§ 3. ROADWAY DESIGN AND PAVEMENT  


Latest version.
  • The following table contains the specified construction sheets that applicant design must conform to; sheets are available digitally on the City web page and by request:

    Roadway Element Details to use within ROW
    Residential Driveway FC 304 & FC 308, or GDOT A1
    Non-residential Driveway GDOT A1
    Auxiliary Lanes FC 309,310,311
    Pavement Design FC 301* & FC 302*
    Pavement Patch GDOT 1401
    Pavement Widening Less than 5 ft GDOT Class B Concrete; GDOT
    Specs Section 500
    Pavement Installation GDOT Specifications
    Cul-de-sac FC 303
    Bike Lanes GDOT T16, T16a , MUTCD, NACTO
    Curb & Gutter GDOT 9032B or 9032C
    Rolled Curb & Gutter FC 307
    Sidewalks & Multiuse Trails FC 308*
    ADA Ramps GDOT A3* & A4*
    Signing Refer to MUTCD
    Crosswalk Striping GDOT T11a
    Pavement Markings - Words GDOT T13a, T13b, T13c
    Pavement Markings - Arrows GDOT T12b
    Raised Pavement Marking GDOT T15a & GDOT T15c
    Retaining Wall
    (Need approval from Director)
    GDOT 9031L & GDOT PW-1
    Drainage Structures GDOT 1033D & GDOT 1034D
    Ped Lighting COSS Details

     

    *as modified with the Development Code, latest edition.

    A.

    General requirements.

    1.

    The sections enumerated in this article are guidelines, and are intended to be benchmark indicators of what standards could be acceptable. They are further intended to allow alternate designs which could produce results similar to these performance standards and similar protection to the public. The objective of these performance standards is not to suggest a single methodological standard of acceptance exclusive of all others. Rather they establish what would otherwise be allowed in the absence of an acceptable alternative.

    2.

    All new streets proposed to be constructed in a subdivision or other development, whether to be public or private, shall be designed and constructed to the standards contained in this section and in accordance with the classification of said street.

    3.

    Streets, whether existing or new, shall be constructed or improved under those circumstances and to the standards as established in this section. Roadway improvements shall be in accordance with the street framework type classifications as shown in the Street Framework Map of the City of Sandy Springs, Development Code, or as otherwise required by the Director.

    Specifications.

    Unless otherwise specifically set forth herein, all of the materials, methods of construction, and workmanship for the work covered in reference to street construction shall conform to the latest specifications of GDOT, Fulton County, and the City of Sandy Springs.

    B.

    Driveway intersections and access improvements.

    1.

    Angle and improvements. Driveways shall generally be at right angles and shall not be at an angle of less than 85 degrees for roadways classified as arterial or collectors and 80 degrees for all other roadway classifications unless approved by the Director. This requirement may be waived by the Director where the driveway access is to a substandard road (i.e. dirt or gravel) or a rural road section. Driveways providing access to parking lots which contain six or more spaces shall be paved in accordance with the parking lot requirements of the Development Code, latest edition.

    2.

    Driveway design standards.

    a.

    Driveways provide access to property and are a service to the traveling public. However, vehicles entering or leaving driveways may disrupt the flow of traffic on streets and cause accidents, thereby infringing on the rights of the public to travel the roadway. All driveways should be restricted to locations where movements into and out of them can occur in a safe and orderly manner.

    b.

    Because of their simple appearance, driveways often do not receive sufficient design consideration. At the least, driveways should always be designed to eliminate or minimize opposite lane encroachment while entering and exiting property.

    c.

    All driveways are to be designed and constructed with sidewalk transitions as appropriate. Cross slope shall not exceed two percent in area where sidewalk is present or is planned to be installed according to an approved sidewalk master plan, City of Sandy Springs, Georgia, Comprehensive Plan or project approved by mayor and city council.

    d.

    All driveways are to be considered low volume intersections and to comply with minimum intersection/corner sight distance requirements of this section.

    e.

    All driveways shall slope up from the edge of road a minimum of six inches within the right-of-way to ensure that stormwater surface flow is maintained within the right-of-way. This requirement may be waived by the Director in road sections that drain away from the gutter line, i.e. the high side of super-elevated curves.

    f.

    No catch basins will be allowed within access/driveway radii (turning radii).

    g.

    Where a driveway is constructed at a location that has or should have a ditch along the roadside for the purpose of collecting, channeling, and controlling stormwater runoff the driveway shall be constructed with a culvert designed to conduct stormwater beneath the driveway in accordance with the following:

    i.

    Concrete or other type of culvert approved by Community Development Department;

    ii.

    Sized to accommodate the 25-year storm, as a minimum, with a minimum pipe size of 24 inches. Larger storm events may be required as specified in Section 10;

    iii.

    Provided with flared-end sections or headwalls at the inlet and outlet;

    iv.

    Of sufficient length to accommodate a minimum of two-foot shoulders at each end of the driveway with a maximum side slope of 2:1 to the bottom of the ditch line; and,

    v.

    Installed in a ditch of minimum two-foot wide flat bottom with sides sloped at a grade no greater than 2:1 stabilized with acceptable vegetation.

    3.

    Residential driveway standards. Residential driveways provide a primary means of access to single-family, detached residential uses and shall conform to the following:

    a.

    Width: Minimum 12 feet, maximum 16 feet within the right-of-way, as measured from edge of pavement.

    b.

    Radii or flare: Minimum five feet.

    c.

    The curb cut shall not encroach on the radius of the curb at a street corner.

    d.

    In no case shall the edge of the curb cut be less than five feet from the side property line, as measured along the right-of-way.

    e.

    Length: A minimum of 25 feet or to the edge of the city or state right-of-way, whichever is greater, shall be paved with a treated hardened surface. Rural residential driveways may be constructed with an asphalt pavement section, if approved by the department. This requirement may be waived by the Director where the driveway access is to a substandard road (i.e. dirt or gravel) or a rural road section.

    f.

    Not more than two curb cuts shall be permitted on any one street frontage classified as a local street. When two cuts are permitted there shall be a safety zone of not less than 25 feet, as measured along the curb line, between the inside edges of the driveways.

    g.

