Difference between revisions of "Streetlight Design Manual"
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==== Residential Streets: ====
==== Residential Streets: ====
Poles for residential streets shall be round, tapered aluminum poles for 15-foot mounting heights.
Poles for residential streets shall be round, tapered aluminum poles for 15-foot mounting heights.
==== Collector Streets: ====
==== Collector Streets: ====
Poles for collector streets shall be round, tapered aluminum poles for 30-foot mounting heights.
Poles for collector streets shall be round, tapered aluminum poles for 30-foot mounting heights.
==== Thoroughfare Streets: ====
==== Thoroughfare Streets: ====
Poles for thoroughfare streets shall be round, tapered aluminum poles for 40-foot mounting heights.
Poles for thoroughfare streets shall be round, tapered aluminum poles for 40-foot mounting heights.
=== Luminaire Bracket Arms: ===
=== Luminaire Bracket Arms: ===
Revision as of 15:54, 29 June 2015
General Purpose of the Design Manual:
This Streetlight Design Manual has been written to serve as a general guideline when designing a streetlighting system for the City of Overland Park, Kansas. Although there are specific design requirements, the guidelines contained herein should not be a substitute for proper engineering design and judgment based on specific project situations. The purpose of this Streetlight Design Manual is to aid consultants as well as City of Overland Park staff to be consistent in the practice of designing streetlighting plans. It provides an overview of what tasks are expected to be included in the scope of the design; what information should be included on the plan sheets; what kind of backup design information is required for proper analysis; and what is expected for the final deliverable product. Any questions regarding this manual may be directed to Bruce Wacker, P.E., Assistant City Traffic Engineer at the City of Overland Park, Kansas at (913) 895-6027 or by email at email@example.com.
Purpose of Streetlighting:
The principal purpose of lighting is to provide improved visibility for the street users so they can make quick, accurate and safe decisions. Street users include vehicle operators, bicycle and motorcycle operators and pedestrians. Light that falls on pedestrian walkways enhances pedestrian traffic, but the streetlighting criterion does not mandate specific lighting levels on sidewalks, bike paths or other pedestrian paths. The Planning and Development Services Department has separate criteria for the lighting of pedestrian facilities and should be consulted. This document does however, mandate specific lighting levels at the conflict points of pedestrians and vehicles, such as at intersection crossing points.
Reference to Other Documents:
Wherever applicable, this design manual should be used in conjunction with the American National Standard Practice for Roadway Lighting Illuminating Engineering Society of North America, RP-8-14, as herein modified and the National Electric Code by the National Fire Protection Association. The current editions of the City of Overland Park Streetlighting Resolution, Design and Construction Standards, Volume 1 Design Criteria (latest edition), Technical Streetlighting Construction Specifications, Standard Details and the Approved Materials List, hereafter referred to as “City Standards” should be followed during the design of any streetlighting project.
Public or Private Ownership, Operation and Maintenance:
Different policies apply to streetlighting systems based on the final ownership, operation and maintenance of the system. The two types of systems are 1) those that are installed in the public right-of-way that will be owned, operated and maintained by the City of Overland Park and 2) privately owned streetlighting systems that are installed in the public right-of-way that will not be owned, operated and maintained by the City of Overland Park. Although each of the systems will be discussed, the design guidelines contained herein only apply to systems that are within the public right-of-way that are owned, operated and maintained by the City of Overland Park.
City-Owned, Operated and Maintained Lighting Systems:
- All City-owned, operated and maintained lighting systems shall be designed in accordance with the design criteria listed herein and use all pre-approved materials from the City’s Approved Materials List, which is available at City Hall or from the City’s web page http://www.opkansas.org/doing-business/civil-engineering/approved-materials-list/. All lighting systems that are being designed in conjunction with the development of any public street or any developments that require modification of any streetlighting system within the public right-of-way by private consultants working for a developer are required to meet City Standards if the City will assume all ownership, operation and maintenance responsibilities after final acceptance of the project.
Privately Owned, Operated and Maintained Lighting Systems:
- All lighting systems within the public right-of-way that have been designated “privately owned” are not required to be constructed using City approved materials. However, the lighting system shall still be designed in accordance with the design criteria listed herein for average maintained light levels and uniformity ratios for the specific functional roadway classification and pedestrian conflict area classification and be constructed in accordance with the National Electric Code, current edition to ensure safe operation.
- All proposals for privately owned, operated and maintained lighting systems shall be pre-approved by the Overland Park City Council prior to final plan approval and execution and recording of the City standard maintenance agreement with the Johnson County Records and Tax Administration. If at any time, the homes association or other political subdivision requests the City to assume ownership of the lighting system, the streetlighting maintenance agreement establishes specific items that would need to be addressed before the request would be considered. One requirement is that the current streetlighting system would be have to be replaced with equipment meeting the current City Standards at the sole cost of the current owner.
- Privately owned streetlighting systems shall not be permitted to connect to any City-owned streetlighting system, whether it is poles, control centers, cable, junction boxes, etc. unless otherwise stipulated in the maintenance agreement.
The following section addresses the design criteria used for streetlighting in the City of Overland Park depending on the various types of lighting being considered. There are two types of streetlighting design used within the City of Overland Park: 1) Continuous lighting and 2) Safety lighting. Continuous streetlighting is required for all collector and thoroughfare designated streets. Safety lighting should be used for residential designated streets. There are specific lighting criteria for each of the two types that will be discussed.
Continuous lighting is defined as streetlighting that is designed to provide specific average maintained light levels and uniformity ratios between adjacent poles in accordance with the functional classification of the street and the corresponding pedestrian conflict area classification. Continuous lighting design shall be required for all collector and thoroughfare street classifications.
The following streetlighting design criteria will be used for all thoroughfare streets and collector streets, whether improved or unimproved, regardless of the number of through travel lanes and auxiliary lanes, as identified on the latest edition of the City of Overland Park “Official Street Map”, and the “Future Development Master Plan” available from the Planning and Development Services Department.
Functional Street Classifications:
- The “major” street classification includes all thoroughfare streets whether divided or undivided; whether improved or unimproved; and whether two-lane, four-lane or six-lane excluding auxiliary left and right turn lanes.
- The “collector” street classification includes all super-collector, residential collector streets, apartment streets, commercial streets and industrial streets regardless of the number of lanes; whether improved or unimproved.
Pedestrian Conflict Area:
- The “high” pedestrian conflict area includes areas where significant numbers of pedestrians are expected to be on the sidewalks or crossing the streets during darkness. These are typically areas that are in the “Nonresidential Category” zoned for “commercial” or “mixed-use” such as retail areas, near theaters, or major pedestrian generators.
