All streets which are designed primarily for the movement of vehicular traffic shall conform to the following requirements.
(A) Classification of streets and required pavements.
(1) Five basic street classifications shall be observed by developers:
Arterial streets, separated pavements, each | 22 feet |
Collector streets (commercial/industrial) | 26 feet |
Collector streets (rural/residential) | 22 feet* |
Local streets (commercial) | 24 feet |
Local streets (rural/residential) | 22 feet |
*Where it is determined that a turn lane(s) is necessary by state or local officials, a minimum of 9 feet of pavement shall be provided for each turn lane, in addition to the travel lanes | |
(2) All streets shall have the following roadway construction standards.
(a) The alignment on all streets should have a centerline run, profile taken and grade figured to construct finished pavement and to establish drainage facilities.
(b) Tangent section of roadway shall have roadway crown of three-sixteenths per foot of roadway and curved sections of roadway to have super elevation in roadway not to exceed 0.01 per foot, depending on length, sharpness of curve and traffic flow. This super elevation to be transitioned from tangent sections to curved section and vice versa, with runoff of curve being of such distance as not to create any water pockets or bumps in roadway. These requirements of constructing roadway to be made in each phase of construction, sub-grade base and finished surface.
(c) The roadway sub-grade should be stripped of all debris, sod, grass, roots and the like. Sub-grade to be finished with suitable materials, soil free of foreign matter, to finished sub-grade elevation, then compacted with rollers and water if needed, to establish suitable sub-grade, prior to adding any base material.
(d) Base material should consist of a packed base consisting of eight inches of dense grade rock. This material should be laid in two equal layers and compacted with at least one 10-ton roller until density of desired percentage is reached for each layer. Water should be added to dense grade aggregate at approximately 7% at point of delivery and additional water added at roadway if so needed for smooth compacted sub-grade. Sub-grade finished elevation should be uniformly maintained as to grade alignment for desired thickness over entire roadway. Results of a compaction test shall be submitted the County Road Supervisor and County Judge/Executive for review and approval
(e) Roadway surface to be Class I surface made according to State Highway Department specifications at a minimum two-inch bituminous base and a one-inch surface to comply with county road ordinance thickness. Surface to be laid in two equal widths of roadway to maintain crown in center of roadway.
(f) The entrance pipe in private entrances to be 15-inch minimum, cross drain or storm sewer to be a minimum of 18 inches. Drainage calculations may be required where roadways/entrances cross natural area drainageways. Such calculations shall be provided by a licensed engineer and shall show flow and drain pipe sizes for specific conditions.
(g) Typical section of roadway should consist of a minimum of 11-foot pavement, three- foot shoulders, two-foot ditch, and four-foot concrete sidewalks built on 3:1 slope each side of centerline. Back slope of ditch in cut section should be so shaped to blend into existing grade or 4:1 slope when practical.
(B) Miscellaneous street standards. The following standards shall apply to miscellaneous street design elements.
(1) Relation to topography. Streets shall be logically related to the topography so as to produce the most usable and properly situated lots, provide the most drainage for storm water and proper grades.
(2) Street continuity. Streets in proposed subdivisions shall generally provide for the continuation of existing or dedicated streets in adjoining or nearby tracts, and provide for connection to adjoining unsubdivided tracts, especially those which would otherwise be landlocked.
(3) Street names. Streets which are obviously in alignment with existing streets shall generally bear the names of the existing streets. Street names shall not duplicate or closely approximate the names of existing streets in the county. Verify street naming with 911 personnel.
(4) Partial subdivision. Where the plan to be submitted includes only a part of the tract owned or intended for development by the developer, a sketch plan of the proposed street system for the unsubdivided portion shall be prepared by the developer and submitted to the Planning Commission.
(5) Planning for conflicting traffic or land use. Whenever the proposed subdivision contains or is adjacent to a railroad right-of-way, arterial street right-of-way, other major rights-of-way or conflicting changes in land uses, the Planning Commission may require marginal access streets, reverse frontage lots, lots with rear service alleys, lots with additional depth, or other such treatment as may be necessary for protection of abutting properties and afford separation of conflicting types of traffic or land use.
(6) Cul-de-sacs. Shall not be longer than 500 feet including the turnaround which shall be provided at the closed end with a right-of-way radius of 50 feet and a transition curve radius of 75 feet for connecting the turnaround with the rest of the street. Longer cul-de-sacs may be permitted because of unusual topographic or other conditions. Temporary turnarounds may be required at the end of stub streets as long as it is retained within the street right-of-way. If temporary turn-arounds are approved for stub streets intended for future extension in conjunction with future adjacent development, each developer shall extend the roadway to the property line within the approved easement.
(7) Oversize improvements. Whenever street rights-of-way or other improvements are required in excess of what is needed to meet the demands of the subdivision plat being considered, the Commission should require dedication or improvement costs of the developer only to the extent of what his or her subdivision needs, and then encourage the other appropriate authorities to finance the acquisition or cost of the additional improvements.
(8) Cuts. In cuts, all tree stumps, boulders, organic material, soft clay, spongy material and other objectionable materials shall be removed to a depth of at least two feet below the graded surface. Rock, when encountered, shall be scarified to a depth of at least 12 inches below the grade surface.
(9) Fills. In fills, all tree stumps, boulders, organic material, soft clay, spongy material and other objectionable material shall be removed to a depth of at least two feet below the natural ground surface. This objectionable matter as well as similar matter from cuts shall be removed from the right-of-way area and disposed of in such a manner that it will not become incorporated in fills or hinder proper operation of the drainage system.
