Section 13
13.0 General: All proposed streets, public or private, shall be designed and constructed to conform with the provisions of this section. Approval of the Board and the Fire Chief of the Town of Newbury concerning minimum requirements for passage of safety/emergency vehicles shall also be received. Please refer to the sketch entitled "Minimum Turning Path for Bus Design Vehicles" detailed in Exhibit J.
13.1 Master Plan : The street system shall conform to the Master Plan of principal streets as adopted in whole or in part by the Board.
13.2 Alignment:
13.2.1 Streets shall be continuous and in alignment with existing streets as far as possible.
13.2.2 Street jogs with centerline offsets of less than 125 feet shall not be allowed.
13.2.3 A tangent based on design speed shall be introduced between horizontal reverse curves on all proposed streets.
13.2.4 Approval of the general development street plan shall be required before allowing construction of small integral phases of the plan.
13.3 Intersections: When a street, public or private, leading from a subdivision is proposed to intersect an existing Town street, the entire intersection shall be examined for safety. The Town shall place a STOP sign on the subdivision street. The driver of the stopped vehicle must be able to see enough of the existing street to turn or cross before a vehicle on it from either direction reaches the intersection or overtakes him. To establish and preserve adequate safe sight distance, the following provisions shall be required of the subdivider:
13.3.1 Right-Angle: Except where it is unsuitable because of the character of the land, streets shall intersect so that within 75 feet of the intersection, the street lines shall be at right angles (90 degrees), or in no case shall they be less than 75 degrees.
13.3.2 Grade: The subdivision street within 30 feet of the edge of the existing street pavement or proposed subdivision street shall be at a 2% grade upward when approaching the existing street.
13.3.3 Sight Distance: The safe sight distance for the selected design vehicle (a single-unit truck, 30 feet long) is 13 times the posted speed of the existing town road or subdivision street (e.g., 30 mph = 390 feet; 35 mph = 455 feet). (Intersections with State of NH roads require an all season safe sight distance of 400 feet).
13.3.4 Obstructions: The eye of the driver of a stopped passenger car at 3.5 feet above
the street must be able to see the top of an approaching vehicle at 4.25 feet above the street at the above safe sight distance without obstruction. No structure, vehicle parking, trees or plantings shall impair corner visibility. A "Sight Line Easement"/Deed Restriction shall be imposed on the corner lots controlled by the subdivider adjacent to the intersection to preserve the above safe sight distances; the Easement/Deed Restriction shall provide the Town the right to trim back or remove any impairment to the required visibility at the lot owner's expense.
13.3.5 Rounded Property Lines: Property lines at street intersections shall be rounded to provide a property line radius of not less than 30 feet.
13.3.6 Rounded Pavement Edges: At all private and public street intersections, edges of the pavement, traveled way, or curb lines shall be rounded with large enough radii to allow safe passage of "emergency vehicles" as defined by the template, "Minimum Turning Path for Bus Design Vehicle".
13.4 Guardrail: Guardrail will be required where slopes extend more than 10 feet from the height of the break in shoulder to the original grade on a 2:1 slope or in other hazardous areas which are determined by the Road Agent and the Board. Where guardrail is required, place face of guardrail at old "Break in Shoulder" and add 18 inches to shoulder construction to a new "Break in Shoulder" to stabilize guardrail posts. (See Typical Cross Section).
13.5 Right-of-Way
13.5.1 Public Road, Immediate or Future: Any ROW intended to be immediately or in the foreseeable future deeded to the Town within a subdivision shall be clearly indicated by the two sidelines on the Plat and the area of such ROW subtracted from the land to be subdivided. The width between the two ROW sidelines shall be as specified under "Standards for Street Design" in Section 13.11. This type of ROW will divide the land to be subdivided.
13.5.1 Permanently Private Road: Any ROW that is never intended to be deeded to the Town shall be clearly shown on the Plat as a single centerline and shall be considered as having no width which is subtractable from the land to be subdivided. This type of ROW need not divide proposed lots through which it travels to provide legal access to lots further on in the subdivision.
13.6 Covenant to Release Town etc. from Furnishing Public Streets: If the owner of the land represents to the Board, and the Board agrees, that he does not now desire or require public streets or roads within the subdivision for all or any portion of the land, he shall deliver to the Board for recording a signed Covenant entitled "Covenant Relating to Release of Town of Newbury from furnishing certain facilities in proposed subdivision of land, Newbury, NH" (Exhibit B of these regulations), and if such services are later desired or required, they shall be constructed and installed without cost to the Town in accordance with the regulations then current covering such work. Furthermore, such covenant shall become a part of every deed of transfer within the proposed subdivision.
13.7 Utilities: It is recommended that all electric, telephone, cable, and other overhead lines be placed underground.
13.8 Harmony with Topography: Street and lot pattern design shall give due consideration to contours and natural features of the land, where practical, within the standards set forth in the Zoning Ordinance. Aesthetic values shall be considered rather than rigid straight-line, city block layout of streets and roads.
13.9 Plantings:The Board may require planting within the street right-of-way in those subdivisions where, due to the nature and character of the land, it would be appropriate, and planting shall be indicated on the Plat. The Tree Warden shall recommend to the Board, when requested, the specifications for such plantings.
13.10 Dead-End Streets: In general dead-end streets are discouraged and multiaccess streets are encouraged.
13.10.1 Length Measurement: In determining the overall length of a dead-end street, the street shall be measured from each terminal point to the first intersection of the street with a through street, i.e. the entrance. The terminal point of a loop shall be that point which is equidistant from the entrance. The length in a system of dead-end streets shall be the greatest length measured.