- The “medium” pedestrian conflict area includes areas such as libraries, apartments, neighborhood shopping and schools which would be considered in the “Nonresidential Category” and zoned as either “public and semipublic” or in the “Residential Category” that would be zoned as either “high-density” or “medium-high density”.
- The “low” pedestrian conflict area includes areas in the “Residential Category” zoned as “medium-density” or “low-density” such as single family residential housing or duplexes.
- The maintained averages for luminance, as listed in Table 1, shall be met or exceeded for all continuous lighting designs. The corresponding uniformity ratios and/or veiling luminance ratios shall be equal to or better than those listed in the following table for luminance.
Table 1: Luminance Criteria Street and Pedestrian Conflict Area Luminance Criteria Functional Street Classification Pedestrian Conflict Area Maintained Average (Lavg)
Uniformity Ratio (Lavg:Lmin)
Uniformity Ratio (Lmax:Lmin)
Veiling Luminance Ratio (LVmax:Lavg)
Thoroughfare High 1.2 3.0:1 5.0:1 0.3:1 Medium 0.9 3.0:1 5.0:1 0.3:1 Low 0.6 3.5:1 6.0:1 0.3:1 Collector High 0.8 3.0:1 5.0:1 0.4:1 Medium 0.6 3.5:1 6.0:1 0.4:1 Low 0.4 4.0:1 8.0:1 0.4:1
Safety lighting is defined as lighting that does not provide specific maintained light averages and uniformity ratios between adjacent poles in accordance with the functional classification of the street and corresponding pedestrian conflict area classification. The purpose of this type of lighting design is to provide enough light on the street to enhance the safety of the street users but to avoid over lighting the area. All residential streets shall be designed based on the safety lighting design parameters.
Since June 11, 1979, the City policy has been not to continuously light residential streets. Only" partial" or "safety" lighting is provided. All street lights on residential streets will be installed in conformance with the following basic guidelines.
At Intersections with Other Residential Streets:
- In order to provide lighting within the conflict area of two residential streets, a light pole will be installed on one corner of an intersection or opposite the intersection in the case of a T-intersection. (See Figure 1)
On the Same Side as the Sidewalk:
- Streetlights should generally be installed on the same side of the street as the sidewalk unless there are significant utility or storm sewer conflicts. Any variance from this practice should be approved by the engineer or project manager.
Near Intersections with Another Pole Oriented in a Different Direction:
- Where an intersection has a light pole located at the corner but the luminaire is oriented toward the direction of the primary local street, a second light pole may be located on the secondary local street oriented in the direction of its centerline as long as the light pole is installed greater than 50’ from the back of curb line on the primary local street extended, and it is not on the same corner as the light oriented toward the primary street. (See Figure 1)
Within Cul-de-Sac Bulbs:
- A light pole will be installed within the cul de sac bulb when the cul-de-sac street is longer than 200 feet measured from the intersection of the intersecting streets to the center of the cul-de-sac bulb. (See Figure 2)
At Changes of Roadway Alignment:
- A light pole will be installed at changes of alignment of 60 or more which are 200 feet or more from an intersection, measured from the intersection of the local street centerlines, to the middle of the curve radius along the centerline of the local street, (See Figure 3)
Mid-block Street Lights:
- A minimum number of mid block street lights will be installed in order to achieve a desired pole spacing of approximately 250 feet. The maximum spacing between lights should not exceed 280 feet and the minimum spacing between lights should not be less than 225 feet unless otherwise approved by City staff. Lights should desirably be located on or near a property line and not in front of window lines if avoidable.
Intersections pose the highest conflict area for both vehicles and pedestrians. Therefore, the light levels should be higher for intersections than each individual street. The illuminance method, rather than the luminance method is the recommended design for intersection lighting. The following design criterion has been established for the illumination at street intersections.
|Functional Street Classification||Average Maintained Illumination
at Pavement by Pedestrian Area Classification, (Fc)
|Thoroughfare / Thoroughfare||34.0 / 3.4||26.0 / 2.6||18.0 / 1.8||3.0:1|
|Thoroughfare / Collector||29.0 / 2.9||22.0 / 2.2||15.0 / 1.5||3.0:1|
|Thoroughfare / Local||26.0 / 2.6||20.0 / 2.0||13.0 / 1.3||3.0:1|
|Collector / Collector||24.0 / 2.4||18.0 / 1.8||12.0 / 1.2||4.0:1|
|Collector / Local||21.0 / 2.1||16.0 / 1.6||10.0 / 1.0||4.0:1|
|*Local / Local||NA||NA||NA||NA|
*Intersection lighting analysis is not required for local / local street intersections. The criterion is satisfied if a light is placed at each intersection.
The intersection lighting grid is defined as the quadrilateral whose adjacent sides intersect at the midpoint of the curb radii at the back of curb (See Figure 4). The amount of light should be proportional to the classification of the intersecting streets and be equivalent to the sum of the values used for each separate street. If an intersecting street is illuminated above the recommended value, then the intersection illumination value should be increased proportionately. Intersections of collector and thoroughfare streets with local streets should be illuminated according to Table 2 above since criteria has not been established for continuously lighting local streets.
Streetlighting Installation Determination:
The following information has been established for all City-owned and maintained streetlighting systems installed in public right-of-way. The following explains when streetlighting will be installed. Additional information is contained in Resolution No. 4036, A Resolution Establishing Policy for City-Owned Streetlighting, and the Overland Park Municipal Code, Chapter 13.10.
Local Residential Streets:
There are four main distinct scenarios identified in which street lights will be considered for installation. They are 1) streets with existing City-owned street lights, 2) streets that do not have any streetlighting, 3) streets that have streetlighting that was purchased from Kansas City Power and Light (KCP&L), and 4) new streets that are being constructed either through the City’s Capital Improvement Plan (CIP) or by developers.
Residential Streets with Existing City-owned Streetlighting:
- Where street plans were approved prior to February 7, 2011, the City will replace or modify the existing streetlighting system with a new streetlighting system meeting the current streetlighting resolution as the street(s) are reconstructed as part of a major residential street reconstruction program. This does not include general pavement rehabilitation programs such as micro-surfacing, chip seal or residential street overlay programs. The City will not consider requests or petitions to upgrade the existing streetlighting system to the current standards unless all other lighting obligations within the City have been met, including replacement of Kansas City Power and Light Company street lights the City has purchased and streets that currently do not have any streetlighting.
