Article II — ROADWAY DESIGN STANDARDS

(A) General requirements. (1) Scope. The design and construction of public and private roadways, alleys, driveways, bike paths and all associated appurtenances such as sidewalks, curbs, street lights, signs, barriers and the like in all unincorporated areas of the county, shall be in accordance with these minimum design standards, except as modified in any adopted specific plan. (2) Interpretation. The County Engineer shall be the final authority in any and all questions regarding the interpretation of these design standards, unless otherwise specified by adopted plan line. (3) Enforcement. Enforcement of these standards shall be by the County Engineer. (B) Definitions. Unless otherwise provided in this chapter, the following definitions shall be used in interpreting the provisions of this chapter.

ACCESS. The right of an owner of land to go and return from his or her own land to a public road. ALLEY. A secondary means of access to property and is located at the rear or side of the property. BICYCLE WAY. An area either within or outside the right-of-way of a dedicated street where bicycle travel is the designated use. COUNTY MAINTAINED ROAD. A road for which the county has accepted rights-of-way and maintenance responsibilities. CUL-DE-SAC STREET. A road open to motor vehicle use at one end only, with special provisions for turning around, and the further extension of which is precluded by the land division design. EASEMENT. The right to use another’s property. EASEMENTS are usually over a defined area and for a specific use such as public utilities facilities, drainage, sewers or access. FRONTAGE ROAD or SERVICE ROAD. A road immediately adjacent to freeways, expressways or arterials. These roads provides access to local properties that would otherwise front on the freeways, expressways or arterials. MEDIAN. That portion of a divided highway separating the traveled way for traffic in opposite directions. A MEDIAN may be raised, landscaped or painted. PARKWAY. The area adjoining the outer edge of the roadbed, extending to the right-of-way line in which sidewalks, plantings, utilities, bank slopes and related facilities may be located. PART-WIDTH ROAD. Any street in which the improved width is less than the width necessary for a normal full-width street. PEDESTRIAN WAY. A right-of-way designed for use by pedestrians and not intended for use by motor vehicles of any kind. A PEDESTRIAN WAY may be located within or outside of street right-of-way, at grade or grade separated from vehicular traffic. PRIVATE RIGHTS-OF-WAY. Any of the following: (a) Any right-of-way that has been offered for dedication, but has not been accepted by the county; (b) A legally established private easement for access; (c) A navigable waterway; (d) Roads shown on antiquated subdivision plats that are not county maintained roads; and (e) Public roads for which there is no legally established right-of-way or easement. PRIVATE STREET/ROAD. A roadway within a private development or a planned residential development whereby the street improvements remain in private ownership. PUBLIC ROAD. Any road which is open for unrestricted travel by the general public. A PUBLIC ROAD may or may not be dedicated to or maintained by the county. RESTRICTED ACCESS. The right of vehicular access has been dedicated to the county. A property owner no longer has a right to go to and from his or her property by vehicle over a right-of-way line which has restricted access. RIGHT-OF-WAY. An easement for the use of roads, water and waste water facilities, flood and drainage works, overhead and underground utilities or any related improvements. ROAD. Includes streets and highways, both public and private. The terms streets, road, roadways and highways are used interchangeably. ROAD includes the roadbed, all slopes, shoulders, side ditches, curb, gutters, sidewalks and all other related facilities with the right-of-way. ROAD SYSTEM. The classification of streets and highways by their diverse functions and design. The hierarchy of roads in the county and additional definitions of road classifications are shown in § 23.31.021. ROADBED. That portion of the road between curb-faces or between the outside line of improved shoulders. STUB STREET. A street open at one end only, without provisions for turning around. TRAVELED-WAY. That portion of the road for the movement of vehicles, exclusive of shoulders and auxiliary lanes. (C) Other standards. It is recognized that it is not humanly possible to set rigid design standards for every possible design situation that may be encountered. When the situations arise, design of roadway improvements shall adhere to sound engineering principals and good civil engineering practice. State of California Department of Transportation references titled Manual of Traffic and Highway Design Manual may be used for guidance. In all cases, final approval of any design is left to the discretion of the County Engineer. (D) Access required. All parcels in a development project shall have access to a county maintained road either directly or by private right-of-way or easement offered for dedication to the county. The use of private right-of-way or easement for access shall be approved by the Planning Commission or County Engineer.