(C) Street rights-of-way and grades. Street rights-of-way and grades shall be as follows:
Street Classification | Min. R.O.W.* Max. Grade** | Min. Grade |
Street Classification | Min. R.O.W.* Max. Grade** | Min. Grade |
Arterials | 80' | 4% |
7% | ||
Collectors | 60' | 4% |
10% | ||
Local (minor) | 50' | 5% |
10% | ||
*Additional right-of-way may be required whenever a proposed subdivision abuts or contains an existing road of inadequate width, or to provide parking space in high density residential districts or nonresidential areas, or to provide drainage easements where streets parallel streams or drainage areas, or for other reasons to promote public safety and convenience. | ||
**The Commission may increase these maximum grades whenever they feel special topographic or other conditions justifies such increase. | ||
(D) Street alignment. The minimum horizontal and vertical alignment on all streets shall be as determined by accepted engineering practice and/or as follows:
Street Classification | *Horizontal Curve Radius Sag Curves | **Stop Sight Distance | Crest Curves ***Vertical Curves |
Street Classification | *Horizontal Curve Radius Sag Curves | **Stop Sight Distance | Crest Curves ***Vertical Curves |
Alleys | 100' | NA | NA |
NA | |||
Arterials | 53' | 275' | L-50A |
L=50A | |||
Collectors | 500' | 175' | L=21A; 100' min. |
L=30A; 125'min. | |||
Cul-de-sac | 50' | 90' | L=7A; 75' min. |
L=12A; 100' min. | |||
Local (minor) | 250' | 90' | L=7A; 75' min. |
L=12A; 100' min. | |||
Marginal access | 150' | 90' | L=7A; 75' min. |
L=12A; 100' min. | |||
*Whenever street centerlines are deflected in excess of one degree, connection shall be made by horizontal curves with a minimum radius at the centerline as noted (a 50 mph design speed was assumed for expressways, and 40 mph for arterials — based on AASHO 1957 policy). | |||
**A minimum safe stopping sight distance, measured from driver’s eye level of four and one-half feet above road surface along centerline of driver’s path to top of object four inches high above road surface, shall be provided as noted in “A Policy on Arterial Highways in Urban Areas,” AASHO, 1957. | |||
***All changes in street grades, having an algebraic difference exceeding 0.5%, shall be connected by vertical curves of a minimum length as noted. In the formula L = minimum length of vertical curve; A = algebraic difference in grades in percent; 100' minimum means minimum acceptable length of curve. | |||
(E) Street intersections. The following standards shall be the minimum for intersection designs.
(1) Number of approaches. Intersections involving more than four basic street legs or approaches shall be prohibited. Merging lanes, deceleration lanes, “Y” intersections and the like, are not included in this prohibition, but are considered as being parts of one street leg or approach.
(2) Angle of street intersection. For a tangent distance of at least 100 feet, measured from the intersection of right-of-way lines, all streets shall intersect at an angle of 90 degrees, where practical, but in no case shall be less than 75 degrees.
(3) Intersection offset. Streets entering opposite sides of another shall be laid out either directly opposite one another or with a minimum for minor and collector streets, consideration should be given to “T” intersections as opposed to four-way intersections.
(4) Intersection spacing. All minor streets intersecting with, and entering the same side of, arterial and collector streets shall be located at least 800 feet apart, measured between centerlines, except that in plans for entire neighborhoods such intersections may be placed at closer intervals. All minor streets intersecting with, and entering the same side of minor streets shall be located at least 200 feet apart, measured between centerlines. Access points from marginal access streets onto arterials and collectors also shall observe the 800-foot separation. When through streets pass through marginal streets and enter a collector or arterial, the marginal access road may be required to be bowed outward at the intersection in order to provide storage space of 400 feet or more to the arterials or collector streets.
(5) Excessive grades at intersections. Where the grade of any street at the approach to an intersection exceeds 3%, a leveling for a distance of 50 feet from the intersection of street centerlines shall occur. Vertical curves shall then be used to connect the intersecting grades.
(6) Intersection sight triangle for crossing. At all intersections, sight triangles shall be provided which will permit vehicles on the designated “Stop” street to safely cross, or turn into, the through street The sight triangles shall be formed by measuring along, and from the intersection of, the street centerlines, and connecting the measured points. The resulting triangles must lie wholly within the street rights-of-way. The following distances shall be measured along the centerlines:
Street Classifications | Distance Along Through Streets | Distance Along Stop Streets |
All minors, except below | 250' | 25' |
Alleys | NA | NA |
Arterials | 625' | 35' |
Collectors | 500' | 30' |
Cul-de-sacs | 200' | 25' |
Marginal access | 200' | 25' |
(7) Minimum property line radii. For street intersections, the minimum radius at property line shall be 20 feet for all streets, unless sound engineering practice dictates otherwise.
(F) Street extensions.
(1) The street layout of the proposed subdivision shall provide for the continuation or projection of streets already existing in areas adjacent to the area being subdivided unless the Planning Commission deems such continuation or extension undesirable for specific reasons of topography or design. The responsibility for these extensions remains with the developer of the dedicated right-of-way filed with his or her plat. At such time that the development right-of-way and street is accepted by the county, the developer shall be absolved from further responsibility of that road and right-of-way.
(2) Where, in the opinion of the Planning Commission, it is desirable to provide street access to adjoining properties, proposed streets shall be extended by dedication to the boundaries of such properties. Where the Planning Commission deems it necessary, such dead-end streets shall be provided with a temporary turn-around having a radius of at least 50 feet.
(3) The street system for the proposed subdivision shall provide for extending existing streets at the same or greater width, but in no case shall a street extension be of less width than the minimum width required in these regulations for a street in its category.
(Ord. passed 4-1-2003) Penalty, see § 153.99