    Not more than one private curb cut may be located on any one street frontage for any one dwelling where the street is classified as a collector or higher order street. If a lot has access to more than one frontage, it may not have any private curb cuts on a street that is classified as a collector or higher order street. If both frontages are classified as collector or higher order streets, then the curb cut may be on the frontage with the lowest classification, or as designated by the department.

    h.

    Multiple lot (subdivision) development: For developments of two or more adjoining lots, driveways shall be located outside of building setbacks and zoning buffers on all lots abutting the exterior of the project site. For lots interior to the project site (not adjacent to exterior lot lines, setbacks or zoning buffers), driveways may be located within side setbacks.

    i.

    Lots previously developed as single family detached homes: Driveway locations may remain in the existing location as was previously used to access the property (regardless of zoning class);

    j.

    Lots with a front building setback width of less than 130 feet: Driveway can be located anywhere within the confines of the property, provided that each lot has only one curb cut per public street; or

    k.

    Lots with front building setback width equal to or greater than 130 feet: If redeveloped lot driveway may either be located in the previously used location or driveway must be located at least ten feet from side property line. Vacant lots not previously developed as a part of a platted residential subdivision: driveway must be located at least ten feet from the side property line.

    4.

    Nonresidential driveway standards. Nonresidential driveways (other than single-family detached uses) shall provide uninterrupted ingress/egress to and from the site and shall conform to the following standards:

    a.

    The minimum distance required is measured perpendicular from the street right-of-way line at the ingress/egress point to the nearest edge of any interior service drive or parking space with direct access to such. The length of the uninterrupted ingress/egress is determined by the maximum peak hour volume of the facility in which the driveway is provided and as shown in the table below. The developer shall provide this information.

    Table 3-1. Uninterrupted Ingress/Egress Distances

    Maximum peak hour volume
    Uninterrupted
    ingress/egress (feet)
    Up to 50 vehicles 25
    50 to 200 vehicles 50
    201 vehicles and up 100

     

    b.

    Nonresidential driveways shall not be designed or marked to allow more than one lane of traffic to exit onto a street simultaneously, unless such driveway is channelized in accordance with traffic engineering design principles as applicable when designing channelized street intersections.

    c.

    Width (measured from edge of pavement to edge of pavement):

    Table 3-2. Nonresidential Driveway Width

    Entrance configuration Minimum width (feet) Maximum width (feet)
    One-way 12 18
    Two-way 22 33

     

    Notes:

      Where no other access is provided a minimum width of 20 feet shall be required.

      Additional width may be approved by the Director based on an approved engineering design.

    d.

    Entrance radii shall be based on the road classification at the proposed entrance location and shall conform to the requirements set forth in this section.

    e.

    Composition: Within the right-of-way the driveway and access improvements shall meet or exceed the same specification as the connecting public roadway.

    f.

    Drainage: Consistent with existing drainage plan of the connecting public roadway unless other improvements are required for safety, hydrological and environmental considerations.

    g.

    Driveway designs other than as provided within this chapter, i.e., median divided or additional lanes, are subject to consideration of the community development director.

    5.

    Access limitations for development adjacent to thoroughfares.

    a.

    All access points and driveways adjacent to thoroughfares may be subject to further restriction and consideration as may be deemed necessary by the GDOT and/or the city to ensure safe, functional design and efficient operation of the thoroughfares.

    b.

    Access to all residential lots shall be from interior subdivision streets or roads where possible. Exceptions are subject to approval from the Director. Subdivisions of three or less lots may be exempted upon approval by the Director with proper consideration of safety, hydrological, and environmental concerns.

    c.

    If the closest intersection is or is likely to be signalized, traffic movements to and from any driveway within 250 feet of an intersection with (as measured from the point of tangency) a collector or an arterial shall be limited to right turns only.

    6.

    Median openings.

    a.

    No median opening shall be spaced at a distance less than 660 feet for urban roadways or 1,320 feet for rural roads from any other median opening (measured from centerline to centerline) unless specifically approved by the Community Development Director.

    b.

    Other factors will also be considered, such as distance to other median openings, adjacent land use, expected traffic volumes, and the resulting volume of U-turns that are likely to occur without the median opening. Meeting the spacing criteria is not, in itself, an indication that median openings will be allowed.

    c.

    All median openings shall include full width storage and taper length in accordance with Tables 3-6 and 3-7 unless otherwise acceptable to community development director based on a traffic study. Increased storage and transition lengths may be required to eliminate disruption of through-traffic flow. Provide a minimum 11-foot pavement width, excluding curb and gutter.

    7.

    Spacing of signalized intersections. No signalized intersection shall be spaced at a distance less than 1,000 feet for urban roadways or 1,320 feet for rural roads from any other signalized intersection (measured from centerline to centerline) unless specifically approved by the Community Development Director.

    8.

    Auxiliary lanes (turn lanes and deceleration lanes).

    a.

    Improvements required.

    i.

    When property that abuts upon an existing or proposed city road is to be developed or redeveloped and the city road will provide access to the property, access improvements to the city road (deceleration lanes, turn lanes, etc.) shall be provided by the developer.

    ii.

    When any auxiliary turn lane that extends beyond the applicant property frontage, the applicant will be responsible for acquiring the necessary rights-of-way and easements in order to accomplish the necessary frontage improvements.

    b.

    Deceleration lane. A deceleration lane shall be constructed at no cost to the city at each project driveway or subdivision street entrance, as applicable, that meets either the average daily traffic (ADT) or right turning volumes shown in the following table. Passing lane sections fall under the criteria for two or more lanes. The Director may require the construction of a deceleration lane even when the conditions in Table 3-3 are not met, if roadway or field conditions indicate that the safety of the general public would be improved.

    Table 3-3. Minimum Volumes Requiring Deceleration Lanes

    2 Lanes on Main Road >2 Lanes on Main Road
    35—40 mph >40 mph 35—40 mph >40 mph
    Main Roadway ADT 8,000 4,000 12,000 10,000
    Daily Right Turning Volume 150 75 150 75
    Peak Hour Right Turning
    Volume
    15 7 15 7

     

    Deceleration lanes required by this section shall meet the following requirements:

    i.

    Deceleration lanes shall have a pavement width of 12 feet (exclusive of curb and gutter) and shall meet the following standards for storage and taper length:

    Table 3-4. Deceleration Lane Storage and Taper Lengths

    Posted Speed Limit (mph) Full Width Storage (ft) Taper (ft)
    35 100 50
    40 150 50
    45 175 100
    50 225 100

     

    ii.