(E) Improvement required. The developer shall improve all roads that are a part of the development project or are required to serve the development project in accordance with the requirements of this chapter. Roads must be dedicated to the county. For a building permit, all projects along existing roads shall construct road improvements on the project side of the roadway along the parcel frontage as required to meet county standard road sections. Private roads shall be developed to public road standards. (Ord. 860, § 4 (part), 2010)

(A) Common private driveway. (1) A secondary access street with improved 30 foot minimum right-of-way; (2) Private maintenance; (3) Common private driveways in commercial and industrial areas shall only be allowed with the specific approval of the Planning Commission and the County Engineer; and (4) Where new development adjoins an existing common private driveway, improvement to the driveway shall be required if not to county standards. (B) Bicycle way. (1) “Bicycle way” and “bike path” are used interchangeably. Typical width for a separated bike path is a eight-foot improved surface in a 20-foot dedicated easement, the remainder being landscaped according to a landscaping plan approved by the County Engineer. (2) Where road right-of-way widening is required in lieu of separated bike paths, an additional 12-foot dedicated width is required with two paved six-foot bike ways provided, one for each direction of travel. (3) On-street bike lanes shall be delineated with special marking, striping and signage as required by the County Engineer. (4) Off-street bike paths shall be delineated with special marking, striping and signage as required by the County Engineer. (C) Cul-de-sac. (1) Cul-de-sac roads shall be two-lane undivided roads with intersections at grade. (2) Driveway access to abutting properties is allowed. (D) Residential (through). (1) Through residential roads shall be two lane undivided roads with intersections at grade. (2) Driveway access to abutting residential lots is allowed. (E) Collector non-access. (1) Collector non-access shall be two-lane undivided roads with intersections at grade, designed to take a minimum interference of traffic from driveways. (2) Parking not allowed on street. Widening of the right-of-way for turn lanes at major intersections shall be provided. (F) Collector-access. (1) Collector-access shall be undivided four-lane roads with intersections at grade and partial control of access. (2) On street parking may be allowed in urban or suburban areas. Widening of the right-of-way for turn lanes at major intersections shall be provided. (3) Access from abutting single-family residential properties is prohibited. Access from commercial, industrial and multi- family properties may be allowed with approval of access design by the County Engineer. (G) Arterials. (1) Arterials shall be four- or six-lane divided roads with intersections at grade and partial control of access. (2) Major arterials require widening for turn lanes at major intersections. On-street parking is prohibited. (3) Access to abutting properties is prohibited except commercial or industrial zoned properties may be allowed access subject to design approval of the County Engineer. Direct access is prohibited from abutting residential zoned properties. (H) Expressways. (1) Expressways shall provide no direct access to abutting properties. Intersections are limited to freeways, major and minor arterials and rural collector roads only. Intersections closer than one- quarter mile prohibited.

(2) Expressways may be two-lane or multi-lane undivided highways in rural areas or multi-lane divided highways in urban areas at the discretion of the County Engineer. (3) A minimum standard right-of-way shall be required plus additional widening for turn lanes at intersections. On street parking is prohibited. (I) Freeways. (1) Freeways shall be multi-lane divided highways with no direct access to abutting properties and have grade separations at intersections. Intersections are only allowed with freeways, expressways, arterials or rural roads. (2) Specific design standards, right-of-way width requirements and required appurtenances shall be determined by the County Engineer on a case by case basis.