Residential Streets with no Existing Streetlighting:
- Where City streets do not have any existing streetlighting, the City will consider streetlighting using City at Large funds if a petition from over fifty (50) percent of the residences along the street(s) to be lighted is received and verified. Only one signature is allowed per residence on the petition. The City is responsible for receiving and verifying petitions which can be obtained from the Public Works Department. Verified, valid petitions will be listed for Public Works Committee consideration. The Public Works Committee in turn will make recommendations to the City Council for construction of local residential streetlighting consistent with the amount of funds budgeted for that purpose. When requests exceed funding, priority will be given to those local residential streets with the most police reports of nighttime crime and nighttime traffic accidents.
Residential Streets with Existing KCP&L Streetlighting that was Purchased:
New Residential Streets
- Where street plans were approved on or after February 7, 2011, the developers are required to install street lights on all local residential streets which have street plans approved in accordance with Ordinance Chapter 13.10.050. Appropriate City staff shall have authority in determining the extent and phasing of street light construction, including the location of any applicable street light control centers that best fit into the overall master plan for future expansion of lighting circuits.
There are three main distinct scenarios identified in which street lights will be considered for installation. They are 1) streets with existing City-owned street lights, 2) streets that have streetlighting that was purchased from Kansas City Power and Light (KCP&L), and 3) new streets that are being constructed either through the City’s Capital Improvement Plan (CIP) or by developers.
Collector Streets with Existing KCP&L Streetlighting that was Purchased:
Collector Streets with Existing City-owned Streetlighting:
- Where street plans were approved prior to February 7, 2011, the City staff may initiate streetlighting requests for these types of streets via the City's Capital Improvements Program (CIP) which is reviewed and updated annually. Approved collector streetlighting projects are normally listed in the Budget.
New Collector Streets:
- Where street plans were approved on or after February 7, 2011, developers are required to install street lights on all such types of streets which have street plans approved in accordance with Ordinance Chapter 13.10.050. Appropriate City staff shall have authority in determining the extent and phasing of street light construction, including the location of any applicable street light control centers that best fits into the overall master plan for future expansion of lighting circuits.
There are two main distinct scenarios identified in which street lights will be considered for installation. They are 1) new City-owned street lights, and 2) streets that have streetlighting that was purchased from Kansas City Power and Light (KCP&L).
New Thoroughfare Streets:
- The City staff may initiate thoroughfare streetlighting requests for this type of street via the City's Capital Improvement Program. Approved primary thoroughfare streetlighting projects are normally listed in the Budget.
Thoroughfare Streets with Existing KCP&L Streetlighting that was Purchased:
Before initiating the design of a streetlighting system, the designer should contact the City staff to discuss the specific design criteria for the project and determine the scope of the project. Decisions should be made in regard to the functional roadway classification and pedestrian conflict area as well as the type of equipment that will be used in the design. The following is a brief summary of general design considerations.
Establish the Lighting Design Criteria:
All streetlighting designs for collector and thoroughfare streets shall be done in accordance with the Continuous Streetlighting Design Criteria, as already discussed.
From the Design Criteria Table, select the row corresponding to the functional roadway classification (Major or Collector). Then select the row corresponding to the pedestrian conflict area (High, Medium or Low). Follow this row across the table to determine the maintained average luminance, average to minimum luminance uniformity ratio, maximum to minimum luminance uniformity ratio and veiling luminance ratio to be achieved in the design.
Before any design is initiated, the designer should discuss the functional roadway classification and the pedestrian conflict area classification with City staff. The pedestrian conflict area should be based on the City of Overland Park’s Future Development Master Plan and the functional roadway classification should be based on the City of Overland Park Official Street Map.
Design calculations, indicating the design pole spacing, should be submitted with supporting data to verify that the proper light levels have been achieved.
Light Loss Factor:
After the initial installation of the streetlighting system, the light output continues to decrease over time due to many external factors. The result of the time-dependent depreciation effects must be considered in the initial design. The lighting design is based on a specific lighting level that should always be maintained at the end of the maintenance period. Therefore, the initial lighting in the field will always be brighter than required.
The light loss factor (LLF) is a multiplying factor included in the calculations to account for factors which change in time after the initial installation of the streetlighting system. This factor is the product of many other individual factors such as the maintenance factor, lamp lumen depreciation, luminaire dirt depreciation, equipment factors, etc. The LLF is multiplied by the initial lumen rating of the light source to determine the number of maintained lumens in the design. The LLF that should be used for all high pressure sodium (HPS) City streetlighting systems is 0.81. The LLF that should be used for all LED City streetlighting systems is 0.91.
The luminaire selection should be based on the type of street as well as the ability to meet the lighting criteria and maximize the pole spacing. All luminaires used on collector streets and thoroughfare streets shall be LED cobrahead style as specified in the section “Approved Streetlighting Equipment”. All luminaires on residential streets shall still be high pressure sodium (HPS).
Luminaire Classifications for Collector and Thoroughfare Streets:
- In general LED luminaires are rated as Class A through Class D depending on their ability to light a particular type of roadway and cross section. An approximate comparison between the different classes of LED luminaires and HPS luminaires is as follows:
- Class A LED – approximately equivalent to a 400W HPS
- Class B LED – approximately equivalent to a 310W HPS
- Class C LED – approximately equivalent to a 250W HPS
- Class D LED – approximately equivalent to a 150W HPS
- All luminaires shall be from the City’s Approved Product List. One of the reasons the City has moved toward LED luminaires is to reduce the long term cost of electrical charges. Therefore, the lowest class of LED luminaire should be used in the design that satisfies the given lighting criteria. The designer should consult with the City’s project manager at the early stages in design to verify the proper fixture to use based on appropriate calculations
Luminaire for Residential Streets:
- All luminaires on residential streets shall be a post top mounted fixture with a 100W HPS lamp. The luminaire shall be from the City’s Approved Products List.
Pole locations will vary depending on the type of street. Residential streets, collector streets in residential neighborhoods, collector streets in commercial areas, undivided thoroughfare streets, and divided thoroughfare streets will all have different design challenges. In addition to the pole location criteria already discussed for residential streets, there are additional pole location preferences that should be kept in mind. Each of the pole location preferences will be further discussed as follows.
Pole Location Preferences on Residential Streets:
- Sidewalks are generally only constructed on one side of residential streets. Since the street lights do provide some residual benefit of lighting the sidewalk and enhance pedestrian safety, the first choice for locating the street light poles should be on the sidewalk side of the street.
- As long as there is a minimum of a 4’ grass parkway between the back of curb and the sidewalk, the poles should desirably be located in the grass parkway. The minimum distance from the back of curb to the center of the street light pole should be 3’. If a 3’ pole setback cannot be achieved, consideration should be made to move the sidewalk adjacent to the curb, at least near the vicinity of the pole, and locate the pole 1’ behind the sidewalk.