    Additional right-of-way to accommodate the deceleration lane and an 11-foot shoulder shall be dedicated by the developer to the city at no cost. Associated drainage improvements as deemed necessary by the construction of the deceleration lane shall also be required.

    iii.

    Other access improvements may be required by the Community Development Director in order to ensure adequate site access, pedestrian access, convenience and safety to the motoring public.

    iv.

    The pavement specifications for deceleration lanes must comply with the GDOT standard specifications of roads and bridges, except as approved by the Community Development Director.

    c.

    (3) Medians. In the event a street has an existing or proposed median, the opening will be reviewed in accordance with GDOT standards, latest edition.

    d.

    (4) Left turn lanes. Left turn lanes must be constructed at no cost to the city if either the ADT or left turning volumes shown in the following table are met. Passing lane sections fall under the criteria for two or more lanes. The Community Development Director may also require the addition of a right turn lane, even when the conditions in the following table are not met, if roadway geometry or field conditions indicate that the safety of the traveling public would be improved.

    Table 3-5. Minimum Volumes Requiring Left Turn Lanes

    2 Lanes on Main Road >2 Lanes on Main Road
    35—40 mph >40 mph 35—40 mph >40 mph
    Main Roadway ADT 6,000 4,000 10,000 8,000
    Daily Left Turning Volume 300 200 300 200
    Peak Hour Left Turning Volume 30 20 30 20

     

    Left turn lanes required by this section shall meet the following requirements:

    a.

    The design of left turn lanes should consider the intended function and the characteristics of the roadway. In many cases, it is necessary to widen the existing roadway to introduce the left turn lane. Left turn lanes shall be constructed at no cost to the city.

    b.

    When the roadway has a median that is at least 20 feet wide, the left turn lane can be developed out of the median, avoiding the need for transitions. If a proposed driveway aligns across the main street with another driveway, and the proposed driveway must provide a left turn lane and left turn storage, then adequate storage and tapers must also be provided for the driveway across the main street.

    c.

    The basic design elements of left turn lanes are illustrated in the following table. This example shows symmetrical widening, which basically requires the through traffic on each side to shift by one-half of the lane width. Some circumstances may dictate that all widening be achieved on one side, which requires a full lane shift for through traffic on the side where the additional width is developed.

    fIG3-1.png

    Figure 3.1: Design Elements of Left Turn Lanes

    Table 3-6. Minimum Design Elements of Left Turn Lanes

    SPEED LIMIT (MPH) APPROACH TAPER (FT) BAY TAPER
    (FT)
    FULL WIDTH STORAGE (FT)
    6' SHIFT 12' SHIFT
    35 125 180 50 See Table 11.4-8
    40 160 250 50 See Table 11.4-8
    45 270 320 100 See Table 11.4-8
    50 300 540 100 See Table 11.4-8
    55 330 600 100 See Table 11.4-8

     

    d.

    The required length of full-width storage is based on the peak hour traffic volumes. This should be determined in the traffic study. The amount of storage is dependent on the type of traffic control in effect. For signalized intersections, the storage should be sufficient to accommodate the 95th percentile peak hour queue. At yield-controlled intersections, the storage is based on the number of vehicles as designated in Table 3-7.

    Table 3-7. Left Turn Storage Requirements

    PEAK HOUR LEFT TURN VOLUME EQUIVALENT NEIGHBORHOOD SIZE
    (# OF LOTS)
    SPEED LIMIT OF ROAD
    35 MPH 40 MPH 45 MPH 55 MPH
    QUEUE FEET QUEUE FEET QUEUE FEET QUEUE FEET
    30 to 36 80 to 104 95 95 95 95
    37 to 84 105 to 268 115 115 115 115
    85 to 100 269 to 325 135 135 135 135
    101 to 125 326 to 417 135 135 155 175
    126 to 150 418 to 511 155 155 175 190
    151 to 175 512 to 607 175 175 190 210
    176 to 200 608 to 704 190 190 210 210

     

    9.

    Relocation of utilities. The developer shall be responsible for the relocation of public or private utilities and drainage structures as may be occasioned by the required project access improvements.

    10.

    Left turning control radii. The path of the inside wheels during left turns is important for the design of median openings and intersections with dual left turn lanes. The following radii shall be used for the design of entrance improvements.

    fIG3-2.png

    Figure 3.2: Left Turning Control Radius

    Table 3-8. Left Turning Control Radius

    DRIVEWAY USE CONTROL RADIUS (FT)
    Residential 40
    Commercial 50

     

    11.

    Corner sight distance. All driveways shall provide adequate corner sight distance in accordance with the standards established for an intersection as set forth in this section.

    12.

    Separation and spacing. All driveways except those serving residential units on individual lots shall be recommended to meet the following criteria:

    a.

    Spacing requirements, associated with the construction of new driveways, are provided in the following Table 3-9. Driveways should be separated from any other facility, which accesses a city roadway, whether it is another driveway or a public street. Minimum spacing requirements also apply to driveways on the opposite side of undivided roadways.

    fIG3-3.png

    Figure 3.3: Spacing Criteria for Driveways

    Table 3-9. Driveway Spacing Criteria

    POSTED Speed (MPH) MINIMUM DRIVEWAY SPACING (FT) (1)
    25 200
    30 250
    35 300
    40 300
    45 300

     

    Notes:

    (1) Requirements for the length of right and left turn lanes, as shown in Table 3-4 and Table 3-6, may increase the minimum allowable spacing shown in Table 3-9.

    b.

    Spacing of one-way driveways. Figure 3.4 shows a typical layout of one-way driveways. The spacing criteria presented in Table 3-10 does not apply to the distance between the two one-way driveways (driveway pair). A driveway pair must be separated from another driveway pair by the distance as shown in Table 3-10. A driveway pair must also be separated from an adjacent two-way driveway in accordance with the spacing criteria in Table 3-10.

    fIG3-4.png

    Figure 3.4: Spacing Criteria for One-Way Driveways

    c.

    Placement of driveways. Not only must driveways be spaced from other driveways as provided above, they must also be located a minimum distance from the property line. The radius return must be a minimum of five feet from the property line.

    When driveways are to be jointly used by two or more property owners, the property line separation requirements given in the above paragraph can be waived. However, a joint use agreement signed by the affected property owners must be provided to the community development director. Either property owner may apply for the driveway permit.

    d.