(A) Responsibility. (1) The county will prepare or contract for preparation of any traffic studies. When submitted by the applicant, the study shall be reviewed by an independent consultant hired by the county or the county itself, and paid by the applicant through the county. (2) The developer shall deposit with the county funds for all costs prior to county preparing any required traffic studies. (B) When required. (1) Unless waived by the County Engineer, the county shall prepare a written traffic study for a development project when traffic caused by the development project is expected to exceed 50 trip ends during any day. (2) (a) At the request of the County Engineer, the county shall prepare a written traffic study for a development project when traffic caused by the development project is expected to be less than 50 trip ends during any day. (b) If traffic is less than 50 trip ends during any day, a traffic study will not normally be prepared unless there are special extenuating circumstances, such as traffic safety concerns. (C) Supplemental study required. The county may prepare a supplemental traffic study if, after preparing an original traffic study for any development project, the property use is changed so that total trip generation is increased by more than 15%. (D) Content. To provide consistency and facilitate review, the following format shall be followed for organizing information gathered, traffic assumptions, analysis, findings and mitigation measures: (1) Introduction; (2) Existing circulation system; (3) Existing traffic conditions; (4) Trip generation; (5) Trip distribution and assignment; (6) Traffic impacts; (7) Cumulative traffic conditions; (8) Cumulative impacts; and (9) Mitigation measures.

(A) Soil report required. All public and private roadway designs shall be based on the results of a soil investigation performed by a registered geotechnical engineer or a registered civil engineer with expertise in soil investigation. The report will address roadbed foundation conditions, grading considerations, slope stability (for slopes in excess of 15%) and special conditions expected, such as highly organic or soft soil or shallow bedrock, which may affect design or construction. The report shall specifically determine the design resistance (“R”) value of native materials at the proposed subgrade elevation to allow proper design of the roadbed structural section. (B) Structural section. (1) Thickness. (a) All roadway designs shall be based on the recommendations of the required soil report. The thickness of the structural section elements shall be determined from the structural pavement design chart in the standard plans. (b) A minimum asphalt concrete (A.C.) thickness of two inches shall be used on all streets except collectors, arterials

and expressways where the minimum A.C. thickness shall be three inches. (2) Traffic indexes (T.I.). Traffic indexes shall be determined in the traffic report or as required by the County Engineer. The following minimum shall apply: T.I. T.I. Common private driveway

Per CALTRANS

(C) Design speed. (1) Design of all roads shall be consistent with the speeds expected and shall follow the recommendation of the traffic report. The following speeds shall be the minimum allowed for road design: Classification Minimum Design Speed Classification Minimum Design Speed Common-private drive 10 mph Cul-de-sac 20 mph Local/residential through street 30 mph Collector 40 mph Rural road 50 mph Arterial 60 mph Expressway 70 mph Freeway Per CALTRANS

(2) The County Engineer may require higher design speeds at locations where higher speeds may occur.

(D) Horizontal layout. (1) Intersection offsets. Streets located on opposite sides of an intersecting street shall have their centerlines directly opposite each other, otherwise the centerlines shall be separated by not less than 150 feet for local roads and 300 feet for collectors. Arterials and expressways shall be intersected only by collectors or higher classification roadways and only at intervals acceptable to the County Engineer. (2) Continuation of existing streets. New subdivision streets that are continuations of existing streets shall be aligned so that their centerlines coincide. In cases where straight continuations are not physically possible, centerlines shall be continued by curves. (3) Horizontal curves. (a) Minimum curve radii. The minimum centerline curve radii, except where physical conditions make compliance impractical, shall be as follows: Minimum Centerline Radius Minimum Centerline Radius Expressways 2,400 Arterials 1,800 Collectors-access 1,200 Collectors-non access 1,200 Local/residential-through street 300 Residential cul-de-sacs 100 Common private driveway 60

(b) Tangent length between curves. The minimum tangent length between reversing curves shall be 250 feet for expressways, 150 feet for arterials and collectors and 100 feet for all other classifications, except 50 feet for private drives or as approved by the County Engineer. Broken back curves are not allowed. (c) Compound curves. The use of compound curves should be avoided where possible. Where special topography or other conditions exist, the use shall be as approved by the County Engineer. (4) Corner radii. The corner property line, curb line and edge of pavement radii at street intersections shall be as follows:

Type of Intersection Required Radius Ft. Cul-de-sac and local 20 Collectors 25 Arterial or expressway 35 The highest classification of the intersecting roads shall govern.