13.10.2 Length: The maximum length of a dead-end street shall be fifteen hundred (1,500) feet.
13.10.3 Special Case Loop Road: A dead-end street that loops back to join itself within two hundred fifty feet (250') of its junction with a through street shall not be considered to be a dead end street.
13.10.4 Signage: All dead-end streets shall have a sign erected at the entrance warning that the street is a dead end or not a through street.
13.10.5 Turnarounds: Streets within a subdivision shall be coordinated with existing and other planned streets. In the event that the Board approves a dead-end street, it shall terminate in either of the following types of turnaround:
Cul-de-Sac: Cul-de-Sac design shall be either "Circular", "Teardrop", or "Reverse P" as detailed in Exhibits E, F and G respectively. The roadway width of a cul-de-sac shall be 20 feet. Drainage of the unsurfaced center of the Cul-de-Sac shall be provided by adequate means including culvert(s) leading to the outside of the Cul-de-Sac.
Hammerhead "T" Type: Hammerhead "T" type turnarounds shall be 85 feet across and at least 20 feet wide. Drainage around the hammerhead shall be adequate.
Grades on Turnarounds: The grade on the turnaround and on 30 feet of its approach straightaway shall be no greater than 2% to enable winter plowing.
13.10.6 Isolation: A permanent dead-end street shall be isolated by not being brought to the property boundary line, but shall be placed so that the lots abutting on the end of the street are contiguous with the property line of the subdivision. (This assures for a permanently dead-end street that the smallest size street based on the average daily vehicular traffic and number of housing units can be selected from the table "Classification of Streets" provided in Section 13.11 since through traffic is eliminated which could necessitate selection of a larger size street.)
13.10.7 Through Circulation: The Board shall ensure that there is adequate through circulation when needed as determined by the Board for secondary emergency vehicle access and overall traffic circulation. Traffic circulation patterns for service and local streets shall be designed to discourage through traffic from short-cutting through residential neighborhoods. The size of street needed within a subdivision is based on traffic to be generated by the development plus through traffic anticipated to use the street from outside the development. Whenever provision is made for extending a street through to an adjoining property, the extent of outside or through traffic needs to be accounted for in determining the appropriate size street to develop within the subdivision.
See Figure 13.1
13.11 Classification of Streets
Classification standards for street design shall be as set forth below (See "Typical Cross Section with Open Drainage and Typical Cross Section with Closed Drainage").
STANDARDS FOR STREET DESIGN
Service1 Local Collector Arterial
Average Daily Vehicular Traffic2 1-40 1-240 241-400 400+
Number of Housing Units 1- 5 1- 30 31- 50 50+
Min. Traveled Surface Width (ft) 14 20 24 26
Min. Shoulder Width (ft) each side12 2 3 3 4
Min. Distance between Shoulder -
Break Points (ft) 18 24 30 34
Base Courses - Sand (in)3 4 6 6 6
- Gravel (in) 4 12 12 14
- Crushed Gravel (in) 4 6 6 6
Total Depth of Base Courses (in) 12 24 24 26
Pavement Surface Material10,12,13 Opt. P.B.Opt. Bit.Con. Bit.Con.
Ditch Line to Ditch Line (ft)4 26 32 40 46
Min. Right-of-Way (ft)5 40 50 50 60
Design Speed for Street (MPH)6 20 30 30 35
Crest Vertical Curve "K" Factor7 10 30 30 55
Sag Vertical Curve "K" Factor7,11 18 40 40 55
Min. Vertical Curve Length (ft) 60 200 200 200
Min. Horizontal Curve Radii to -
Centerline of street (ft)8,9 140 325 325 400
Max. Curve Banking Cross Slope 4% 4% 4% 4%
Max. Profile Grade9,10 10% 8% 8% 6%
13.11.1 Footnotes for the above table
- Service street standards may only be used on application to and with approval of the Board. Extra gravel as determined by the Road Agent shall be required when subgrade is on high silt material or clay.
- Shall be traffic anticipated 20 years into the future (Assuming 8 trips per day per dwelling unit.) Refer to Section 13.10.4.
- Gravel may be substituted for sand.
- Ditch lines located at bottom of Base Courses on "subgrade" and on an assumed 4:1 side slope from break point to ditch line. See Exhibit K. This influences amount of ROW.
- The ROW dimension shall be measured perpendicular to straight-line sections and radial to curved sections. The right-of-way shall include five (5) feet more than the toe of the side slope and the top of the back slope (see Typical Cross Section).
- Establishment of a design speed controls vertical and horizontal curves.
- Multiply the appropriate Vertical Curve "K" Factor by the algebraic difference in grades in percent to obtain the minimum length of vertical curve for the street's profile. Unsymmetrical vertical curves will not be accepted by the Board.
- Radii based upon the design speed for the street.
- When horizontal radii within ten percent of the minimum are combined with profile grades within ten percent of maximum, one or the other shall be improved by twenty percent to preserve safety.
- Profile grades equal to or over eight (8) percent shall be paved with bituminous concrete. Also, provide a 200 foot paved run-out on each end. "Opt" equals optional. "P.B. Opt" equals Planning Board's option or determination on requirement for bituminous concrete surface. "Bit Conc." equals bituminous concrete obligatory.
- Use 'Service Street' 'K' Factor for stop intersections.
- Streets designed with closed drainage shall have a paved surface curb to curb.
- Any road proposed to be maintained by the Town shall be paved.
13.12 Marking of Proposed Streets: At the earliest practical stage during the application, the subdivider shall place on the ground clearly observable survey stakes with ribbons marking the center line of all proposed streets.
13.13 Alteration of Gradient: The Board may modify the maximum and minimum gradient for short lengths of street where, in the judgment of the Board, existing topographic
conditions or the preservation of natural features indicate that such modification will result in the best subdivision of the land.