    Driveway spacing. Driveways should align with other driveways located on the opposite side of the roadway. If offset driveways cannot be avoided, the same driveway spacing criteria as given in Table 3-9 should be provided, to provide space for left turns. Figure 3.5 shows how the spacing is measured for locating offset driveways on undivided roadways. Spacing is from center to center.

    fIG3-5.png

    Figure 3.5: Spacing of Offset Driveways

    If the city roadway involved is a divided facility and the driveways do not align with a median crossover, the driveway spacing would only apply to the adjacent driveway located on the same side of the roadway as shown above in Figure 3.5.

    e.

    Maximum number of driveways serving a single project: One for each full 200 feet of property frontage. This is not meant to be a spacing standard but only an expression of the maximum number of driveways that are permitted serving a single project.

    13.

    Raised islands. Raised islands associated with entrance improvements shall be designed in accordance with the standards provided herein.

    14.

    Right-in, right-out driveways.

    a.

    Raised islands are also typically used to channelize the movements at a driveway where only right turns are allowed. The raised island is an effective means of preventing left turns. All right-in, right-out islands must have a radius that is 70 feet, or a compound curve that approximates 70 feet.

    b.

    Right-in, right-out driveways are not intended for truck traffic, so the exit and entrance lanes must be 12 feet in width as measured from face of curb to face of curb. The island must be constructed from mountable curb (three inches vertical, 45-degree face, three inches flat) to accommodate emergency vehicles. The edge of the island should be offset 18 inches to 24 inches from the edge of the travel lane.

    15.

    Pavement design.

    a.

    All construction, within the right-of-way, of surfaces intended for travel by motorized vehicles shall be paved. The pavement specification of auxiliary lanes on city roadways shall be the GDOT Standard Specifications for Construction of Roads and Bridges, or as designated in city standards, whichever is more restrictive.

    b.

    New developments are required to widen the road along their frontage to a uniform lane width of 11 feet. If the widened area is two feet or less in width, a concrete sub-base should be provided per the current standards. The developer must then either pave the entire width of the road, or mill to the centerline and pave to match the existing road. Transitions shall be milled a minimum of 25 feet. Any deviation from this standard requires a waiver from the Director.

    16.

    Pedestrian considerations. When driveways are constructed in areas where pedestrian activity is not prohibited, the design should adequately provide for pedestrian movement and interaction with vehicular traffic. Pedestrian features that should be considered include sidewalks, crosswalks, traffic control features, and curb ramps are required. The Americans with Disabilities Act Accessibility Guidelines must be utilized where pedestrian traffic is expected.

    C.

    General layout requirements.

    1.

    Conformance. The arrangement, character, extent, width, grade, and location of all streets shall conform at a minimum to the comprehensive plan and this chapter.

    2.

    Local streets and collectors. Local streets shall be laid out so that their use by through traffic will be discouraged. Collectors shall be provided to channel through traffic movements within a development, where appropriate to the design and a major thoroughfare is not proposed by the comprehensive plan. Collectors also may be provided as central routes within large residential subdivisions, where appropriate to the design, based on project traffic demands exceeding 4,000 trips per day (ADT).

    3.

    Cul-de-sac streets.

    a.

    Maximum length without an approved turnaround. Dead-end streets more than 150 feet in length, as measured from the centerline of the intersecting street to the end of the improved access road, shall provide a cul-de-sac turnaround. Alternative turnarounds may be provided as approved by the fire marshal and the Director.

    b.

    Minimum street length. The minimum street length for a cul-de-sac street shall be 50 feet.

    c.

    Maximum design length. Cul-de-sac streets may be no more than 600 feet in length. Additional length necessitated by topography or property configuration may be approved by the Director.

    d.

    Measurement of cul-de-sac length. The length of a cul-de-sac street shall be measured along the centerline from the point of tangency of the entrance radius to the point of curvature for the cul-de-sac radius return.

    e.

    Eyebrow cul-de-sac. Eyebrow cul-de-sac (half cul-de-sac) will be allowed only at "right-angled" intersections having an interior angle between 80 degrees and 100 degrees.

    f.

    Conformance to standard drawings. Cul-de-sac shall conform to the layout and dimensional requirements as shown in the standard drawings.

    g.

    Cul-de-sac with landscape islands. Nonstandard cul-de-sacs will be evaluated individually and may be constructed with a landscaped island (subject to approval by the fire marshal and the Director) to be maintained by the homeowners' association in perpetuity.

    h.

    Minimum cul-de-sac radius. Minimum cul-de-sac radii shall be 50 feet.

    4.

    Other dead-end streets.

    a.

    A dead-end street shall be provided to the boundary of a subdivision where necessary to provide access to a land-locked abutting property, for planned continuity of future circulation, for improved access for public safety vehicles, or for the extension of public water or other utilities to neighboring lands. Such dead-end streets shall be designed so as to allow their reasonable extension, and shall be located so as to be reasonably incorporated into a street design for the neighboring property. The stub street requirement may be waived by the Director, provided the fire marshal concurs.

    b.

    In residential subdivisions, a dead-end ("stub") street required, under this section, to provide access to an abutting property may be exempted from construction of roadway improvements and public utilities under the following circumstances:

    i.

    No lot within the proposed subdivision will gain access from the "stub" street; and,

    ii.

    A concept plan has not been submitted or approved on the neighboring tract; and,

    iii.

    The "stub" street shall be fully designed as part of the development plans. However, the right-of-way shall only be cleared and rough graded in accordance with the approved plans, and all disturbed areas grassed; and,

    iv.

    Connections for future extension of all public utilities shall be constructed as part of the subdivision. Curb returns shall be constructed as part of the subdivision. Curb returns shall be provided to the future "stub" street roadway location, and curb and gutter shall be installed across the roadway stub at the right-of-way line (extended); and

    v.

    The right-of-way for the "stub" street shall be dedicated as part of the final plat. Slope easements or construction easements, if required by the street design, shall be shown on the final plat.

    c.

    Dead-end streets on abutting property shall be extended into a proposed subdivision and incorporated into the street design of the development. This requirement may be modified by the director in cases of serious topographical hardship or dissimilar zoning which would create unacceptable land use conflicts between the two developments. This modification may be conditioned on the provision of easements necessary for the extension of public utilities, the provision of cul-de-sac or other permanent turnaround on the dead-end street, or the removal of the dead-end street back to its nearest intersection.

    d.