(5) Intersection angle. Streets shall intersect at an angle as near to 90 degrees as practical and not less than 80 degrees. The central angle on the property line corner curve of adjacent corners shall be within ten degrees of each other. Intersections shall be designed on tangent sections at least 50 feet beyond the right-of-ways for the intersecting roads. (6) Cul-de-sac streets. Cul-de-sac streets may be allowed as follows: (a) Maximum length. Cul-de-sac streets shall not exceed the lengths specified herein. In no case shall more than 50 dwelling units be served by a cul-de-sac street. (b) Turnaround. Cul-de-sac streets shall be terminated by an improved turnaround having a minimum right-of-way radius of 50 feet. (c) Alternate turnaround. Hammerheads, loops, offset bulbs and other geometric designs may only be used under special circumstances and only with the approval of the County Engineer. (7) Sight distance at intersections. Streets shall not be designed with intersections on the inside of curves or at any location in general where sight distance will be inadequate for drivers to tell if they can safely enter the traffic flow or cross the street. The minimum distance from an intersection to a curve shall be determined according to the California Department of Transportation Highway Design Manual. Exceptions may be made by the County Engineer for especially difficult design circumstances only if visibility easements to provide adequate sight distances are established. In lieu of visibility easements, additional street right-of-way may be dedicated. (8) Horizontal sight distance. (a) Where objects that may obstruct a driver’s vision are adjacent to the roadway, the design of horizontal curves shall be such as to attain the required stopping site distance as set forth in the California Department of Transportation Highway Design Manual, latest edition. (b) Where a driveway or roadway intersects a roadway with a curved centerline, a limited use area, clear of obstructions, including parking, landscaping walls and structures, shall be maintained for sight distance. The areas shall be delineated on the improvements plans and restricted by map provisions or by deeds. (E) Profile standards. (1) Minimum grades. The minimum grade in all streets shall be 0.25 %. This minimum may be reduced to 0.20% around the outside of horizontal curves. Flowline grades in cul-de-sac shall be maintained at a minimum of 0.25%. These restrictions do not refer to centerline grades of vertical curves. Curb and gutter elevations on vertical curves shall be adjusted to meet a 0.25% minimum grade. Where matching existing conditions, minimum grade may be reduced only with the approval of the County Engineer. (2) Cross slopes. The standard cross slope shall be 2%. For street widening projects, the minimum cross slope shall be 1.5% and the maximum cross slope shall be 3%. Superelevated sections may deviate from this section. The cross slope of a street widening project shall match the cross slope of the existing pavement whenever possible. Road widening cross- slope must equal or exceed cross-slope of existing, or overlay to a constant cross-slope will be required. (3) Vertical curves. (a) Required. Vertical curves shall be required whenever the algebraic difference of grades is 1% or greater for local streets and 0.5% or greater for collectors, arterials, expressways and rural roads. (b) Minimum length. The minimum length of vertical curves shall be determined by consideration of passing and stopping distance requirements, headlight sight distance, drainage control and aesthetic appearance. Where other considerations do not govern the minimum length of the vertical curve for collectors, arterials and expressways, shall be L=AV2/46.5 at sags and L=AV2/150 at crests, where A is the algebraic difference in grades in percent divided by 100 and V

is the design speed in miles per hour. In no case shall less than 100 feet be used. (4) Stopping sight distance. The minimum stopping sight distance shall be measured from a point three and one-half feet above the pavement surface (assumed height of driver’s eyes) to a point one-half feet above the pavement (assumed object height). Minimum distances are as follows: Recommended Design Speed Minimum Stopping Sight Distance Recommended Design Speed Minimum Stopping Sight Distance 10 mph 50 feet 20 mph 125 feet 30 mph 200 feet 40 mph 300 feet 50 mph 430 feet 60 mph 580 feet 70 mph 750 feet

