Streets must be designed with regard to topography, soil characteristics, natural features, function, clarity of movement and economy of street length. The layout of new streets shall be designed in relation to existing streets. Where deemed appropriate by the Commission, access to existing streets shall be provided. The Commission may require the subdivision to have more than one point of ingress and egress. The arrangement and character of all streets shall conform to the Official Thoroughfare Plan of the county.
(A) Right-of-way. The owners of property to be subdivided on existing streets shall dedicate any additional right-of-way necessary to comply with the minimum standards of the Thoroughfare Plan. Where topography, design features or other conditions necessitate additional right-of-way or easements to permit construction of a street to the established standards for the street, the Commission may require dedication of the right-of-way or establishment of the easements.
(B) Extension of streets. Where the Commission deems appropriate, streets shall be extended to the subdivision boundary line to provide for existing and future traffic circulation.
(C) Dead-end streets. Permanent dead-end streets shall not be permitted. Temporary dead-end streets shall be permitted only as part of a continuing street plan and where more than one lot long must be provided with temporary turn-arounds meeting the specifications in § 156.133.
(D) Alleys. Alleys shall not be permitted in residential subdivisions. The Commission may permit alleys in commercial or industrial subdivisions if it finds that alleys are the best means of serving the subdivision. The alleys shall have a minimum right-of-way width of 20 feet and a minimum pavement width of 16 feet.
Arterial | Collector | Local | Marginal Access Subdivision | |
Arterial | Collector | Local | Marginal Access Subdivision | |
ADT | 1,000 or more | 500 to 999 | 100 to 499 | <100 |
Design speed | 50 mph | 45 mph | 40 mph | 30 mph |
Maximum grade | 8% | 10% | 12% | 12% |
Minimum bridge width | 30 ft. | 30 ft. | 28 ft. | 28 ft. |
Minimum R-O-W width | 100 ft. | 70 ft. | 50 ft. | 40 ft. |
Pavement markings | center line w/no parking zone & edge lines | center line | none | none |
Pavement width | 24 ft. | 22 ft. | 22 ft. | 20 ft. |
Shoulder width | 8 ft. | 6 ft. | 4 ft. | 4 ft. |
Sight distance | ||||
Stopping | 350 ft. | 310 ft. | 275 ft. | 200 ft. |
Intersection | 500 ft. | 450 ft. | 400 ft. | 300 ft. |
NOTES TO TABLE:
(1) The pavement cross slope shall be between 1/4 inch per foot and 3/8 inch per foot. (2) The shoulder cross slope shall be between ½ inch per foot and one inch per foot. (3) The minimum grade shall be 0.10%. (4) For arterial and collector streets, at least 2 feet of the shoulders shall be stone or paved. (5) The right-of-way shall be adequate for construction and maintenance of pavement, shoulders and ditches. The Commission may require an additional right-of-way as it deems necessary for these purposes, or may reduce the required right-of-way widths if the applicant provides justification deemed adequate by the Commission. (6) The pavement widths shown on this table are for streets and roads having a typical shoulder section. For each parking lane, an additional 8 feet of pavement shall be provided, and for curb and gutter an additional 2 feet shall be provided. At least one parking lane shall be provided on all roads with curb and gutter. (7) Residential subdivision streets shall be designed according to the traffic volumes shown on this table assuming 8 trips per lot per day. (8) The minimum outside radius and approach radius of the pavement of a cul-de-sac shall be 50 feet. Cul-de-sac streets shall not exceed 1,000 feet in length, and in no case shall more than 15 lots have frontage on a single cul-de-sac. In all other respects, cul-de-sac streets shall meet all standards for subdivision streets. (9) The minimum outside radius of a temporary turn-around shall be 50 feet. Any turn-around shown on the construction plans shall be installed in conformance with the standards set forth in § 156.133. | ||||
Design Criterion | Standard |
Angle of intersection | 90 degrees (in no case <75 degrees) |
Maximum approach speed | 25 mph |
Maximum number of roads at intersection | 2 (4 approaches) |
Minimum centerline offset of adjacent roads | |
Collector-arterial | 1,320 ft. |
Collector-collector | 600 ft. |
Local-collector | 300 ft. |
Local-local | 200 ft. |
Local-subdivision | 200 ft. |
Subdivision-subdivision | 150 ft. |
Minimum curb radius | |
Collector-collector | 40 ft. |
Local-collector | 30 ft. |
Local-local | 25 ft. |
Local-subdivision | 25 ft. |
Subdivision-subdivision | 25 ft. |
Vertical alignment with intersection | 50% of approach grade |
(G) Vertical alignment. All changes of grade shall be connected by vertical curves of a minimum length equivalent to 85 times the algebraic difference in the rate of grade, expressed in feet per hundred, for arterial streets, 55 times the algebraic difference for collector streets and 35 times the algebraic difference for local and other minor streets. The minimum length of the vertical curve shall be 180 feet for arterial, 120 feet for collectors and 90 feet for local or minor streets.
(H) Half-streets. Dedication of new half-streets shall not be permitted. Where a dedicated or platted half-street is adjacent to a tract being subdivided, the other half of the half-street shall be platted and constructed.
(I) State highways. If any subdivision or any lot therein abuts a state highway, evidence of compliance with all applicable regulations of the State Department of Transportation shall be required.
(J) Improvements. When subdividing property which involves the construction of new streets, the subdivider shall be required to install all improvements specified by the Commission in accordance with this chapter. When a subdivider owns and proposes to subdivide property on only one side of an existing street, the subdivider shall be required to install improvements specified by the Commission in accordance with this chapter for a minimum of one-half of the road and right-of-way width. The Commission may require the additional improvements as it deems necessary to make the existing street suitable for the safe movement of traffic to be generated by the proposed subdivision. When the Commission deems it in the best interest of the county, it may require improvements equivalent in cost to the required half right-of-way improvements to be made over the entire right-of-way or any portion thereof, or it may accept an equivalent amount of money to be used for county street improvements.
(K) Topography and arrangement.
(1) Streets shall be related appropriately to the natural topography. Where appropriate to the topography, streets shall be arranged so as to provide building sites which are at or above the grades of the streets to the maximum practical extent. Grades of streets shall conform as closely as possible to the original topography.
(2) All streets shall be properly integrated with the existing and proposed system of thoroughfares.
(3) All arterial and collector streets shall be properly related to special traffic generators such as industries, business districts, schools, churches and shopping centers; to population densities; and to the pattern of existing and proposed land uses.
(4) Local and subdivision streets shall be laid out to conform as nearly as possible to the topography, to discourage use by through traffic and to permit efficient drainage and utility systems.
(5) Proposed collector streets shall, where the Commission deems appropriate, be extended to the boundary lines of the tract to be subdivided.
(Prior Code, § 8-57) (Ord. 1986-7, passed 10-21-1986)