- If street light poles cannot be located on the sidewalk side due to storm drainage, utility conflicts or right-of-way considerations, the poles may be moved to the other side of the street. The 3’ minimum setback from the back of curb to the center of the pole should still be maintained.
- Poles located at the intersection of residential streets should desirably be placed so the light pole can be used to mount stop, yield and street name signs. That means that they should be installed as near to the location where a vehicle should stop while maintaining a minimum of 3’ setback from the back of curb.
- All poles installed in residential areas should ideally be located on or near property lines whenever possible. In the case of larger lots, poles cannot always be located on the property line. In these cases, in order not to exceed the maximum desired pole spacing, poles can be located within the lot. The designer should take care not to locate the pole in front of large windows of houses.
- Any pole located near a residential drive entrance should be located a minimum of 3’ from the edge of the drive or concrete wing. The designer should always be careful not to mount a pole in a location that could be in the path of an errant vehicle that may be backing out of the driveway. An example would be on a curved drive entrance.
- The designer should also coordinate the location of all poles with existing trees, such that the fixture does not extend into the tree canopy or such that the tree canopy does not block the light output from the fixture.
Pole Location Preferences on Collector Streets:
- Collector streets generally have sidewalks on both sides of the street and are typically undivided roadways. Poles should be located on one side of the street which has the least conflicts with utilities.
- As long as there is a minimum of a 4’ grass parkway between the back of curb and the sidewalk, the poles should desirably be located in the grass parkway. The minimum distance from the back of curb to the center of the street light pole should be 3’. If a 3’ pole setback cannot be achieved, consideration should be made to move the pole 1’ behind the sidewalk. Longer bracket arms can be used to accommodate poles located behind the sidewalk.
- Any pole located near a residential or commercial drive entrance should be located a minimum of 3’ from the edge of the drive or concrete wing. The designer should always be careful not to mount a pole in a location that could be in the path of an errant vehicle that may be backing out of the driveway. An example would be on a curved drive entrance.
- Occasionally collector streets will be constructed with a raised median the entire length or possibly on the approach of an intersection. Poles can be located within the median with luminaires mounted at 180 degrees to each other in order to provide lighting on each side of the median.
- Where collector streets are designed with more than two lanes, such as in commercial areas where the roadway widens out to include multiple through lanes and turn lanes, it may be necessary to light the street from both sides in order to achieve the required lighting criteria. The desired pole arrangement in this case would be staggered across the street.
Pole Location Preferences on Undivided Thoroughfare Streets:
- On undivided thoroughfare streets, the light poles will generally be located on one side of the roadway, usually due to overhead power lines on the other side. The side selected to locate the poles on should be based on conflicts with overhead and underground utilities. Where situations allow, consideration should be given to a staggered arrangement if that provides the best lighting.
- At approaches to intersections, where the roadway widens out to include turn lanes, it may be necessary to light the street from both sides in order to achieve the required lighting criteria. The desired pole arrangement in this case would be staggered across the street.
Pole Location Preferences on Divided Thoroughfare Streets:
- Street light poles with two luminaires oriented 180 degrees apart should be located in the center of raised medians in the case of divided thoroughfares. It is acceptable to locate street light poles in medians measuring a minimum of 4’ from back of curb to back of curb, since all poles will be mounted on breakaway supports.
- If the center median is depressed instead of raised, the poles should be located on the outside curb lines. The minimum distance from the back of curb to the center of the street light pole should be 3’. The arrangement of poles on the outside edges would preferably be staggered, but will vary depending on how wide the median is and how many lanes are in each direction.
- At approaches to intersections, where the roadway widens out to include multiple turn lanes, it may be necessary to light the street from both sides in order to achieve the required lighting criteria. The pole arrangement may be staggered to the median, opposite the median or staggered across the street, which ever provides the overall best lighting levels and pole spacing.
Overhead Utility Line Clearance Requirements:
Overhead power lines or lower hanging cable lines should not be in contact with street light poles or luminaires. A minimum of 3’ horizontal and vertical clearance shall be maintained from any non-electric lines such as cable TV lines, aerial fiber lines, etc. Vertical and horizontal clearance to electric power lines shall be in accordance with KCP&L requirements and varies according to the line voltage. For lower voltage lines, the vertical and horizontal clearance should be in accordance with KCP&L Code Requirements DWG 130.1-12. The designer shall be responsible to determine if adequate clearance can be achieved and make adjustments to the pole locations or coordinate utility relocation if necessary. Whenever the vertical or horizontal distance from the nearest line to the pole or luminaire is less than 10’, KCP&L requires the line to be sleeved temporarily during the pole erection. The contractor will be required to contact KCP&L and coordinate the time the sleeves are necessary and to pay KCP&L a fee for their services.
Conduit Location Preferences:
On residential and collector streetlighting designs or undivided thoroughfare designs, it is desirable to run the electrical conduit in a straight line from pole to pole or pole to junction box. Desirably, the conduit should be located in the grass parkway between the back of curb and the sidewalk. In case of conflicts, the conduit may be located under the sidewalk as long as the conduit sweeps out from underneath the sidewalk to enter junction boxes and poles. Conduit installed parallel to the street should not be installed under the roadway or curb. Conduit should be installed under the street only when crossing from one side to the other.
On divided thoroughfare projects, where poles are located in the medians, the conduit location depends on the width of the median and whether the median consists of a concrete base with brick pavers or if the median consists of grass and/or landscaping. The design layout should indicate which of the “Miscellaneous Conduit Details” applies to each street light pole. The various “Miscellaneous Conduit Details” are shown on the General Notes and Legend Sheet in the Standard Details. Theses details should be consulted while reviewing the following discussion which outlines both situations.
Brick Paver Medians:
- When the median is a concrete base with brick pavers, the conduit should be installed near the centerline of the median and run in a straight line from pole to pole. At intersections, conduit runs from median nose to median nose should be offset slightly so it is not directly under the proposed object marker sign post that will be located directly behind the concrete median nose. This allows the sign post to be driven into the ground at the correct location without damaging the conduit.
Grass or Landscaped Medians:
- When the median consists of grass or landscaping, the conduit should be shown to be installed 3’ behind the median curb and swept into the center of the median at each street light pole location. This allows the median to be landscaped between street light poles without the danger of cutting the conduit or cable in the future. Conduit runs from median nose to median nose should be offset slightly so it is not directly under the proposed object marker sign post that will be located directly behind the concrete median nose. This allows the sign post to be driven into the ground at the correct location without damaging the conduit.
