A. Design: The arrangement, type, extent, width, grade, and location of all streets must be considered in their relation to existing and planned streets, topographical conditions, public convenience and safety, and the proposed uses of the land to be served by them.
1. Design Specifications: Roads must meet the design specifications in table 1 of this section.
2. Termination Of Street: Where streets terminate, either a cul-de-sac or "T" turnaround must be provided at the terminus. Cul-de-sacs and "T" turnarounds must conform to the design specifications in table 1 of this section.
3. Public Or Private Streets: All streets must either be dedicated to the public or be private streets to be owned and maintained by an approved property owners' association.
4. Residential Driveways: Residential driveways must not have direct access to primary highways. Any vehicular access onto a state highway must be approved by the Montana department of transportation.
5. Local Streets: Local streets must be designed so as to discourage through traffic.
6. Frontage Roads: Whenever a subdivision abuts or contains an existing or proposed arterial highway or major thoroughfare, the governing body may require frontage roads or other treatment as may be necessary to adequately protect residential properties and to separate arterial and local traffic.
7. Half Streets: Half streets are prohibited except when they are essential to the development of the subdivision and when the governing body is satisfied that the other half of the street will be dedicated to the public when the adjoining property is subdivided. When an existing half street is adjacent to a tract to be subdivided, the other half of the street must be platted within the new subdivision.
8. Alignment: The alignment of all streets and roads must provide adequate sight distances.
9. Intersections: The following requirements apply to intersections:
a. Streets must intersect at ninety degree (90o) angles except when topography prohibits this alignment. In no case may the angle of an intersection be less than sixty degrees (60o) to the centerline of the roadway being intersected.
b. Two (2) streets meeting a third street from opposite sides must be offset at least one hundred twenty five feet (125') for local roads and three hundred feet (300') for arterials or collectors.
c. No more than two (2) streets may intersect at one point.
d. Intersections of local streets with major arterials or highways must be avoided.
e. Intersections must be designed to provide adequate visibility for traffic safety based on the designed operating speeds of the intersecting roadways.
f. Hilltop intersections are prohibited, unless no alternatives exist. Intersections on local roads within one hundred feet (100') of a hilltop are prohibited. Intersections on arterial and collector roads within two hundred feet (200') of a hilltop are prohibited. If no alternative to a hilltop intersection exists, additional traffic control devices will be required.
g. The grade of approaches to major highways may not exceed five percent (5%).
10. Names: Names of new streets or roads aligned with existing streets must be the same as those of the existing streets. Proposed street names may not duplicate or cause confusion with existing street names.
11. Proposed Road Plans And Profiles: Proposed road plans and profiles as required by section 12-3-5 of this title are subject to approval by the public works director or road department superintendent.
B. Improvements:
1. Specifications And Standards: All roadway improvements including pavement, curbs, gutters, sidewalks, and drainage must be constructed in accordance with the specifications and standards prescribed in this title using materials approved by the governing body in consultation with and upon the advice of the public works director or road department superintendent.
2. Roadway Subgrades: Roadway subgrades must be free of topsoil, sod, vegetation or organic matter, soft clay, and other substandard materials. Subgrades must be properly rolled, shaped, and compacted, and must be approved by the public works director or road department superintendent and governing body.
3. Design: Streets and roads must be designed to ensure proper drainage. This may require surface crowning, culverts, curbs and gutters, drainage swales and storm drains.
4. Access From Public Road To Subdivision: Where access from a public road to the subdivision will cross properties not owned by the subdivider, the subdivider must obtain proper easements of sufficient width to satisfy the requirements of table 1 of this section.
b. The location of any road easement must be shown on the plat or on a supplemental map. The existence of easements must be noted on the face of the final plat and on any deeds or other instruments conveying lots within the subdivision.
5. Trees And Vegetation: Existing trees and other vegetation must be preserved whenever possible. Plantings may be required for buffering, screening, or prevention of soil erosion and are subject to approval by the governing body.
6. Streetlights: Streetlights will be required in subdivisions proposed within or adjacent to areas with existing street lighting. Street lighting may be required in other areas when necessary to protect public safety.
7. Street Or Road Signs And Traffic Control Devices: Street or road signs and traffic control devices of the size, shape, and height approved by the governing body must be placed at all intersections. Traffic control devices must conform to the standards contained in the manual on uniform control devices available from the Montana department of transportation.
8. Mail Delivery: When required by the United States postal service, the developer must provide an off street area for mail delivery.
C. Table 1, Road Design Standards For Subdivisions:
TABLE 1 ROAD DESIGN STANDARDS FOR SUBDIVISIONS | ||
Minimum Design Standards | Minor Collector
| Local Road |
Minimum right of way width Level terrain Hilly terrain | 60 feet | 50 feet 60 feet |
Minimum roadway width1 | 26 feet | 24 feet |
Minimum curb radius or edge of pavement at intersections | 25 feet | 15 feet |
Maximum grades | 8 percent | 10 percent |
Approaches onto public roads Minimum sight distance Minimum width Maximum grade for 20 feet | 200 feet 135 feet 5 percent | 150 feet 30 feet 5 percent |
Curvature2 Design speed Maximum curve Minimum radius | 30 mph 23 249 feet | 20 mph 53.5 107 feet |
Cul-de-sacs/Turnarounds Maximum road length Cul-de-sac: minimum outside right of way radius Cul-de-sac: minimum outside roadway radius "T" turnaround: backup lengths (2 required) | -- -- -- -- | 1,000 feet 40 feet 35 feet 30 feet each |
New bridges3 Curb to curb widths Design load capacity Vertical clearance | 26 feet 20 tons 14.5 feet | 24 feet 206 tons 14.5 feet |
Notes:
1. Where parking will be permitted add 8 feet on each side. If guardrail installation is required or a shoulder is desired, add 2 feet to each side of roadway.
2. Curvature is based on a super elevation of .08/ft.
3. Width of the bridge roadway surface should match the width of the roadway system it joins.
Notes
| 1 | 1. Section 12-14-11 of this title contains a model road access easement. |