(A) General. In order to provide for streets of suitable location, width, and improvement to accommodate expected traffic and afford satisfactory access to police, firefighting, snow removal, sanitation, and road-maintenance equipment, and to coordinate street development so as to compose a convenient system, avoid undue hardships to adjoining properties and assure compatibility with long range comprehensive plans, all streets shall be designed according to the geometric standards set forth in these regulations. In furtherance of the comprehensive plan and good planning principles, no subdivision of land shall be permitted that adversely affects the carrying capacity or stability of traffic flow on the adjacent street system.
(B) Principles of design.
(1) Subdivision street design, as a general rule, deals with the design of local and minor collector streets which are part of a functionally classified overall street and road system of an area (see Tables 1 and 2 and Figure l in Appendix for average dimensions by Functional Classifications). In designing and approving subdivision streets, the following factors shall receive consideration:
(a) Safety for both vehicular and pedestrian traffic;
(b) Efficiency of service for all users;
(c) Livability or amenities as affected by traffic elements in the circulation system;
(d) Economy of both construction and use of land.
(e) Carrying capacity of the street system.
(2) Design of major collector and arterial streets shall require special design and approval of the Town Engineer and the following design guidelines are therefore specifically intended for streets within the subdivision (for example, minor collectors and locals).
(C) Interpretation of design tables.
(1) Tables 1 and 2 and Figure 1 represent average conditions and are included in these regulations to illustrate the hierarchy of functional classification. Tables 3 and 4 represent specific design standards for minor collectors and local streets respectively. Design variation or control is based on terrain classification and development density as described below:
(a) Definitions of
TERRAIN classifications are:
1.
LEVEL. Cross slopes range of 0% to 8%.
2.
ROLLING. Cross slopes range of 8.1% to 15%.
3.
HILLY. Cross slope of over 15%.
(b) Definitions of
DENSITY classification in terms of net land area (for example, land area excluding public rights-of-way and easements) are:
1.
LOW. Two or less dwelling units per acre.
2.
MEDIUM. 2.1 to 6.0 dwelling units per acre.
3.
HIGH. Over 6.0 dwelling units per acre.
(2) In the case of areas zoned for office, commercial, or industrial uses, the high density residential classification shall be followed.
(D) Design traffic volumes. The design hourly volume, DHV, or average daily traffic, ADT, is the accepted basis for design. Projected traffic volumes shall be determined using the DHV or ADT traffic volumes as the base and the number of trips generated calculated from Table 6 in the appendix to this chapter. However, the traffic volume usually is not a major criterion in determining the geometric values to be used in designing low volume residential local and minor collector streets. Traffic volumes are a major factor to be considered and the Town Engineer and Commission are required to give special attention to the determination of future volume as it impacts carrying capacity and stability of traffic flow on the town's street system.
(E) Design speed. Design speeds are not a major factor for urban residential local and minor collector design. The sight distances and curve radii in Tables 3 and 4 are commensurate with average acceptable design speeds.
(F) Vertical grades. Drainage design may become critical where grades exceed 4%. For this reason, grades lower than the suggested values in Tables 3 and 4 are encouraged. Commercial and industrial streets shall be held to a maximum grade of 4%. Residential streets shall in no case exceed the tabular values. In order to provide for proper drainage the minimum grade should be held to 1%. The maximum grade on the approach leg of any intersection shall not exceed 5% in hilly terrain and 2% in level terrain.
(G) Superelevation. Superelevation is usually not required in residential areas. It should be considered in commercial and industrial areas and for collector streets where operating speeds may exceed 30 to 35 MPH. Where superelevation is used, street curves should be designed for a maximum superelevation rate of: Urban, 0.04 to 0.06 foot per foot.
(H) Horizontal alignment. Minimum centerline radii for horizontal curves and the minimum stopping sight distance shall be as specified in Tables 3 and 4. The minimum tangent distance between reverse curves shall be:
(1) Residential Local 100 feet
(2) Residential Minor Collector 150
(3) Commercial/Industrial Collector 200
(I) Vertical alignment. All vertical crest and sag curves shall conform to the formula L-50A.