- Conduit crossing the header between brick paver medians and grass medians should transition from the center of the median under the brick pavers, to within 3’ from the back of the median curb.
Coordination with Traffic Signals at Intersections:
- At signalized intersections, the streetlighting conduit should tie into the traffic signal service box located near the median nose. The streetlighting cable should be located in the traffic signal conduit runs around the intersection instead of continuing directly from median nose to median nose through the center of the intersection.
Junction Box Locations:
Junction boxes should be installed whenever a branch circuit enters the main circuit. The junction box is used as a splice point for the cables that control the same circuit, as a future splice point for a branch circuit, or a pass through to facilitate ease of cable pulling. The following conditions in which junction boxes should be installed are described in more detail below.
Proposed or Future Branch Circuit at Intersections:
- Junction boxes are not required on both sides of a street crossing. The junction box should only be installed on one corner to provide an opportunity to tie into a branch circuit either in conjunction with the current plan or in the future. The junction box should be installed on the corner in which the street light circuit on the side street will most likely be installed. See the following illustration.
Median Noses at Divided Thoroughfare Street Intersections:
- Junction boxes should be installed in each median nose on thoroughfare street intersections where the streetlighting conduit runs from median nose to median nose. This would not apply to signalized intersections. In the case of a signalized intersection, there would most likely be a traffic signal service box located in the median. The streetlighting cable should be installed in the traffic signal conduit. The streetlighting conduit would be terminated at the service box.
Connecting into Existing Circuits:
- Junction boxes should be used to tie into an existing circuit when it is not feasible to extend the proposed conduit to the next street light pole. This may happen at the boundary of a construction project. In those cases, the existing streetlighting cable should be field located during construction and a junction box should be installed over the top. The cable splice from new to existing should be accomplished in the junction box.
At the End of Platted Streets Between Building Phases:
- Many times on developer constructed projects, the last streetlight pole does not end up at the end of the street section. In these cases, it is acceptable to install a Type 1 junction box at the end of the street so the conduit can be easily extended on the next building phase. Care should be taken to prevent the proliferation of junction boxes. The designer should plan accordingly to eliminate junction boxes whenever possible.
Streetlight Control Centers:
Streetlight control centers are pre-wired cabinets with relays, breakers, etc. that control when the steetlights receive electricity based on built-in photo controls. Each control center will require a photo cell to energize the streetlighting circuits. Power is provided to the individual street light poles only when it is dark enough to close the contact in the photo cell. Otherwise, there is no power in the system. This is a safety feature so any excavation work that cuts the cable during daylight hours will not be posed with live electrical power.
The normal design is a four circuit control center. Many times a 4-circuit controller will never control more than two or three circuits. However, every attempt should be made to locate it such that the number of circuits on one control center can be maximized.
Upon the approval of the project manager, a 1-circuit control center may be used. A 1-circuit control center may be applicable as a temporary installation between two building phases where the development master plan indicates that a new control center will be installed in subsequent development phases that will ultimate assume the load. There may also be applications in isolated areas, where it may make sense to install a single circuit controller where there is no possible way to connect to an existing streetlighting circuit or control center. One example is along the border between Overland Park and another city, where a cul-de-sac street extends into a neighborhood from the thoroughfare street. The City staff has the ultimate authority to approve or deny the use of a single circuit control center.
Streetlight Control Center Locations:
- Street light control center locations are subject to provisions in City Ordinance ZRR-2626, which is an ordinance relating to the Unified Development Ordinance for the City of Overland Park, Kansas; amending and repealing existing Overland Park Municipal Code Sections 18.180.070, 18.250.050 and 18.410.110. A summary of the ordinance outlining the requirements for street light control centers and the application to street light control centers is provided, herein. The preferred location in order of priority is modified to apply to current practice in the case of street light control centers.
Utility Structure Ordinance:
- Any structure located within the public right-of-way shall be located behind the sidewalk and is subject to approval by the City Engineer. When placing utility structures, priority shall be given to finding available utility easements or right-of-way in preferred locations. Preferred locations, as listed in order of priority, are: 1) properties developed with non-residential uses; 2) thoroughfare landscape/utility easements; 3) street side yards on a corner lot behind the front yard setback; and 4) front yards within the required side yard setback. Proper utility easements or streetlight easements shall be acquired if the controller is to be located outside of the right-of-way.
Outside of Intersection Sight Distance Triangles:
- Street light control centers should not be located within the intersection sight distance triangle as defined by A Policy on Geometric Design of Highways and Streets by the American Association of State Highway and Transportation Officials (AASHTO), latest edition.
Proximity to Power Source:
- The street light control center needs to be located within close proximity to the KCP&L power source, whether it is a power pole with a transformer or a ground mounted transformer. KCP&L requires that the distance from the control center to a pole mounted transformer cannot exceed 150’. The distance from the control center to a ground mounted transformer cannot exceed 200’.
Maximizing Control Center Circuits:
- Street light control centers have the capacity to operate four independent circuits and should be located such that the number of circuits utilized can be maximized. Ideal locations would be at a 4-leg intersection where one circuit can extend in all the four cardinal directions or at 3-leg intersections where at least three circuits can be utilized.
- There will be situations where the voltage drop becomes too great between intersections and a controller has to be located mid-block which will only utilize two circuits. Before arbitrarily determining to install a mid-block circuit, the designer should evaluate all possible alternatives, including the extension of existing circuits on the side streets from existing control centers within the development.
- The designer, with the help of the City staff, should evaluate all existing control centers in the vicinity of the project to determine if there are any underutilized controllers that can be relocated to a better location and could still be used to back-feed the existing street lights. The ultimate goal is to reduce the number of control centers in an area by placing them or relocating them in a more strategic location. This may require some off-site construction work to accommodate.
Control Center Orientation:
- Street light control centers shall be oriented such that the photocell always faces to the north or to the east. The plan symbol for the control center shows a concrete pad which always indicates the front side of the cabinet. As you would stand on the pad facing the front of the control center, the photocell is always located on the right hand side of the cabinet. The shaded portion of the triangle in the symbol represents the photocell.
Circuit Numbering Convention
- Circuit numbers will be identified by the principal direction the circuit extends. There are times, especially on residential streets, where the circuit extends in many directions. The principal direction should follow the numbering as listed below.
- Circuit number 1 shall always be to the north
- Circuit number 2 shall always be to the east
- Circuit number 3 shall always be to the south
- Circuit number 4 shall always be to the west
- Exceptions are if modifying an existing control center which already is configured differently.
