All streets shall be designed and located so as to be continuous and in alignment with existing streets and with other proposed streets and so as to provide adequate access to all lots in the subdivision via ways that are safe and convenient for travel and so as to satisfy all of the purposes set forth under G.L. c. 41, § 81M. No grant of approval for any definitive subdivision shall occur unless the Planning Board first determines that the adjacent private and public ways to which the subdivision streets are proposed to connect will provide adequate access that is safe and convenient for travel and satisfy all of the purposes set forth under G.L. c. 41, § 81M and Regulation 3.11.
A.
General. Streets shall be designed and constructed so as to be continuous, of uniform width, and in alignment with existing streets and shall conform to the following specific requirements.
B.
Typical street cross-section. Street and roadway construction shall conform to the typical street cross-sections and details shown in Tables 1, 2 & 3 of the Regulations,[1] which shall be considered part of the Regulations.
[1]
Editor's Note: Said tables are included as attachments to this chapter.
C.
Street width of right-of-way. The minimum width of a street right-of-way shall be 50 feet. A greater width may be required for streets that serve commercial or industrial uses.
D.
Street width of pavement. Streets shall be constructed in the manner described herein with a minimum paved surface width of 26 feet for all residential streets and a minimum paved surface width of 32 feet for all commercial and industrial streets. Each street shall be constructed on the center line of the way. The Planning Board may require, for commercial and industrial development, that the traveled way shall be separated by a raised median strip with a width of to be determined by the Planning Board. In this case, the traveled way shall consist of two roadways each with a minimum width of 20 feet or such greater width as the Planning Board may specify.
E.
Projection of streets and easements. Provisions satisfactory to the Planning Board shall be made for the proper projection of streets or for access to adjoining property that is not yet subdivided, including a condition that such a through connection shall not occur without further subdivision approval, including modification of the original subdivision. If such a projection is required, then, except as otherwise provided bylaw, projection of streets shall be included within the street layout and provision made to deed an easement interest to the Town at the time of street acceptance although not constructed. Sufficient easements for construction of the way(s) shall be included in the plans and deeds for abutting lots. Easements shall be located to the property boundary for future utility connections, water main looping, etc., to the satisfaction of the Planning Board and applicable utility purveyors. Alignment for roadways across the street shall be provided.
F.
Reserve strips prohibited. Reserve strips prohibiting access to streets or adjoining property shall not be permitted except where, in the opinion of the Planning Board, such strips shall be in the public interest.
G.
Street intersection design. Street intersections shall be laid out either directly opposite one another, or be separated by a minimum offset of 200 feet from center line to center line, unless otherwise specified by the Planning Board. Streets shall be laid out to intersect as nearly as possible at right angles. No street shall intersect any other street at less than 60°. Street intersections on the same side of the roadway shall be separated by a minimum of 350 feet from center line to center line.
H.
Driveway intersections. The center line of new subdivision way intersections shall be separated from all existing and proposed driveways (both within and outside of the subdivision) by a minimum of 75 feet.
I.
Curb radius. Street right-of-way lines at intersections shall have a minimum curb radius of not less than 30 feet. Where the angle of intersection between two streets varies more than 10° from a right angle, the radius of the curve at the gutter line curblines at the obtuse angle shall be less and at the acute angle shall be correspondingly greater than the radius specified herein to the extent approved by the Planning Board.
J.
Minimum center line radii. The minimum center line radii of curved streets shall be 150 to 200 feet for residential streets, and 500 feet for commercial streets. All curved streets shall be designed to ensure safe vehicular travel.
K.
Minimum length of tangent between reverse curves. The minimum length of the tangent between reverse curves shall not be less than 150 feet.
L.
Minimum center line grade. The center line grade of any street shall not be less than 1%.
M.
Maximum center line grade. The maximum center line grade shall not exceed 5%.
N.
Vertical curves. All changes in grade exceeding 0.5% shall be connected by vertical curves of sufficient length to afford a suitable sight distance. For purpose of design calculations a minimum K value of 30 on a crest curve and 35 on a sag curve shall be provided.
O.
Leveling area and maximum gradient at intersections. A profile shall be provided for a distance of 200 feet on each side of layout lines. Where the gradient of any street is 5% or greater within 150 feet of the intersection of street right-of-way lines, a leveling area of at least 75 feet with a maximum gradient of 3% shall be provided. No street shall intersect another street at a gradient in excess of 3%.
P.