(J) Intersections. Intersections, including median openings, should be designed with adequate corner sight distance. The recommended minimum corner sight distance is 200 feet for local streets and 300 feet for minor collectors. In order to maintain these distances the local Town Engineer or the Technical Committee may recommend regulations to restrict the height of embankment, location of buildings and screening fences and landscaping, and other provisions necessary for intersection sight control. The minimum intersection angle shall be 75°. Closely spaced offset intersections are undesirable. The minimum intersection centerline offset (jog) shall be 150 feet. To accommodate transitional tapers, turning lanes, and other potential roadway design requirements where needed, the Town Engineer may recommend longer offsets. The minimum curb return radius at local streets shall be 15 feet and at residential collector streets 20 feet. The desirable radius is 25 and 30 feet respectively. On commercial and industrial streets the radius shall be 30 feet except where traffic conditions may warrant a smaller radius. The use of three-centered curves may be required in commercial and industrial areas to accommodate the largest vehicles expected.
(K) Cul-de-sacs. The maximum length of a residential local street cul-de-sac shall be 600 feet. Wherever a minor collector street serves exclusively an industrial or commercial area, a cul-de-sac may be allowed and the length may be increased to 1,000 feet. This special provision shall be allowed only in areas which have a difficult access or are otherwise unsuitable for normal subdividing. However, a 48-foot pavement width shall be required in all cases under this special provision. The minimum radii for cul-de-sacs shall be as follows (refer to figure 2):
(1) Local. Right-of-way or outside, radius of 50 feet; back-to-back of curb, radius of 38 feet.
(2) Commercial/industrial. Right-of-way or outside, radius of 60 feet; back-to-back of curb, radius of 50 feet.
(L) Auxiliary lanes. The Town Engineer shall require construction of parking and turning lanes and transitional tapers where warranted.
(M) Sidewalks. Sidewalks shall be provided along both sides of streets used for pedestrian access, such as to schools, parks, or commercial areas. In medium density residential areas, the Commission may allow for a sidewalk on one side only. In very low density areas, where the number of lots per net acre is one or less, no sidewalks are required. Sidewalks shall be constructed of portland cement concrete, at least four inches thick, and four feet wide or five feet wide, as specified in Tables 3 and 4, and placed one foot from the street property line.
(N) Subgrades and pavements.
(1) Minimum specifications for construction and materials shall be as set forth in the applicable sections of Standard Specifications of the Indiana State Highway Commission except where the local government has adopted a different set of standards and specifications, or as required in these regulations.
(2) Rigid pavements (air-entrained plain cement concrete) shall meet the following minimum requirements:
(a) Pavement thickness.
1. Six inches on local streets with low and medium density residential development.
2. Eight inches on local streets with high density residential development and collector streets with residential development.
3. Ten inches on local or minor collector streets with office, commercial, or industrial development.
4. Special design on all major collector and arterial streets, but not less than ten inches.
(b) Contraction joints.
1. Placed at a spacing of 20 feet or less.
2. Placed at every catch basin and manhole in line of pavement.
3. Extend throughout side strips and curbs to fill width of pavement.
(c) Expansion joints.
1. With approved dowel bar assembly, shall be placed at street intersections.
2. Where shown on plans.
(3) Flexible pavements may be used. The minimum pavement thickness shall be:
(a) Local and minor collector residential streets: 8-inch waterbound macadam, 2-inch bituminous coated aggregate, and 1½-inch asphaltic concrete.
(b) Local and minor collector nonresidential collector streets: 8-inch waterbound macadam, 2-inch bituminous coated aggregate, and 2-inch asphaltic concrete.
(c) Special design on all major collector and arterial streets, but not less than the above.
(3) In lieu of fill depth asphalt construction, other flexible pavement types may be used, provided however, that these designs meet the requirements of the Town Engineer. In no case shall the maximum lift exceed three inches.
(O) Curbs. Only barrier (vertical) curbs are permitted and shall be required for all roadways. The typical two-foot curb and gutter section appears in Figure 2 in the Appendix.
(Ord. 93-Z-03, passed 3-8-93; Am. Ord. 95-Z-01, passed 2-13-95)