All streets which are designed primarily for the movement of vehicular traffic shall conform to the following requirements at the minimum.
(A) Classification of streets. Four basic street classifications shall be observed by developers: expressways; arterials; collectors; and minor streets. Each class is fully defined in § 153.020.
(B) Street standards. The following standards shall apply to 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 proper drainage for storm water, and produce 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.
(3) Street names. Streets which are obviously in alignment with existing streets shall bear the names of the existing streets. Street names shall not duplicate or closely approximate the names of existing streets in the county. Street name signs of a type in use throughout the city and county shall be erected by the developer at all intersections. Temporary street signs and lot addresses shall be erected on all streets and lots under construction to facilitate first responders in the event of an emergency. Permanent street signs shall be required when the first building on the street obtains a certificate of occupancy.
(4) Partial subdivision. Where a development plan includes only a site plan for part of the tract owned or intended for development by the developer, an overall plan of the proposed street system for the remaining portion shall be prepared by the developer and submitted to the Planning Commission for review and action.
(5) Planning for conflicting traffic or land use. Whenever the proposed development contains, or is adjacent to a railroad, arterial street, or other conflicting land use, 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) New partial streets and reserve strips. New partial streets and reserve strips shall not be permitted, except where essential to reasonable development of a tract and where satisfactory assurance for dedication of the remaining part of the street can be secured. No reserve strips shall be permitted unless the Planning Commission gives its express permission.
(7) Existing partial streets. Whenever a proposed development borders an existing partial street, the other part of the street shall generally be plotted within the proposed development.
(8) 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. Temporary turnarounds may be required at the end of stub streets.
(9) Oversize improvements. Whenever street rights-of-way or other improvements are required in excess of what is needed to meet the demands of the development being considered, the Planning Commission should require dedication or improvement costs of the developer only to the extent of the development requirements. The Planning Commission may encourage other appropriate entities to finance the acquisition or costs of the additional improvements.
(10) Special street types. Permanent dead-end streets shall be prohibited. Temporary dead-end streets shall be permitted as part of a continuing street plan only if the temporary turnaround is designed to the satisfaction of the Planning Commission.
(11) Alleys. Alleys may be required if other provisions cannot be made for adequate service access. The minimum widths for alleys shall be 20 feet for the right-of-way and 18 feet for the pavement width.
(12) Private streets. Private streets, where permitted, shall be designed and constructed according to the standards for minor streets in these regulations. Such streets shall be maintained by a mechanism which provides for equitable common responsibility for street maintenance and repair. All recorded plats with private streets shall note the details of the maintenance responsibilities of the property owners abutting the street.
(13) Rural residential streets. Rural residential streets shall be built to county road standards with a minimum pavement width and right-of-way that meets the standards for minor streets in these regulations. The need for curbs, gutters, and sidewalks shall be determined by the Planning Commission on a case-by-case basis depending on anticipated traffic volume and increased storm water runoff.
(C) Street rights-of-way and grades. Shall be as follows.
Street Classification | Min. R.O.W.* | Max. Grade** | Min. Grade |
Alleys | 20' | 12.0% | 0.5% |
Arterials | 80' | 5.0% | 0.5% |
Collectors | 60' | 10.0% | 0.5% |
Expressways | 120' | 5.0% | 0.5% |
Minors | 50' | 12.0% | 0.5% |
*Additional right-of-way may be required whenever a proposed development 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 Planning 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 as follows:
Street Classification | *Horiz. Curve Radius | **Stop Sight Dist. | Crest Curves | Sag Curves |
Street Classification | *Horiz. Curve Radius | **Stop Sight Dist. | Crest Curves | Sag Curves |
Arterials | 573' | 325' | L = 50A | L = 50A |
Collectors | 500' | 250' | L = 45A; 100' min | L = 60A; 100' min |
Expressways | 1,146' | 550' | L = 80A | L = 70A |
Minor, continuing | 100' | 150' | L = 22A; 100' min | L = 35A; 100' min. |
Alleys | 100' | N.A. | N.A. | |
Cul-de-sac | 100' | 1500' | L = 22A; 100' min. | L = 35A; 100' min |
Marginal Access | 150' | 150' | L = 22A; 100' min | L = 35A; 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 55 mph design speed was assumed for expressways, 40 mph for arterials, 30 mph for collectors, and 20 mph for all minor streets. Design must comply with the most recent AASHTO policy: “A Policy on Geometric Design of Highways and Streets”. **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. Design must comply with the most recent AASHTO policy: “A Policy on Geometric Design of Highways and Streets”. ***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' min. 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 street shall be laid out either directly opposite one another or with a minimum offset of 125 feet between their centerlines. For minor and collector streets, consideration should be given to “T” 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 spaced at closer intervals up to 200 feet. 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 feet separation. When through streets cross 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 100 feet or more to the arterials or collector streets.
(5) Excessive grades at intersections. Where the grade of any street exceeds 3% at the approach to an intersection, a leveling area of 3% or less shall be provided for a distance of 50 feet from the intersection of street centerlines. 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.
Street Classification | Distance Along Through Street | Distance Along Stop Street |
Street Classification | Distance Along Through Street | Distance Along Stop Street |
Arterials | 625' | 35' |
Collectors | 500' | 30' |
Expressways | N.A. | N.A. |
All minors, ex. below | 250' | 25' |
Alleys | N.A. | N.A. |
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.
(Prior Code, § 74.710) (Ord. passed 3- -1995; Ord. passed 10- -2005; Ord. 2018-03, passed 2-14-2018; Ord. passed 1- -2020)