(A) General design. The arrangement, type, extent, width, grade, materials and location of all streets shall be considered in their relation to existing and planned streets, topographical conditions, maintenance considerations, the delivery of emergency services, public convenience and safety, and the proposed uses of the land to be served by them.
(B) Applicability. All off-site and on-site streets providing the primary access to a proposed subdivision and subdivision lots shall meet the standards contained herein, including those listed in Table 1, except as allowed by variance.
(C) Half streets. Half streets are prohibited, except when they are essential to the development of the subdivision and when the City Council is satisfied that the other half of the street will be dedicated to the public when the neighboring 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.
(D) Frontage accesses. Where a subdivision abuts or contains an existing or proposed arterial or collector street, the subdivider may be required to provide a frontage access with a reservation prohibiting access along the arterial or collector street right-of-way, with screening plantings or other such treatment as may be necessary for the protection of residential properties and to afford separation of through and local traffic.
(E) Dead-end streets. The following provisions apply to dead-end streets.
(1) Dead-end streets are only allowed if they are shared residential drives (50-foot maximum length) or local streets (500-foot maximum length). Measurements shall be made from the edge of the intersecting street right-of-way to the end of the dead-end street or turn-around right-of-way.
(2) Alleys are not allowed to dead-end and must be served by other streets at both ends.
(3) Except for shared residential drives, no dead-end street shall be permitted without an approved turn-around. Where dead-end streets terminate, the developer shall provide either a cul-de-sac bulb or “T” turn-around at the terminus. Modified “T” turn-arounds are also allowed; provided they allow for three-point turn-arounds for the largest Fire Department vehicle. Shared residential drives that share an approach and drive for 50 linear feet or less as measured from the edge of the intersecting street are not subject to the requirement to provide a turnaround area.
(4) Where it is planned that a dead-end street will be extended for a future phase or subdivision, a temporary cul-de-sac bulb or “T” turn-around shall be provided and a right-of-way of appropriate width shall be shown on the preliminary and final plat to the adjoining phase or subdivision property.
(5) Cul-de-sac bulbs and “T” turn-arounds must also conform to the design specifications in Table 1.
(6) Sufficient right-of-way for turn-around areas and associated stormwater drainage facilities shall be provided, which at a minimum shall be consistent with the street right-of-way width.
(F) Multiple access points required. To facilitate access by emergency vehicles and to allow an escape route for occupants in emergency situations, all streets over 500 feet in length and all subdivisions located in high fire hazard areas as determined by the Fire Department or other fire authority shall be designed such that the legal and physical access street(s) serving all lots provide multiple access points to the public transportation network.
(G) Intersections. The following requirements shall apply to street intersections.
(1) Streets shall be laid out so as to intersect as nearly as possible at right angles. No street shall intersect any other street at less than a 75 degree angle.
(2) The intersections of more than two streets at one point shall be avoided, except as described in this division this division (G).
(3) Two streets meeting a third street from opposite sides shall meet at the same point or their centerlines shall be off-set by a minimum of 125 feet for local streets and residential drives and 300 feet for collectors or arterials.
(4) Where any gravel street intersects a hard-surfaced street, the gravel street shall have a hard surface for a minimum of 30 feet from the hard-surfaced street.
(5) Intersection design must provide acceptable visibility for traffic safety as dictated by the designed operating speeds on the individual streets.
(H) Street construction. All streets shall be constructed to the latest edition of the Montana Public Works Standard Specifications.
(I) Street design standards. Streets shall be designed and constructed to the standards outlined in Table 1.
Table 1: Street Design Standards
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Design Criteria | Street Type | ||||
Arterial
|
Collector and Local | Shared | |||
High Density | Low Density | Residential Drive | Alley | ||
Table 1: Street Design Standards
| |||||
Design Criteria | Street Type | ||||
Arterial
|
Collector and Local | Shared | |||
High Density | Low Density | Residential Drive | Alley | ||
Centerline radius on curves | 300 feet | 200 feet | 100 feet | 80 feet | 80 feet |
Curb radius of street at intersections | 35 feet | 25 feet | 25 feet | 15 feet | 15 feet |
Curb and gutter | Required | Required | Required | NA | NA |
Local 500 feet | 50 feet | NA | |||
Maximum grade within 100 feet of intersecting centerline | 2% | 3% | 3% | 5% | 3% |
Maximum street grade | 5% | 8% | 10% | 12% | 8% |
Maximum length of blocks | 500 feet | 500 feet | 500 feet | NA | 500 feet |
Maximum length of dead-end street | NA | Collector: NA | |||
Minimum backup leg lengths from edge of street | NA | NA | 18 feet | NA | NA |
Minimum outside turning radius of cul-de-sac bulb | NA | NA | 30 feet | NA | NA |
Minimum right-of-way width | 80 feet | 60 feet | 60 feet | 30 feet1 | 30 feet |
Minimum street surface width | 30 feet2 | 38 feet | 24 feet | 16 feet | 12 feet |
Sub-base depth | 18 inches | 12 inches | 12 inches | 8 inches | 8 inches |
Surface depth | 6 inches | 4 inches | 4 inches | 3 inches | 3 inches |
Surface material (minimum) | Asphalt | Asphalt | Asphalt | Gravel | Gravel |
Surface base depth | 6 inches | 4 inches | 4 inches | NA | NA |
1 Shared residential driveways are to be located within private easements, not publicly dedicated right-of-ways. 2 Where parking is to be allowed along arterials, additional surface width is required depending upon parking configuration (parallel, diagonal, perpendicular and the like). A minimum of 8 feet of additional width is required on each side of the street where parking is allowed. If parking is not allowed along the arterial, it shall be signed with approved no parking signs. | |||||
(J) Bridges and culverts.
(1) Bridges or culverts shall be provided where drainage channels and waterways intersect any street right-of-way or approach. Guard rails shall also be installed on bridges. The subdivider shall be responsible for the costs of such improvements subject to MCA § 7-14-2204 and other applicable statutes. For any improvements required to be constructed and/or maintained by the Board of County Commissioners, the preliminary plat application shall include the subdivider’s proposal to ensure the improvements are installed in accordance with state law and applicable regulations, along with comments on the proposal from the Board of County Commissioners. All proposals for the installations and related improvements are subject to approval by the Board of County Commissioners and City Council prior to final plat approval.
(2) Bridges and culverts shall be designed by a registered engineer to be appropriately sized in accordance with the drainage.
(3) Bridges shall be constructed to HS25 load standards and shall be the same width as the street.
(4) Bridges within the 100-year floodplain shall be designed so the lowest horizontal chord of the bridge is at least two feet above the base flood elevation.
(5) All bridge and culvert installations shall be approved by the city, which may consult with contracted agents to ensure adequacy.
(6) All bridges within the city are subject to review and approval by the Montana Department of Transportation and are subject to state standards for design and inspection.
(Prior Code, § 11.02.060.130) (Ord. 151, passed 6-20-2016)