    Where a dead-end street (other than a cul-de-sac) serves more than three lots, the developer shall be required to provide a temporary vehicular turnaround within the right-of-way. This requirement may be waived if extension of the dead-end street is approved and under construction prior to its inclusion in a final plat.

    e.

    (5) Where a street dead-ends at the property boundary and the street exceeds the maximum cul-de-sac length a permanent cul-de-sac shall be required. In this situation, right-of-way to the property boundary shall be required, but the pavement shall not be extended to the property boundary beyond the edge of the paved cul-de-sac turnaround.

    5.

    Service roads.

    a.

    Where a development borders on or contains a railroad right-of-way, or limited access highway right-of-way or major thoroughfare, a public street may be required to be constructed and dedicated within the development approximately parallel to and on each side of such right-of-way.

    b.

    All driveways along designated thoroughfares with existing or planned service roads shall provide access to such service roads. To gain temporary direct access to the thoroughfare, the developer shall construct the section of the service road adjacent to the development. The service road section shall be located where planned. Any right-of-way not previously dedicated shall be dedicated prior to consideration of a temporary driveway approval providing direct access to the thoroughfare.

    6.

    Half-streets. Half-streets (new boundary streets having one-half of the minimum required right-of-way or pavement width) shall not be allowed nor access to same be permitted should it exist.

    7.

    Reserve strips. Land in private ownership adjacent to public rights-of-way which could control or are intended to control access to streets, alleys, or public lands shall not be permitted unless their control is given to the city under ownership, dedication, or easement conditions approved by the city attorney or acceptable to the Director. No development shall be designed so as to deny access to abutting properties.

    8.

    Alleys. Alleys shall not be provided except where the developer produces evidence satisfactory to the Director of the need for same. In the event the Director approves a design which proposes alleys, the alley shall be constructed as though it were a local street pursuant to the standards contained in this chapter.

    9.

    Street jogs. Streets shall be aligned as per driveways as shown on Table 3-9.

    10.

    Traffic calming. Where residential streets are longer than 600 feet, traffic calming devices may be incorporated as required by the Director. The design of all measures shall comply with the applicable standards for the construction of such measures.

    11.

    Bike infrastructure. When required, the developer shall dedicate sufficient right-of-way to the city, or applicable entity, and install the necessary pavement and other improvements for the construction of bicycle infrastructure in locations as may be required by the Director or Road Cross-section Standards. Bicycle lanes shall be a minimum of five feet in width as measured from the edge of pavement, not including curb and gutter, and constructed in accordance with the AASHTO Guide for the Development of Bicycle Facilities, latest edition, the Manual of Uniform Traffic Control Devices for Streets and Highways, latest edition, and the NACTO Urban Bikeway Design Guide, latest edition.

    12.

    Bus shelters. When required, the developer shall provide bus shelters within or adjacent to the right-of-way which are in compliance with the design standards of the local transit authority and as approved by the city. The Director may require the construction of turnout areas or widened shoulders to accommodate the loading and unloading of passengers.

    D.

    Minimum right-of-way and street improvements.

    1.

    Right-of-way and pavement widths.

    a.

    Minimum rights-of-way for new street construction shall be as required by the Cross Section Standards database or per the City of Sandy Springs Right-of-Way Plan unless otherwise approved by the Director.

    b.

    Additional street right-of-way width may be required to be dedicated at intersections or other locations fronting the property where turning lanes, storage lanes, medians, realignments, sidewalks, utilities or other necessary improvements are required and minimum right-of-way standards would be inadequate to accommodate the improvements.

    c.

    A minimum of ten-foot travel lanes are required on all streets, except for alleys where the principal structure may also be served by a higher classification street. Roadway widths and lane assignments are typically based upon the functional classification of said roadway, but in no case shall those widths be less eleven (11) feet, unless otherwise approved by the Director. Lane widths exclude curb and gutter.

    d.

    Median divided roadways may be required with left turn bays and median breaks in lieu of center two-way left turn lanes.

    e.

    Existing streets shall be continued at the same or greater width, but in no case shall it be less than the required width provided herein. Where street widths change an appropriate transition shall be provided as approved by the Director.

    2.

    Street rights-of-way.

    a.

    Dedication of street right-of-way. Right-of-way for all public streets, existing and proposed, shall be dedicated in accordance with the street classifications as shown on the long-range road classification map of the comprehensive plan and in accordance with this chapter. Right-of-way dedications shall be made prior to the approval of a final plat or, where a final plat is not involved, prior to the issuance of a land disturbance permit, unless otherwise approved by the Director.

    b.

    Right-of-way for projects adjacent to comprehensive plan projects. If a new street or thoroughfare is proposed by the city transportation or comprehensive plans or the State of Georgia to adjoin or traverse the property, permits shall not be issued until the department has submitted the project to the mayor and city council for review in order to seek a determination if the city should acquire the right-of-way or if a study of alternate routes should be undertaken. The review period by the city shall not exceed 90 days from the date of permit application. If, after the 90-day review, the mayor and city council is unable to reach a decision, there shall not be any further delay of a requested permit for this situation.

    c.

    Right-of-way for projects adjacent to funded roadway projects. If a new street or thoroughfare is funded by the city or the State of Georgia to adjoin or traverse the property, the proposed road right-of-way shall be incorporated into the development plans of the property in accordance with this chapter. The right-of-way requirements contained in this chapter shall govern except where there exists clearly defined plans of GDOT or the city, which require additional right-of-way. In that case, the greater right-of-way requirements shall govern.

    d.

    Right-of-way for projects adjacent to designed roadway projects. Any development with property fronting on an existing city road for which there exists clearly defined plans by GDOT or the city, may be required to provide road improvements associated with the defined plans or, in lieu of the design and construction, at the discretion of the mayor and city council, the developer may be required escrow the dollar equivalency of required improvements (including curbing, utility relocation, and drainage structures), as estimated by the developer and verified by the community development director. These funds shall be deposited in the appropriate road construction account prior to the approval of development improvements or within 30 days of city award of a construction contract, whichever occurs first.

    e.

