(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 and comprehensive plans, all streets shall be designed according to the geometric standards set forth in these regulations.
(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 Appendix A, Tables 1 and 2 and Appendix B, (Figure 1) for average dimensions by Functional Classification). 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.
(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: minor collectors and locals.
(C) Interpretation of design tables. Tables 1 and 2 (See Appendix A) and Figure 1 (See Appendix B) represent average conditions and are included in these regulations to illustrate the hierarchy of functional classification. Tables 3 and 4 (See Appendix A) 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:
(1) Definitions of terrain classification are:
(a) LEVEL. Cross slopes range of 0% to 8%.
(b) ROLLING. Cross slopes range of 8.1 % and over.
(2) Definitions of density classification in terms of gross land area are:
(a) LOW. Two or less dwelling units per acre.
(b) MEDIUM. Two and one-tenth or six dwelling units per acre.
(c) HIGH. Over six dwelling units per acre.
(D) Design traffic volumes. The design hourly volume, DHV, or average daily traffic, ADT, is accepted basis for design. In rural areas the Town Engineer may amend the design standards as determined by traffic demand analysis. 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 for streets serving commercial and industrial areas and the Town Engineer is required to give special attention to these areas.
(E) Design speed. Design speeds are not a major factor for urban residential local and minor collector design. As a general rule, the same rule can be applied to rural low volume roads in subdivision design. The slight distances and curve radii in Tables 3 and 4 (See Appendix A) are commensurate with average acceptable design speeds.
(F) Vertical grades.
(1) Drainage design may become critical where grades exceed 4%. For this reason, grade slower than the suggested tabular values 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 0.5%.
(2) The maximum grade on the approach leg of any intersection shall not exceed 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 55 miles per hour. Where superelevation is used, street curves should be designed for a maximum superelevation rate of:
(1) Urban: 0.04 to 0.06 foot per foot; and
(2) Rural: 0.08 to 0.12 foot per foot.
(H) Horizontal alinement. Minimum centerline radii for horizontal curves shall be as specified in Tables 3 and 4 (See Appendix A). The minimum tangent between reverse curves shall be:
(1) Residential Local: 100 feet;
(2) Residential Minor: 150 feet; and
(3) Commercial/Industrial Collector: 200 feet.
(I) Intersections.
(1) 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 Administrator 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.
(2) The minimum intersection angle shall be 75.
(3) 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.
(4) 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.
(J) Culs-de-sac.
(1) 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 difficult access or are otherwise unsuitable for normal subdividing. However, a 48-foot pavement shall be required in all cases under this special provision. No culs-de-sac are allowed on residential collectors.
(2) The minimum radii for culs-de-sac shall be as follows:
(a) Local: right-of-way or outside, 50 feet; back-to-back of curb, 38 feet;
(b) Commercial/Industrial: right-of- way or outside, 60 feet; back-to-back of curb, 50 feet.
(K) Auxiliary lanes. The Town Engineer shall require construction of parking and turning lanes and transitional tapers where warranted.
(L) Sidewalks. Sidewalks shall be provided along both sides of streets used for pedestrian access to schools located in commercial areas. In medium density residential areas, the Commission may allow for a sidewalk on one side only. Minimum thickness shall be four inches portland cement concrete.
(M) Subgrades and pavements.
(1) Specifications for construction and materials shall be as set forth in the applicable sections of Standard Specifications of the Indiana State Highway Commission. All pavements shall be constructed on compacted subgrade.
(2) Rigid pavements (air-entrained plain cement concrete) shall meet the following minimum requirements:
(a) Pavement thickness: 6 inches on local streets; 7 inches on residential collector streets; 8 inches on commercial/industrial collector streets;
(b) Contraction joints: placed at a spacing of 20 feet or less; placed at every catch basin and manhole in line of pavement; extend throughout side strips and curbs to full width of pavement.
(c) Expansion joints: with approved dowel bar assembly, shall be placed at intersections; where shown on plans.
(3) (a) Flexible pavements may be used. For full depth hot asphaltic concrete or hot asphalt emulsion, the minimum pavement thickness shall be:
1. Seven and one-half inches on local streets;
2. Nine and one-half inches on residential collector streets;
3. Eleven and one-half inches on commercial/industrial collector streets; and
4. Special design on all other streets.
(b) In lieu of full depth asphalt construction, conventional flexible pavements may be used, provided, however, that they meet the following minimum requirements:
1. In no case shall the maximum lift exceed 32 inches;
2. Local Streets: 3 inches HAC on 8 inches of compacted aggregate base;
3. Collector Streets: 3 inches HAC on 8 inches of compacted aggregate base. Commercial and Industrial Collectors may require higher standards.
(Ord. - -, passed - -80)