Division Nine: Standards for Traffic Engineering

Chapter I. Introduction

Sec. 901-1 Purpose and Scope

This division establishes the minimum acceptable standards for the application of traffic engineering and traffic planning principals in the design of the transportation system to promote the safe, efficient and orderly movement of goods and people.

Chapter II. Traffic Studies

Sec. 902-1 Responsibility for Traffic Studies

Traffic studies may be required by the County in order to adequately assess the impacts of a development proposal on the existing and/or planned major street system.  These impacts would typically be addressed in the "Traffic Circulation" section of an Environmental Impact Report (EIR). If a full EIR is not required, a Negative Declaration, or an expanded initial study addressing traffic impacts, may be required.  The primary responsibility for assessing the traffic impacts associated with a proposed development shall be the developer's, with the County serving in a review capacity.

The following development proposals will require regional traffic studies prepared, in a format acceptable to the Kern County Public Works Department, unless the study is waived.

902-1.01 Any Project proposed within the Kern County General Plan, where a Transportation Impact Fee Program has not been implemented and the increase in project trip generation during any peak hour is expected to exceed 50 vehicles.

902-1.02 Any Project proposed within the Rosamond-Willow Springs Specific Plan where the increase in project trip generation during any peak hour is expected to exceed 50 vehicles.

902-1.03 Any General/Specific Plan Amendment application, which is expected to intensify land use over that previously allowed in the General/Specific Plan whereby the increase in trip generation during any peak hour is expected to exceed 50 vehicles.

Where proposed projects, as noted above, are not expected to result in an increase in trip generation, it is exempt from a regional traffic impact study.  To be eligible, a traffic analysis shall be submitted and approved which computes trip generation with proposed land uses. Said analysis shall show that increase in peak hour trip generation does not exceed 50 trips.

902-1.04 Special traffic studies may be required where special circumstances dictate the need for a traffic study (such as issues of safe access concerns, significant public opposition, request for deviation from standards, large commercial/ industrial centers, etc.).

902-1.05 Where access points are not defined at the time the traffic study is prepared, additional traffic work may be required when the access points are determined.

902-1.06 Transportation consultants are required to discuss projects with the Development Review Division prior to starting the study.

902-1.07 The traffic study shall be prepared, stamped and signed by a licensed Traffic Engineer or Civil Engineer experienced in preparing traffic studies.

Sec. 902-2 Traffic Study Format

In order to provide consistency and to facilitate staff review of traffic studies, the Caltrans “Guide for The Preparation of Traffic Impact Studies” shall be followed in the preparation of traffic studies.

DOT Transportation Planning

Facilities to be studied shall be any City, State or County facility (mainline, interchange, structure, intersection or any project on the Transportation Impact Fee (TIF) list) when the peak hour trip generation onto said facility exceeds 50 trips.  For those facilities currently experiencing level-of-service (LOS) "C" or less, the following "sliding scale" of "added peak project trips" shall be applied as the procedure to determine whether the facility should be included:

902-2.01 Project Trip Generation and Design Hour Volumes must be calculated using the data contained within the Institute of Transportation Engineer's (ITE) Trip Generation Manual, latest edition, or more appropriate local data as approved by the Traffic Engineer.  (Formula Averaging is NOT acceptable for the calculation of Peak Hour trip generation rates as published in the ITE Trip Generation Manual, latest edition.)

902-2.02 Capacity Analysis must be determined by the methods contained within the Highway Capacity Manual (HCM), latest edition.

902-2.03 Traffic Signal requirements will be determined by the warrants contained in the California Manual on Uniform Traffic Control Devices (California MUTCD), latest edition.

902-2.04 Proportionate Shares along State highways and County Roads shall be calculated using the Caltrans formula.

Chapter III. Tentative Subdivision Review

Sec. 903-1 Introduction

This chapter is intended as a standard for design and review of the traffic aspects of tentative subdivision maps.

Sec. 903-2 Street Name Signs

Street name signs shall be paid for and installed by the developer and placed in accordance with the requirements of County Standards Plate Nos. T-1 and T-2. These shall also be placed at the corner of knuckled streets.

Sec. 903-3 Regulatory/Warning Signs

Developer will be required to pay for and install regulatory and warning signs in accordance with these standards.  Traffic signs shall be installed in conformance with the standards in the latest California MUTCD.  In the event of a conflict between these standards and the California MUTCD, the California MUTCD shall take precedence.

Chapter IV. Traffic Signal Improvements

Sec. 904-1 Introduction

This chapter is intended as a standard for design and installation of traffic signal improvements.

Sec. 904-2 Traffic Signal & Lighting System Design

Traffic signals and lighting systems shall be designed to meet all County and State standards.  These standards are defined in detail by the Kern County Public Works Department, Traffic Engineering Division.

Chapter V. Line of Sight Review

Sec. 905-1 Introduction

This chapter is intended as a standard for the construction and restriction of improvements in the line of sight for vehicles entering and exiting county roads as required.

Sec. 905-2 Uncontrolled Intersections

At all corners located on uncontrolled intersections no obstruction to the driver's view in excess of three (3) feet above the adjacent gutter flowline shall be placed in a triangular area formed by the intersecting street curblines and a line connecting them at points 60 feet from the intersection point per Plate No. T-7.

Sec. 905-3 Alleys and Minor Driveways

No obstruction to sight view will be allowed within a triangular area formed by the alley or driveway edge and the interior sidewalk edge (the street right-of-way line if no sidewalk exists) and a line connecting them at points 10 feet from the intersection point.