Connecting Proposed Electrical Cable into Existing Street Light Poles:
When extending proposed conduit into an existing street light pole foundation, several things should be considered in the design. If the pole is mounted to an existing screw-in foundation, the designer should verify with the City project manager that it is new enough to have two conduit entry holes. If it is an older foundation, it may only have one conduit entry. If the existing foundation is concrete, you will not be able to connect a new conduit to extend the circuit. In either the case of an old screw-in foundation with only one conduit entry or a concrete foundation, the designer will have to either install a junction box near the pole to intercept the existing cable/conduit, or replace the foundation with a new screw-in foundation. When connecting the proposed electrical cables to the existing electrical cables in the base of the pole, new fused and un-fused disconnects as well as new multi-tap electrical connectors shall be used. The existing fixture should also be shown to be re-lamped.
Luminaires Located on Combination Traffic Signal/Street Light Poles:
All luminaires mounted on combination traffic signal/street light poles at signalized intersections shall be connected to the streetlighting circuits controlled by the streetlighting control center instead of running off of the traffic signal control center.
Exceptions exist for isolated intersections where there are no surrounding street light control centers or streetlighting circuits. In such cases, the 3-1c #4 AWG USE streetlighting cables should be extended to the traffic signal control center for power. In addition, the designer should provide necessary notation to indicate that the multi-tap ballasts in any HPS luminaire should be wired for 120V. If the fixture is LED, the driver should not have to be modified. The luminaires should be equipped with photocells. A 15 amp circuit breaker should be called out to be installed in the secondary service pedestal to isolate the lighting circuit.
Requirements for House Addresses on Equipment:
Street light control centers and street light poles shall each be assigned a house address. The reasons for doing so and the procedures to accomplish each are discussed below:
House Addresses for Street Light Poles:
- House addresses are field stenciled on street light poles to help maintenance crews respond to lamp outages or maintenance issues when a citizen calls the situation in or if the maintenance crews are being dispatched to take care of a problem. It is a way to call-in and respond to specific problems and the address identifies the exact pole that requires attention.
- House addresses are only required for street light poles on collector or thoroughfare streets for poles providing 30’ and 40’ mounting heights. House addresses are not required for street lights on residential streets providing 15’ mounting heights, because the address on the house provides similar information.
- During the design, the City staff will provide the specific house numbers to the designer to add to the pole callout nomenclature. The standard practice is to assign an address at each end of the poles located at a median break or intersection. The two addresses are subtracted and the number is divided by one number less than the number of poles. The resulting number is then systematically added to the initial number, beginning with the smallest address and working toward the end. This establishes a uniform numbering system between the median breaks or intersections. Each address should be rounded to the closest numbered address. Pole addresses in a median should always be even numbers. Pole addresses on the side of the street shall have odd numbers if they are located on the south or east side of the street. Pole addresses shall have even numbers if they are located on the north or west side of the street. An example for a divided thoroughfare with the poles located in the center median follows:
- There is a median break on College Boulevard at King and Nieman Road. The 100 block for Nieman is 11100. The 100 block for King is 11300. A street light is located in the west median nose at Nieman and is assigned an address of 11108. Another street light is located in the east median nose at King and is assigned an address of 11294. Assume that there will be eight poles total between the two median noses.
- (11294 - 11108) = 26.6
- This is the number that should be added to the initial assigned pole address beginning at the smallest address.
- Therefore, the next pole west of Nieman should be (11108 + 26.6) = 11134.6 (Round the address to 11134).
- The next pole address would be 11134.6 + 26.6 = 11161.2 (Round the address to 11162).
- Continue adding 26.6 to all subsequent non-rounded addresses, and rounding to the nearest even number for each pole.
House Addresses for Street Light Control Centers:
- Each street light control center requires an electrical service address. City staff will provide the control center address to the designer after the designer determines the location and whether Kansas City Power and Light (KCP&L) can provide the necessary 240V power to the proposed location. KCP&L uses the address for billing electrical usage to the City. The City also uses the address to track invoices.
- Each address for the street light control center shall be followed with an “LC” extension which stands for “Lighting Controller”. The procedure for coordinating with KCP&L is addressed below in Section 1.8 “Coordinating Electrical Service with KCP&L”.
Showing House Addresses on the Plans:
- House addresses for the street light control center should be shown in the station and offset callout for the pole and also should be the first number designated in each pole callout. For example:
- 11302-1-4 (8',12") (11134)
- Sta 10+23.5, 30.2' Rt
- The 11302 represents the control center address; the 1 represents circuit number 1; and 4 represents the 4th pole on circuit number 1. The 8’ and 12’ represents the luminaire bracket arm length on the left side and the right side, respectively and the 11134 is the assigned house address for the pole.
- House addresses for each pole should be shown in parenthesis immediately behind the callout for the controller address, circuit number, pole number and arm length information according to the legend in the Standard Details.
- The street light control center address should also be shown in a box located in the bottom right hand portion of each plan sheet in which it applies. If poles connected to that control center appear on more than one sheet, the address should appear on the same sheets. If there are poles that are fed from different control centers on one sheet, each control center address should appear on the sheet. The general format of the note should be:
Proposed Street Light Control Center Electrical Service Address: 11302 LC College Blvd
- The existing address for each control center that is being removed or used in place should also be indicated in a boxed note, replacing “Proposed” with either “Remove” or “Existing”.
Coordinating Electrical Service with KCP&L:
The project manager or designer should perform the initial work to locate the streetlighting control center based on field conditions where there is an existing transformer. The street light control center needs to be located within close proximity to the KCP&L power source, whether it is a power pole with a transformer or a ground mounted transformer. In general, KCP&L requires that the distance from the control center to a pole mounted transformer cannot exceed 150’. The distance from the control center to a ground mounted transformer cannot exceed 200’.
KCP&L should be contacted, either verbally or in writing, to verify if power can be obtained at a particular location before a lot of design work is completed. In either case, it is beneficial to send them a plan sheet or meet them in the field. When requesting power, ask if there will be a charge to obtain power at the desired location. KCP&L can generally provide power anywhere, but there may be a significant cost to do so. Ask if there is a better location where they have an existing transformer or sectionalizer that would be better or cheaper to acquire power from. If the control center can be relocated to a better position, make the design change. If not, ask KCP&L to provide an estimate to the City for the cost associated with obtaining power before the design is finalized.
The designer should provide the City a copy of all letter correspondence or email correspondence to KCP&L to insure the necessary procedures are being performed. After KCP&L has agreed to a preliminary power source and location, the project manager or designer should prepare a preliminary plan sheet showing the location of the power pole and the location of the control center with conduit and notes indicating the location where power will be obtained. After the power location has been established, the project manager will then assign an electrical service address to each control center as outlined in the document “Procedure for Assigning an Electrical Service Address to a Streetlighting Controller or Traffic Signal Controller and Acquiring Power on Site”.