(5) Intersections. Profile of intersecting streets shall have a maximum slope of 3% within 50 feet of the curb line of the

intersection. Variations to this requirement may be approved by the County Engineer for unusually steep terrain or other extenuating circumstances. (F) Curb, gutter and sidewalk. (1) Curb, gutter and sidewalk is required in urban and suburban residential areas (minimum lot size less than five acres). (2) Curb, gutter and sidewalk in commercial or industrial areas shall conform to conditions of development approval. (3) Curb, gutter and sidewalk on arterials and expressways may be required in urban and suburban areas. (4) Cross gutters are not allowed on any road except local residential roads with the approval of the County Engineer. The developer shall submit evidence that the intersection cannot reasonable be drained to an underground system before cross gutter will be considered. (5) Median curbs may be constructed using modified type B curb. (6) Barrier curbs may be required by the County Engineer at such locations as deemed necessary to control drainage, delineate traveled ways, provide for safe pedestrian and vehicular passage and the like. Where required, barrier curbs shall conform to Type A1-6 of the California Department of Transportation Standard Plans. (7) Handicapped ramps shall be constructed at all curb returns in residential and commercial areas and at such other locations required by the County Engineer. Ramps shall conform to standard drawing. (8) Sidewalk widths shall be measured from face of curb to back of walk. Minimum widths shall be per applicable standard drawing. (9) Sidewalk widening may be required at the discretion of the County Engineer in areas such as school zones, local commercial areas, bus stops, rural postal drop boxes, near bicycle ways and trails or other areas deemed appropriate. Where sidewalk widening is required, the County Engineer shall give width, length and transition requirements. (10) In special situations with the approval of the County Engineer, sidewalks may be separated from the curb and gutter by a landscaping strip. The developer shall submit complete detail of proposed dimensions and landscaping. (G) Driveways. Driveway design shall conform to approved standard drawings. (H) Sound barrier design. (1) Location requirements. Sound barriers may be required along the rear and side property lines of residential developments adjacent to limited access roads and other ground level noise elements to achieve the noise control objectives of the county’s general plan noise element or conditions of development approval. (2) Sound study. When it appears to the County Engineer that a sound barrier may be necessary or when a sound barrier is a condition of development, a sound study prepared by an acoustical consultant shall be submitted to the Department of Public Works before the improvement plans will be approved by the County Engineer. The sound study shall include a recommended height and termination points for the sound barrier including all backup material leading to the recommendations. (3) Design. (a) The sound barrier shall be designed to conform to levels in the general plan at the affected building setback line or as required by the Department. (b) The County Engineer may approve new sound barriers upon request. The request shall include plan details and