Sec. 905-4 Controlled Intersections

905-4.01 Sight distance at controlled intersections shall be based upon a sight distance equal to design speed (S) in miles per hour multiplied by a factor of 10 (See Plate No. T-7). Design speeds for various street classifications are as follows:

905-4.02 Corner sight distance is measured from a point on the minor road fifteen feet from the curb line of the major road, and three feet right of the left edge of the viewing lane under consideration.  Said point is viewed from a height of three and one-half (3.5) feet on the minor road to an oncoming vehicle height of four and one-quarter (4.25) feet on the major road.

905-4.03 When viewing left, the location of the oncoming vehicle is considered to be twelve feet from the nearest curb line of the major street (six (6) feet with parking prohibited). Parking is assumed to be prohibited on arterial and collector streets.

905-4.04 When viewing right, the location of the oncoming vehicle is considered to be three (3) feet right of the left edge of the left most lane for the oncoming vehicle on the major street.

Sec. 905-5 T-Intersections

At uncontrolled T-intersections, the requirements of both Sections 905-2 and 905-4 shall be met.

Sec. 905-6 Landscaping

905-6.01 Landscaping over thirty (30) inches in height above top of curb shall not be placed within the lines of sight defined in the preceding sections.  All landscaping must be maintained at a height of thirty (30) inches or less with the exception of trees as provided for in Section 905-6.02 (See Plate No. T-8)

905-6.02 Trees are permitted in the line of sight for controlled intersections provided that the skirt height (bottom of foliage) is maintained seven (7) feet above the adjacent top of curb height.  In the event more than one (1) tree is placed in the sight line area they must be placed on a radial from the viewpoint. (See Plate No. T-8)

Chapter VI. Signing, Striping & Marking

Sec. 906-1 Introduction

The County shall provide all new and revised signing, striping, marking and other channelization necessary except as noted in Chapter III of this Division. However, design of all new and revised signing, striping, marking and other channelization shall be provided by the project’s Engineer and comply with the standards established in the State of California and detailed in the California MUTCD.

These requirements are intended to supplement and clarify the requirements contained in the California MUTCD and the CalTrans Standard Plans and Specifications, latest edition.

The associated details, special provisions and these requirements are to be used as a general standard for developing signing & striping plans. Specific situations may require special consideration.

Sec. 906-2 Design Requirements

906-2.01 Signing & striping plans shall show the proposed signing, striping and markings within the limits of the project. It shall also show existing signing and striping in and beyond the project limits as needed to determine proper transition.

909-2.02 Depending upon the location involved, various methods for dividing traffic may be available or appropriate. These include: a yellow skip stripe, double yellow stripe, double-double yellow stripe (painted median), two-way turn lane stripe and where there is a minimum specified ADT, reflective raised pavement markers will be required. The Traffic Engineer shall have final determination as to which method is used.

909-2.03 Paint shall conform to Section 84 of the Caltrans Standard Specifications, unless another treatment is allowed.

906-2.04 Existing stripes shall be removed, where necessary. Removal shall be in accordance to Section 15 of the Caltrans Standard Specifications.

906-2.05 Provisions shall be included to have the Inspector review the "Rabbit Tracked" layout in the field prior to final striping. Field adjustments may be needed.

906-2.06 It is the responsibility of the project's Engineer to review the road work to be done with relationship to maintaining existing traffic. If the project's Engineer determines a detour is needed, then a detour plan shall also be included. If no detour plan is provided but the Inspector finds that one is necessary during construction, then the project's Engineer shall provide such a plan at that time and no work shall progress until such plan is approved.

906-2.07 Plate Nos. T-12 and T-13 detail typical striping plans, which cover most of the common striping situations encountered. Striping plans shall be designed to provide the total number of lanes for ultimate full width improvements whenever possible. Specific projects may require special treatment to match existing conditions. (e.g. - dropping a lane or forcing the outside lane to turn at an intersection, providing only 2-lanes each way on a 6-lane arterial, moving lanes over due to 1/2 width improvements, etc.).

Chapter VII. Street Sign Specifications

907-1 Design

Street signs shall consist of two (2) double faced signs, mounted at right angles. (or 45 degree if angle of intersection warrants)

907-2 Bracket Assembly

Post cap shall fit a two (2) inch I.D. Round Pipe or two (2) inch Square Tubing, complete with minimum of three (3) Allenhead setscrews to secure to pipe. Crosspiece shall secure the name plates at 90-degree (or 45-degree) with a minimum of two (2) five-sixteenths (5/16) inch Allen head setscrews in each plate (setscrews shall be electro-plated zinc-coated.0003-.0005”). Casting shall be die-cast aluminum. Standard weight.

907-3 Plate Size

Length shall be either 30” or 36”. Width shall be nine (9) inches. Radius of corners shall be one-half (½) inch. Plates shall be 0.125” ga. aluminum, 6061T6 Alloy with Alodine 1200 surface treatment.

907-4 Finish

Signs shall be baked enamel finished in accordance with the current State of California Specifications of Interstate Green.

907-5 Lettering

The letters shall be the rounded type style conforming to the standard alphabet for highway signs designed by the “Standard Highway Signs and Markings” of the Federal Highways Administration (FHWA).  Street names shall be Series B, C, D, or E, six (6) inch high. Abbreviations (St., Dr., Ln., Ave., Ct., Way, etc.) shall be series C, two (2) inch high. Street names and abbreviations shall be White Reflective Sheeting Material, as manufactured by the 3M Company, or equal. Each name shall be individually laid out and spaced to fit either the 30” or 36” plates. Application of Reflective sheeting shall be applied in accordance with the manufacturer’s specifications.