Removal of Existing Street Lights:
All existing street lights that will be removed shall be identified on the plan sheets. The exact procedure varies depending on whether the existing street lights are the ones that were purchased from KCP&L or if they are existing lights that were installed per the City of Overland Park standard details. The procedures for both are explained below:
Removal of Existing City Owned Street Lights Installed per Overland Park Standard Details:
- All existing City owned street lights shall be shown on the plans. Any existing street lights that will not be re-used in the final design shall be indicated to be removed by a construction note. The note should include the removal of the pole, luminaire, arm and screw-in foundation. Existing concrete pole foundations should be shown to be removed to a depth of at least 24”. All conduit and cable can be abandoned in place or can be removed at the option of the contractor if it is in conflict with other construction items.
Removal of Existing Street Lights Purchased from KCP&L:
- All existing street lights shall be shown on the plans. The City will determine which lights should be designated to be removed. The designer shall indicate any pole not to be re-used as “Existing Street Light to be Removed by Others”. The City of Overland Park or their on-call representative will remove the poles and not the project contractor.
- Each pole purchased from KCP&L has a PK number designated with a sticker, such as PK-1423. The designer should indicate the proper PK number on the plans next to the pole.
- City staff will coordinate with their on-call representative for the removal of the lights following the operating procedure established by the City. The process involves writing the on-call representative to provide them a list of poles that are scheduled to be removed. The on-call representative will submit a cost estimate to perform the work which needs to be approved by the Director of Public Works. After approval, the project manager will coordinate the removal with the on-call representative and notify in an attempt to keep the lights operational as long as possible before being removed. A letter will then be sent to KCP&L instructing them to remove the lights from their database and revise their monthly billing. (See the Streetlight Removal Procedure for removal of streetlights that were purchased from KCP&L)
Voltage Drop Calculations:
Voltage drop is an important factor in determining how many luminaires can be placed on any circuit. The voltage drop in any electrical circuit is directly dependent upon current and wire resistance.
Permissible Voltage Drop:
- The permissible voltage drop is the allowable voltage drop across an entire circuit of a specific system voltage. This is generally limited to what the fixture can handle.
- With the constant wattage ballast, the permissible voltage drop is five percent of the system voltage. A factor of 0.95 is to be applied to the system voltage to allow for line fluctuations. This results in an allowable drop of 11.4 volts for a 240-volt circuit.
- Perm Voltage Drop = System Voltage x 5% Drop x 0.95 line fluctuation factor
- = 240 x 0.05 x 0.95
- = 11.4 volts
HPS Fixture Operating Current:
- Operating current is determined using 95 percent of the system voltage to allow for line fluctuations. In addition, the lamp wattage is increased by a factor of 1.3 to allow for ballast load. The formula for power is P = V x I and the formula for current is I = P / V.
- The operating amps for each luminaire are based on the wattage of the lamp used.
- Operating Amps = 1.3 x Wattage
- Voltage x Line Fluctuation Factor
- Operating Amps = 1.3 x Wattage
- 240 x 0.95
- The following operating amps should be used in the design calculations for HPS fixtures:
HPS Fixture Operating Amps 100 Watt 150 Watt 250 Watt 400 Watt 0.5 Amps 0.9 Amps 1.4 Amps 2.3 Amps
LED Fixture Operating Current:
- Operating current is determined using 95 percent of the system voltage to allow for line fluctuations. Since LED fixtures have a driver instead of a ballast, there is no multiplier for ballast loss. The formula for power is P = V x I and the formula for current is I = P / V.
- The operating amps for each luminaire are based on the wattage of the lamp used.
- Operating Amps = Wattage
- Voltage x Line Fluctuation Factor
- Operating Amps = Wattage
- 240 x 0.95
- LED fixtures in the same class have different wattages based on the manufacturer. The values shown in the following table are based on the worse case scenario for approved LED fixtures in each luminaire classification and should therefore be used in the voltage drop calculations:
LED Fixture Operating Amps Class A Class B Class C Class D 0.9 Amps 0.77 Amps 0.58 Amps 0.32 Amps
Cable Circular Mils:
- A circular mil is a unit of area used when denoting the cross sectional area of a wire or cable.
- 1 mil = 0.001 inch
- To convert the diameter of a wire to mils: mil = d x 1,000
- Example: #4 AWG wire has a diameter of 0.2043037 inches.
- 0.2043037 inches x 1,000 = 204.3037 or 204 mils
- CM = mil2
- Example: Circular mils of #4 AWG wire
- CM = (204.3037 mils)2
- CM = 41,740
Calculating Voltage Drop:
- According to Ohm's Law the voltage drop in a line is equal to the current in amperes multiplied by the resistance of the line in ohms:
- E = I x R
- E = voltage
- I = Current (in amperes)
- R = Resistance (in ohms)
- Since the resistance of a wire conductor is inversely proportional to the cross-sectional area of the wire, increased voltage drops are developed as the wire diameters decrease. The areas of wires in circular mils and the resistance in ohms per 1000 feet that should be used in calculations are shown below for #4 AWG copper cable.
Properties of Stranded Copper Conductors Cable Size (AWG) Area
4 41,740 0.310
- The voltage drop in any line is calculated from the formula:
- Voltage Drop = 2 x K x Q x I x D
- K = Direct Current Constant (for copper, K = 12.9 ohms)
- Q = Aternating Current Adjustment Factor (Q = 1, for all wire less than 2/0 wire)
- I = Load, in Ampers
- D = Distance from the power supply, in feet
- CM = Cross sectional area of cable, in Circular Mills
- Voltage Drop = 2 x 12.9 x 1.0 x Operating Amps x Distance
- We add 5% is added to the center to center distance to allow for snaking of the conduit and cable.
- Operating amps = the operating amps of one fixture times the number of fixtures at the point of calculation. Transposing this formula, the required area in circular mils can be computed:
- Area (circular mils) = 25.8 x Operating Amps x No. of Lamps x 1.05 x Distance
- Permissible Voltage Drop
- Calculate the circular mils between every fixture in the circuit and add the total number of circular mils to get the total circular mils. Verify that this is less than the circular mils for a #4 AWG cable.