calculations prepared and signed by an appropriate consulting engineer. (c) Sound barriers shall be designed for a minimum service life of 30 years. (d) Sound barriers normally will not be allowed within public rights-of-way. (4) Plan requirements. All construction details for sound barriers, including the locations and limits, shall be shown on the site improvement plans. (I) Survey monuments. (1) Required locations. The developer shall place permanent survey monuments at the locations shown on standard drawings. (2) Map Act compliance required. Qualifications of persons setting monuments, ties to nearby permanent objects and preparation of all required maps to be recorded shall rigidly adhere to the requirements of the State of California Subdivision Map Act, Land Surveyors Act and Professional Engineers Act. (3) Protection of existing monuments. All improvement plans shall contain a note stating that the contractor is responsible to preserve and protect all existing survey monuments or other survey markers. Any monuments, damaged, displaced, obliterated or lost shall be re-established or replaced by persons authorized to practice land surveying at the contractor’s sole expense. (J) Signage. (1) Barricades. Barricades shall be required at the end of the paved section (or traveled way for non-paved street) of all terminating streets. Barricades shall comply with standard drawing. (2) Street names. (a) All street names for new streets shall be named by the developer subject to the approval of the Communications Department. Duplicate names, near duplicate and phonetically similar names to street names already in use shall not be allowed. Names with more than 13 letters are not allowed. (b) To the extent possible, extensions of existing streets or streets that will in the future be part of a planned existing street extension, shall have the same name as the existing street. (c) Street names and street name sign locations shall appear on plans submitted for approval. Sign details shall be as shown on standard drawing. (3) Street sign locations. (a) Minor intersections. One street name sign installation [with two sign plates (four faces) on each post] is required at each intersection where each intersecting street has a right-of-way width of less than 84 feet. At a four-way intersection, the installation shall be located on one of the far right-hand corners of the intersection relative to the street having the greater right-of-way width or relative to the more important street if the right-of-way widths are equal. (b) Major intersections. Two street name sign installations [with four sign plates (four faces) on each post] are required at each intersection where one or both of the intersecting streets has a right-of-way width of 84 feet or greater. At a four-way intersection, the installation shall be located on both far right hand corners of the intersection relative to the street having the greater right-of-way width or relative to the more important street if right-of-way widths are equal. (c) Asymmetric intersections. For asymmetric intersections, or for expressways, arterials and freeways, street sign location shall be determined by the County Engineer. (4) Traffic signs. Traffic signs, including warning signs, information signs, speed limit signs and the like shall be installed for all streets as required by the County Engineer. Signage shall conform to the requirements of standard details. Where required signs are not detailed in the standard drawings, California Department of Transportation Traffic Manual, Highway Design Manual and Manual of Uniform Traffic Control Devices (MUTCD) shall be used for guidance on sign size, shape, lettering and location, subject to the approval of the County Engineer. (K) Striping and marking. Design of pavement striping and marker placement shall be in accordance with State of California Department of Transportation Traffic Manual and MUTCD subject to the approval of the County Engineer. (L) Bridges and overpasses. (1) Bridges and overpasses spanning 20 feet or more shall have their structural elements designed by an Engineer with appropriate registration who shall obtain the approval of the County Engineer for all design assumptions. (2) The design width of overpasses and bridges shall be the full width of the right-of-way unless narrower widths are approved by the County Engineer. (3) Bridges over water courses shall be designed such that a three-foot freeboard is provided between the 100-year design flow water surface elevation and the lowest portion of the bridge span. Detailed hydrologic and hydraulic calculations shall be submitted by a Registered Civil Engineer to document the 100-year water surface elevation. (4) The geometric design on bridges and the approaches on either side shall consider the potential for bridge icing

during extreme weather conditions, particularly in higher elevation areas of the county. Curved alignments should be avoided. (M) Street lights. (1) When required. (a) Street lights shall be required whenever the County Engineer deems them necessary to provide vehicular safety during hours of darkness. In general, street lights are required in urban and suburban areas, at local street intersections, along collectors, local commercial and industrial roads and minor arterials. Expressways, major arterials and freeways shall have special lighting considerations at turning pockets, intersections and interchanges. (b) Street lights are generally not required in rural areas along rural roads except at intersections or at the direction of the County Engineer. (2) Relocation. Existing street lights that must be relocated, repositioned or reconfigured as a result of construction of new streets, widening of existing streets or construction of driveways into a development shall be the responsibility of the developer. (3) Utility company authorization. A written notice from the serving utility company stating that line clearances and service requirements have been checked and are adequate shall be submitted to the County Engineer for all developments. (4) Luminaries. The type of street light and the appropriate wattage shall be specified on the plans. Luminaries shall be high pressure sodium type with internal ballast unless otherwise specified by the County Engineer. (5) Existing utility-owned poles. (a) Where there are existing or planned utility owned poles adjacent to the roadway, street light installation must be coordinated with the utility company. Whenever possible street lights should be installed on existing utility poles, and planned street light locations may be adjusted up to 25 feet to use an existing utility pole. (b) In the Pacific Gas and Electric Company (PG&E) service area, the developer shall arrange with PG&E to install PG&E owned and maintained street lights on PG&E poles in accordance with current utility rate schedules. (6) Design standards. Street lighting shall be designed in accordance with these standards, the construction specifications and the American National Standards Institute, “American National Standard Practice for Roadway Lighting”. (7) Calculations required. All data and calculations supporting the street light design and location shall be submitted to the County Engineer for review with the improvement plans.