access or for parking. The rights of way of such alleys shall not be less than twenty feet and dead-end alleys shall not be permitted.
(7) Street grades (vertical curves). No street grade shall be less than four-tenths percent and shall not exceed the following with due allowances for reasonable vertical curves:
Main or arterial thoroughfare 5%
Secondary thoroughfare 6%
Minor streets 8%
(8) Street grades (cross-section). The gradients of streets shall be not less than 0.5 percent without curb and gutter and 0.3 percent with curb and gutter. On streets where curbs, gutters and sidewalks are not required, there shall be a berm, the width of which shall be determined by the applicable street cross-section which is a part of the major thoroughfare plan.
(9) Street names. Where new names are required for new streets in unincorporated areas, the names shall meet with the approval of the County Engineer.
(Ord. 1368. Passed 4-6-61; Ord. 146-82. Passed 11-4-82; Ord. 195-96. Passed 11-7-96.)