    Dedication of minimum required right-of-way for abutting streets. On any existing street that abuts a property and does not meet the right-of-way requirements as established in this chapter, one-half of the required width of right-of-way shall be dedicated to the city as measured from the centerline of the roadway prior to the issuance of a land disturbance permit for that property.

    f.

    Location of the right-of-way. Except where it can be shown to be in the best interest of the safety, health and welfare of the general public or specifically approved by the community development director the location of the right-of-way shall be located as follows:

    i.

    The right-of-way shall be parallel the back of curb or be mitered at intersections to provide adequate area for utilities, sidewalk, sight distance and maintenance of the right-of-way.

    ii.

    Right-of-way shall be located a minimum of 11 feet from the back of curb or one foot from the back of sidewalk, whichever is greater, to prevent interference or encroachment by fencing, walls, hedges and other planting or structures that may be placed on the adjacent property line at a later date.

    g.

    Right-of-way setback adjacent to residentially zoned property. The right-of-way for new public streets or the easement/common area for new private streets must be located a minimum of 50 feet from any peripheral property line adjoining residentially zoned property unless inter-parcel access is required. This setback shall comply with the provisions of section for "reserve strips".

    h.

    Minimum right-of-way miters. When right-of-way miters are required at intersections to provide area for adequate utility location and maintenance, the miters shall comply with the following minimum standards, the miter distances shall be measured along the right-of-way from the point of intersection of the two rights-of-way if they were extended:

    i.

    Twenty-foot miters (minimum) shall be provided at the right-of-way intersection of any major thoroughfare.

    ii.

    Ten-foot miters (minimum) shall be provided at the right-of-way intersection of any local roads.

    iii.

    Intersecting right-of-way lines may be joined by an arc having the minimum radius shown, or by a miter which cuts across the right-of-way lines connecting the points where the required radius would have otherwise been tangent.).

    3.

    Substandard streets.

    a.

    Ingress/egress. All subdivisions and developments shall provide at least one means of ingress/egress from an improved road as determined by the Director. This condition may be waived in areas where the size of the lot or other conditions of zoning permit the development of single-family residential units to utilize a substandard street.

    b.

    Substandard street improvements. In the event that a development which is not permitted to access substandard streets through a right or condition of zoning has access to a substandard street (i.e., a dirt or gravel road), the following project access improvements shall be required:

    i.

    If the abutting substandard street provides access to the development and is dirt or gravel, the street shall be upgraded by the developer to a paved roadway from the project entrance to the nearest standard paved road along the route of access.

    ii.

    Off-site project access improvements, shall at a minimum, result in a full-section roadway meeting the requirements of a local residential roadway at minimum. In cases where the internal roadways have been designated as a higher classification the off-site improvements shall be designed to meet the standards of the higher classified road. Responsibilities shall be as follows:

    iii.

    The Developer shall design the road and provide the labor, equipment, and materials required for roadway improvements and necessary drainage and utility improvements. Where a rural road section has been approved the drainage improvements shall include all necessary drainage swales.

    iv.

    All right-of-way required for these off-site improvements shall be acquired by the developer at no expense to the city. If the developer is unable to acquire the right-of-way, the City may initiate acquisition proceedings, at the expense of the developer, after authorization by the mayor and city council.

    4.

    Improvements along state highways. For any development which abuts a state highway or other right-of-way controlled by the State of Georgia, improvements to the roadway and the location and design of any street or driveway providing access from the state highway shall comply with the standards and requirements of GDOT or the City of Sandy Springs, with the more restrictive requirements controlling. The proposed access or improvements shall be required to have been approved and permitted by GDOT and incorporated into the construction drawings for the project prior to issuance of a land disturbance permit by the Department.

    E.

    Roadway design.

    1.

    Street grades and design speeds.

    a.

    Minimum grade. Minimum grade for all local streets shall be 1.5 percent. Minimum grades for all collector and arterial streets shall conform to GDOT practice unless noted otherwise.

    b.

    Minimum grades of less than 1.5 percent on a local street may be approved by the department, based on adequate engineering designs, where at least 1.5 percent cannot reasonably be achieved due to topographical limitations imposed by the land. In such cases, a record drawing and such computations as necessary shall be provided after construction to establish that the street will drain in accordance with this chapter. Street sections where unacceptable pooling, excessive spread at catch basins, or other hazardous conditions occur shall be reconstructed or otherwise improved to eliminate such conditions.

    c.

    Maximum grade and design speed. Minimum vehicle design speeds and maximum grades allowable in the city by street classification shall be as shown in the following table.

    Table 3-10. Minimum Design Speeds and Maximum Grades

    STREET CLASSIFICATION MAXIMUM GRADE (1) MINIMUM DESIGN SPEED (MPH)
    Collector/Arterial 10% 40
    Nonresidential Local 12% (2) 30
    Residential Local 14% (2) 25

     

    Table 3-10 Notes:

    (1) Maximum grade in excess of those listed above may be approved by the Director in order to address topographical safety, hydrological, and environmental concerns.

    (2) Grades between 12 percent and 14 percent shall be limited to a maximum length of 150 feet. The distance shall be measured as the tangent length between points of curvature.

    d.

    Maximum grade for cul-de-sac. Maximum grade on any cul-de-sac turnaround shall be six percent.

    e.

    Roadway cross slope. The standard roadway cross slope is two percent down from crown to gutter line or edge of pavement. In areas where pavement width is being added to an existing street, the additional pavement shall match the cross slope of the existing roadway.

    2.

    Vertical street alignment.

    a.

    Requirements for vertical curves. All changes in street profile grades having algebraic difference greater than one percent shall be connected by a parabolic curve having a minimum length (L) equal to the product of the algebraic difference between the grades in percent (A) and the design constant (K) assigned to the street according to its category (i.e., L=KA).

    b.

    Required K values.

    Table 3-11. Constant (K) Values For Vertical Curves

    STREET CLASSIFICATION CREST CURVES SAG CURVES
    Collector 44 64
    Nonresidential Local 19 37
    Local Residential 12 26

     

    c.

    Minimum vertical curve length. The minimum length of vertical curve required for safe stopping sight distance shall be calculated using AASHTO "Policy on Geometric Design of Highways and Streets", latest edition.

    3.

    Horizontal street alignment.

    a.