Maximum gradient on dead-ends. No center line gradient shall exceed 5% within 500 feet of a dead end.
Q.
Retaining walls, guard fences and slopes. Whenever the approved street grade differs substantially from the grade of adjacent land, or where otherwise determined by the Planning Board to be reasonably necessary for public safety, the applicant shall be required to erect retaining walls and guard rail fences or provide slopes with proper plantings to retain the slope, not steeper than 3:1. The Planning Board shall approve the type and dimensions of such retaining walls, fences or slopes and all work shall conform to the "Standard Specifications" of the Town of Salisbury. Construction of retaining walls shall conform to the standards established by the Massachusetts Highway Department. No work shall be performed in any public right of way other than to tie the pavement of a new subdivision way into the public way at grade level without obtaining the necessary easement interest to do so from Town Meeting. No work shall be performed in any private right of way other than to tie the pavement of a new subdivision way into the private way at grade level without providing evidence of the legal right to do so.
R.
Shoulders. Improved shoulders shall slope toward the paved surface at 1 1/2% slope. They shall be covered with six inches of loam and shall be raked, seeded and rolled and watered. Deviation from the above shall occur only with the written approval of the Planning Board. Improved shoulders on all roads shall be a minimum of four feet wide. In the event that the sidewalk requirement is waived, the improved shoulder shall be a minimum of five feet in width.
S.
Curbs/berms.
(1)
Curbing may be required throughout the subdivision. Granite curbing shall be installed at such points as required by the Planning Board. Vertical granite curbing shall be required at all street corners along the circumference of the roadway for the full length of the rounded curve plus a straight section at each end of the curve for at least six feet in length. Vertical granite curbing may also be required on both sides of streets where the grade exceeds 3%. Additional areas may require vertical granite curbing if, in the opinion of the Planning Board, it would contribute to the proper control of drainage, traffic or pedestrian safety. Driveway cuts shall be at least 10 feet wide and have a curb return at the roadway of three feet in radius. Vertical granite curbing shall be installed at the edge of the pavement wherever the street sideline is laid out on a curve of 60 feet or less radius and at all drain catch basin inlets as specified in Appendix II. Sloped granite curbing may be allowed only with approval of the Department of Public Works.
(2)
Granite curbing shall be cut to the following dimensions: minimum length: six feet; width at top: six inches; depth: 17 to 19 inches; minimum width at bottom: four inches; projection above pavement: six inches. All curbing shall be set in concrete and installed as per Department of Public Works requirements.
T.
Way lines parallel. Way lines shall be parallel.
U.
Free flow of traffic. At principal intersections, extra space shall be required to allow for traffic circles and other devices to expedite the free flow of traffic and to provide for adequate sight distance at the proposed curb cut.
V.
Traffic standard. New development shall be permitted only when the projected traffic that would be generated by the proposed development can be accommodated either by existing roadway capacity or proposed improvements that will ensure public safety.
W.
Extension of streets. Subdivision streets shall be laid out so as to safely connect to existing ways. No subdivision shall be approved unless the proposed streets connect to and are accessible from a public way or a private way that is open and dedicated to public use, having in the opinion of the Planning Board adequate construction, lines, width and grades.
X.
Intersection sight distance. Adequate sight distance shall be provided at all intersections with existing and proposed roadways and as set forth as follows:
(1)
Required stopping distance. The required stopping sight distance shall be calculated under the Stopping Sight Distance of the American Association of State Highway and Transportation Officials, "A Policy On Geometric Design of Highways and Streets 2001," most recent edition, based on the 85th-percentile speed of the major roadway. The 85th percentile speed shall be determined from an acceptable engineering speed study with a minimum of 20 speed observations in each direction.
(2)
Calculation of sight distance. Available intersection sight distance shall be measured a minimum of 15 feet from the edge of pavement along the center line of the proposed roadway. For all calculations, the height of the driver's eye shall be considered to be 3.5 feet above the road surface and the height of the object shall be considered to be 2.0 feet above the road surface in accordance with the most recent AASHTO policy. If this policy is changed after the date of this document the developer shall conform with the policy that is the most safe.
(3)
Required plan details to allow sight distance evaluation. The definitive plan shall detail existing trees (of a caliper greater than six inches), stone walls, fences, topography, driveways and streets within 350 feet and pavement limits so as to allow the Planning Board's technical consultant to adequately evaluate intersection sight distance. The definitive plan shall include the measured sight distance triangles and any applicable approach grades. Sufficient sight easements shall be provided before a plan is approved.