- The voltage drop should then be checked using the following equation:
- Voltage Drop = 2 x L x I x R as follows:
- Voltage Drop = 2 x Distance x Current x Resistance ÷1,000
- L = Distance between lights. Use 1.05 x distance (5% to allow for snaking)
- I = Current = operating amps x number of lamps
- R = Resistance of cable per 1,000 feet = 0.31 (From above Table, the resistance of #4 AWG wire in ohms/1,000 ft)
- If circuit loading or voltage drop requires a larger wire size than a #4 AWG then one or more of the following can be considered:
- Locate the control center closer to the lighting system
- Install additional control centers
- Note that long runs of parallel circuits should be avoided unless otherwise approved
- Example to Determine Necessary Wire Cable Size:
- Given: Five 250-watt HPS lamps on a 240-volt circuit spaced at 200, 425, 615, 815 and 1,030 feet respectively, from the control center. There must be sufficient current to operate the first lamp as well as the next four lamps.
- 1.05 x 200 ft x 1.4 amps x 5 lamps x 25.8/11.4 = 3,327 cir. mils to 1st lamp
- 1.05 x 225 ft x 1.4 amps x 4 lamps x 25.8/11.4 = 2,994 cir. mils to 2nd lamp
- 1.05 x 190 ft x 1.4 amps x 3 lamps x 25.8/11.4 = 1,896 cir. mils to 3rd lamp
- 1.05 x 200 ft x 1.4 amps x 2 lamps x 25.8/11.4 = 1,331 cir. mils to 4th lamp
- 1.05 x 215 ft x 1.4 amps x 1 lamp x 25.8/11.4 = 715 cir. mils to 5th lamp
- Total Area = 10,263 cir. mils.
- The calculated circular mils is less than the capacity of a #4 AWG wire (41,740 as shown in the above Table. This calculation will need to be made for each circuit at each street light control center.
- The voltage drop should then be checked using E = I x R as follows:
- Voltage Drop = 2 x Distance x Current x Resistance ÷1,000
- Voltage Drop = 2 x Distance x Operating Amps x No. of lamps x Resistance÷1,000
- 2 x 1.05 x 200 ft x 1.4 amps x 5 lamps x 0.31 ohms/1,000 ft = 0.91 volt drop to 1st lamp
- 2 x 1.05 x 225 ft x 1.4 amps x 4 lamps x 0.31 ohms/1,000 ft = 0.82 volt drop to 2nd lamp
- 2 x 1.05 x 190 ft x 1.4 amps x 3 lamps x 0.31 ohms/1,000 ft = 0.52 volt drop to 3rd lamp
- 2 x 1.05 x 200 ft x 1.4 amps x 2 lamps x 0.31 ohms/1,000 ft = 0.36 volt drop to 4th lamp
- 2 x 1.05 x 215 ft x 1.4 amps x 1 lamp x 0.31 ohms/1,000 ft = 0.20 volt drop to 5th lamp
- Total Drop = 2.81 volts
- 2.81 volts/(240 volts x .95) = 1.23% which is less than 5%. Therefore it is acceptable
Calculating Circuit Breaker Ratings:
- Circuit breakers are protective devices for over-current conditions. When the current passing through the circuit breaker exceeds a predetermined amount, the breaker trips and opens the faulty circuit. The amount of current required to operate the trip mechanism is referred to as the "trip rating". Proper protection of the circuit requires a breaker with the correct "tripping" current value. This value, "trip rating", can be readily computed by totaling the number of luminaires for each circuit breaker and thereby obtaining the total current being used in the circuit. To prevent unnecessary tripping of the breaker during surges and in-rush currents, the total current is usually multiplied by a factor of 1.3.
- Example:Using the previous example: 5 each - 250-watt luminaires require a normal operating current of 5 x 1.4 amps = 7 amps
- The line loss load in amperes is added as follows:
- 14.5 watts/(240 volts x 0.95) + 7 amps = 7.1 amps
- The Trip rating = 7.1 amps x (1.3) = 9.2 amps.
- The street light controller is equipped with standard 30 amp circuit breakers. The circuit breakers can be increased to a 40 amp breaker under heavier loads. For the above example, a 30-amp breaker is more than sufficient.
Approved Streetlighting Equipment:
The following equipment has been approved for all City-owned streetlighting systems. The following information is provided as a general discussion only and the designer is responsible to review the standard details in the selection of equipment for the streetlighting system.
The type of pole used is based on the classification of street it will be located on. Poles and mounting heights will vary depending on if it is a residential street, collector street or thoroughfare street.
- Poles for residential streets shall be round, tapered aluminum poles for 15-foot mounting heights.
- Poles for collector streets shall be round, tapered aluminum poles for 30-foot mounting heights.
- Poles for thoroughfare streets shall be round, tapered aluminum poles for 40-foot mounting heights.
Luminaire Bracket Arms:
For conventional lighting systems, there are several different arm lengths and styles of arms that are used. The various styles and lengths and the appropriate uses for each are summarized below.
Type A luminaire bracket arms consist of a single member arm. Type A arms are used when the length is less than 10’. An exception to this is in applications where one pole has two arms, regardless of the orientation. If one arm is required to be a Type B style, the other arm should also be a Type B style to provide a consistent look, even if the arm is less than 10’ in length.
Type B luminaire bracket arms consist of a two member truss arm design. Type B arms are used when the length is 10’ or greater.
The length of the bracket arm is dependant upon many factors such as street width, pole location in relation to the curb and the presence of a median. Typical preferences are provided as follows, but the selection of an arm length should be used that enables the designer to achieve the required lighting criteria. Single member bracket arms are available in 6’ and 8’ lengths. Twin member bracket arms are available in 10’, 12’ and 15’ lengths. Only bracket arms of these lengths are used.
18.104.22.168. Collector Streets (30’ Mounting Heights): On typical collector streets that are 36’ wide from back-of-curb to back-of-curb, either a 6’ or 8’ arm is used. Depending on whether the pole is located behind the sidewalk or in the grass parkway between the sidewalk and the curb, or where the street width becomes wider, such as the approaches to an intersection where additional turn lanes are added, the arm length may need to be increased to 12’ in order to achieve the required lighting criteria.
22.214.171.124. Undivided Thoroughfare Streets (40’ Mounting Heights): On an undivided thoroughfare street, generally 6’, 8’ or 12’ arms are used unless the poles need to be offset farther behind the sidewalk due to utility conflicts or where the street width becomes wider, such as the approaches to an intersection where additional turn lanes are added.
126.96.36.199. Divided Thoroughfare Streets (40’ Mounting Heights): Divided thoroughfares typically have a 24’ wide center median to divide opposing lanes of traffic. On divided thoroughfare streets where the light poles are installed in a raised median, there are a few different arm configurations that are used. In sections where there are no left turn lanes and the median is only separating through lanes of traffic, two 12’ arms are used oriented 180 degrees apart.