    Minimum horizontal curves and superelevation. All new streets shall adhere to the following standards governing horizontal curvature and super elevation:

    Table 3-12. Horizontal Curves

    STREET CLASSIFICATION MINIMUM RADIUS (FT) MAXIMUM
    SUPERELEVATION
    Collector 560 0.04
    Nonresidential Local 150 Normal Crown
    Local 120 Normal Crown

     

    Notes:

    (1) No super elevation will be allowed on collectors internal to residential subdivisions.

    b.

    Calculation of superelevation:

    Superelevation for horizontal curves shall be calculated utilizing the following formula:

    R= v /(15 (e + f) ) where:

    R = minimum radius curve

    v = vehicle design speed (MPH)

    e = rate of super-elevation (decimal of a foot rise per foot roadway)

    f = side friction factor

    Vehicle Design Speed (v) 30 40 50
    Side Friction Factor (f) 0.16 0.15 0.14

     

    c.

    Super-elevation when widening existing streets. Widening section along existing streets shall be designed reflecting existing curvature and super elevation, if any, unless the existing street has been included in a specific design by the city or GDOT which calls for different standards, in which case the project will be coordinated with the overall design.

    d.

    Super elevation runoff. Roadway edge curves shall be provided for tangent run out (bringing edge from a normal crown to centerline elevation) and super elevation runoff (from the end of tangent run out to the point of design super elevation) in accordance with design standards of GDOT or other professional engineering standards.

    e.

    Tangents and compound curves. Between reverse horizontal curves there shall be not less than the minimum centerline tangents shown in Table 3-15 unless otherwise specified by GDOT. Compound radii curves are prohibited. At least the "desirable" length shall be provided unless hardship conditions of topography or property configuration will not allow lengths greater than those shown as "minimum." For compound circular curves that cannot be avoided, the ratio of the flatter radius to the sharper radius shall not exceed 1.5 to 1.

    Table 3-13. Tangents

    STREET
    CLASSIFICATION
    MINIMUM
    TANGENT
    LENGTH (FT)
    Collector 100
    Nonresidential Local 75
    Local 50

     

    4.

    Horizontal and vertical clearances.

    a.

    Horizontal clearances.

    i.

    Shoulder width. A shoulder of no less than 11 feet from the back of curb or edge of pavement, appropriately graded and having gentle slopes of not more than 0.5 inch per foot and rounded cross-sectional design shall be maintained along all streets. Beyond the shoulder but within the right-of-way, slopes shall not exceed one foot of rise for each two feet of horizontal distance on a cut slope, and one foot of fall for each three feet of horizontal distance on a fill slope.

    ii.

    Clear zone. Experience has shown that motorists occasionally run off the roadway and providing a traversable recovery area can lessen serious injury. AASHTO publishes a Roadside Design Guide that should be used as a reference when designing driveways.

    iii.

    The following table provides the clear zone distances as contained in the Roadside Design Guide. Driveways must be designed so that all areas within the roadway right-of-way have clear zones as defined in the following table.

    Table 3-14. Clear Zone Distances (Refer to AASHTO Roadside Design Guide, latest edition)

    DESIGN
    SPEED
    DESIGN
    ADT
    FILL SLOPES CUT SLOPES
    6:1 or Flatter 5:1 to 4:1 3:1 3:1 5:1 to 4:1 6:1 or Flatter
    40 or Less Under 750 7—10 7—10 ** 7—10 7—10 7—10
    750—1500 10—12 12—14 ** 10—12 10—12 10—12
    1500—6000 12—14 14—16 ** 12—14 12—14 12—14
    Over 6000 14—16 16—18 ** 14—16 14—16 14—16
    45—50 Under 750 10—12 12—14 ** 8—10 8—10 10—12
    750—1500 12—14 16—20 ** 10—12 12—14 14—16
    1500—6000 16—18 20—26 ** 12—14 14—16 16—18
    Over 6000 18—20 24—28 ** 14—16 18—20 20—22
    55 Under 750 12—14 14—18 ** 8—10 10—12 10—12
    750—1500 16—18 20—24 ** 10—12 14—16 16—18
    1500—6000 20—22 24—30 ** 14—16 16—18 20—22
    Over 6000 22—24 26—32* ** 16—18 20—22 22—24

     

    Notes:

    * Clear zones may be limited to 30 feet.

    ** Fixed objects should not be present in the vicinity of the toe of these slopes. The width of the recovery zones should consider a number of factors including right-of-way availability, economic factors, safety needs, and accident history.

    All areas located within the clear zones should remain clear of obstructions such as bridge abutments, poles, trees, etc. If obstructions are unavoidable, the design should include appropriate protection such as break-away design, guardrail installation, safety end treatments on culverts, etc. The Roadway Design Guide includes a table for horizontal curve adjustments, where the clear zone correction factor is applied to the outside of curves only. Curves flatter than a 2,860-foot radius do not require an adjusted clear zone.

    iv.

    Increased clear zone in certain locations. At selected locations, such as the outside of a sharp curve, a wider clear zone with greater horizontal clearances to any roadside obstruction may be required.

    v.

    Removal of obstructions. The community development director, in accordance with Georgia Law 32-6-51 and this development ordinance, is authorized to remove or direct the removal of any sign, signal, device, or other structure erected, placed, or maintained on the right-of-way of a public road which because of its nature, construction, or operation, constitutes a danger to, or interferes with the vision of, drivers of motor vehicles.

    b.

    Vertical clearances. Vertical clearance for all overhead obstructions shall be at least 16 feet over the entire roadway width.

    Additional clearance may be required for obstructions over railroads, state or federal roadways or other transportation routes.

    F.

    Street intersections.

    1.

    Angle of intersection. The angle of roadway intersections shall be consistent with the requirements for driveways as set forth in this section.

    2.

    Intersection approaches: horizontal alignment.

    a.

    New local streets which approach an intersection with a street in a category higher than itself on a horizontal curve having a centerline radius less than 240 feet shall provide a tangent section of roadway at least 30 feet long. Collectors approaching an intersection with a major thoroughfare on a horizontal curve having a centerline radius of less than 550 feet shall also provide the 30 ft. tangent section. The tangent length shall be measured along the centerline of the street, from the right-of-way line of the intersecting street, extended, to the point of tangency with the centerline of the curve section.

    b.

    New major thoroughfares shall provide tangent sections at intersections with streets in equal or higher categories as needed to provide adequate stopping distances at their design speeds.

    3.

    Intersection approaches: vertical alignment.

    a.

    Approach landings internal to residential subdivisions. For approaches to intersections internal to a residential subdivision, a leveling of the street at a grade not exceeding five percent shall be provided for a distance of not less than 25 feet as measured from the back of curb of the intersecting.

    b.

    Approach landings at local streets. For new street intersections with local streets, a leveling of the street at a grade not exceeding three percent shall be provided for a distance of not less than 50 feet as measured from the back of curb of the intersecting street.

    c.

    Approach landings at collectors or arterials. As a street approaches an intersection with a collector or arterial, there shall be a suitable leveling of the street at a grade not exceeding two percent and for a distance not less than the following minimums:

    Table 3-15. Approach Distances at Major Intersections

    APPROACHING STREET CLASSIFICATION MINIMUM APPROACH TANGENT (1)
    Principal or Minor Arterial 100 feet
    Collector 75 feet
    Local (residential and nonresidential) 50 feet

     

    Notes:

    (1) Distance of the approach is measured from edge of pavement of the intersecting street to the point of curvature in the approaching street.

    4.

    Intersection radii.

    a.

    Intersection radii for roadways as measured at back of curb and for the right-of-way lines shall be as follows. The minimum roadway radii for the intersection of local and nonresidential local streets is 25 feet. For all other roadway classifications, the minimum roadway radius is 40 feet. When a local or residential collector intersects a higher classification of roadway, the radii shall be a minimum of 40 feet. Larger radii may be required for streets intersecting at an angle of less than 90 degrees; or when vehicle and operating circumstances dictate. As approved by the Director, the radii can be reduced a maximum of five feet for the following reasons:

    i.

    Separation from street, or

    ii.

    Removal of obstruction.

    b.

    Intersecting right-of-way lines may be joined by an arc having the minimum radius shown, or by a miter which cuts across the right-of-way lines connecting the points where the required radius would have otherwise been tangent.).

    5.

    Islands.

    a.

    Islands in street intersections shall conform to the design requirements of the standard drawings. In no case shall anything in an island extend more than three feet above the street grade within the right-of-way, except traffic regulatory devices and other infrastructure erected or approved by the city. No island shall be approved which contains less than 100 square feet for median islands or 50 square feet for corner islands.

    b.

    Islands with the right-of-way or access easements shall be constructed with mountable curb sections per GDOT specifications, unless otherwise approved by the Director.

    c.

    Islands are an important form of intersection channelization that is often needed to prohibit undesirable movements, define the paths of allowed movements, and provide a refuge area for pedestrians. Any location where two outbound lanes are proposed for a driveway at an un-signalized location, the right line must be for right-out only movement, and separated from the other lane by a raised island.

    d.

    Painted lines are an effective means to direct the paths of vehicular movement. However, raised islands are more effective during times when visibility is reduced. When islands are to serve as pedestrian refuge areas, they should be constructed as raised islands. All sign posts to be placed within concrete area must have hole through pavement structure. The hole may be either formed, drilled or sawed.

    e.

    When multiple crosswalks are required to pass through islands, the required size may exceed the 100 square feet mentioned above. The additional area may be required to install wheelchair ramps. As an alternate to ramps, the pedestrian travel way can be "slotted" through the island, remaining on the grade of the roadway.

    f.

    Raised islands should be offset from the edge of the adjacent travel lane on all sides. The amount of offset shall be a minimum of 18 inches as measured from the edge of the travel lane to the face of the curb. When raised islands are adjacent to roadways with posted speed limits of 50 MPH or greater, the island shall be offset from the edge of the roadway by a minimum distance of ten feet.

    6.

    Intersection corner sight distance.

    a.

    Intersections shall be designed with adequate corner sight distance. Where necessary, back slopes shall be flattened and horizontal or vertical curves lengthened to provide the minimum required sight distance. Using traffic control measures to meet intersection sight distance requirements shall not be allowed, with the exception of roundabouts or signals with the Director's approval.

    b.

    The minimum corner sight distance requirement may be calculated using AASHTO "Policy on Geometric Design of Highways and Streets," Chapter 9 (Intersections), latest edition. Intersection sight distance is determined with an assumed height of driver's eye of 3.5 feet and an assumed height of object of 3.5 feet when measuring in the vertical plane. When measuring in the horizontal plane, the intersection sight distance is determined with an assumed driver's eye location from a point four feet offset from the centerline and 15 feet from the edge of closest travel lane to a point along the centerline of the closest oncoming travel lane:

    fIG3-16.png

    Table 3-16. Minimum Corner Sight Distance

    DESIGN SPEED (MPH) SIGHT DISTANCE (FT) (1)
    2 LANES 3 AND 4 LANES 5 AND 6 LANES
    SDL=SDR SDL SDR SDL SDR
    25 280 n/a n/a n/a n/a
    30 335 350 375 400 420
    35 390 410 440 465 490
    40 445 470 500 530 560
    45 500 530 560 595 630
    50 555 590 625 660 700
    55 610 650 685 730 770

     

    Notes:

    (1) SDL refers to "Sight Distance to the Left" and SDR refers to "Sight Distance to the Right."

    (2) Minimum corner sight distance for stopped passenger vehicles turning onto a roadway with no median and grades of three-percent or less. Distances shall be adjusted for entering roadways with different design characteristics.

    7.

    Obstructing visibility at intersections. On any corner lot, within an area formed by the lot lines on the street sides of such lot and a line (miter) joining points on such lot lines located at a distance of 20 feet from the point of their intersection, the following shall apply:

    a.

    There shall be no fence or wall or hedge higher than three feet.

    b.

    There shall be no obstruction to vision, other than a post or column or tree (except standards erected by city) exceeding one foot in greatest cross-sectional dimension, between a height of three feet and a height of 15 feet above the established grade of either of the intersecting streets.

    c.

    The Director may require additional restrictions based on the horizontal or vertical curvature of the roadway or any unique design features of the intersection.

    8.

    Turning lanes at intersections. Left turning lanes shall be provided on all new internal project streets, classified as a collector or higher, intersecting a major thoroughfare, and may be required in other locations to meet traffic demand and safe operations. Right turning lanes may be required to meet traffic demands or safety concerns. When provided, turning lanes shall meet the criteria for turn lanes in this section.