北美道路照明标准.pdf

22Roadway Lighting Fixed lighting of public ways for both vehicles and pedestrians can create a nighttime environment in which people can see comfortably and can quickly and accurately identify objects on the roadway being traveled.Roadway lighting can improve traffic safety,achieve efficient traffic movement,and promote the general use of the facility during darkness and under a wide variety of weather conditions.As a supplement to vehicular headlight illumination,fixed lighting can enable the motorist to see details more distinctly,locate them with greater certainty,and react safely to roadway and traffic conditions present on or near the roadway facility.Pedestrians must be able to see with sufficient detail to readily negotiate the pedestrian facility and recognize the presence of other pedestrians,vehicles,and objects in their vicinity.When fixed-lighting principles and techniques are properly applied,the visibility provided on these public ways can provide economic and social benefits to the public,including:?Reduction in nighttime accidents?Aid to police protection?Facilitation of traffic flow?Promotion of business and industry during nighttime hours?Inspiration for community spirit and growth This chapter considers only fixed lighting for the different kinds of public roads,pedestrian walkways and bikeways of a quality considered appropriate to modern requirements for night use.See Chapter 23,Transportation Lighting,for information on vehicle headlighting.CLASSIFICATION DEFINITIONS1 Roadway:Pedestrian Walkway and Bikeway Classifications Freeway.A divided major roadway with full control of access and with no crossings at grade.This definition applies to toll as well as nontoll roads as follows:Freeway A.Roadways with visual complexity and high traffic volumes.Usually this type of freeway is found in major metropolitan areas in or near the central core and operates through much of the early evening hours of darkness at or near design capacity.Freeway B.All other divided roadways with full control of access where lighting is needed.Expressway.A divided major roadway for through traffic with partial control of access and generally with interchanges at major crossroads.Expressways for noncommercial traffic within park areas are generally known as parkways.Major.The part of the roadway system that serves as the principal network for through traffic flow.The routes connect areas of principal traffic generation and important rural highways entering the city.Collector.The roadways serving traffic between major and local roadways.These are roadways used mainly for traffic movements within residential,commercial,and industrial areas.Local.Roadways used primarily for direct access to residential,commercial,industrial,or other abutting property.They do not include roadways carrying through traffic.Long local roadways are generally divided into short sections by a system of collector roadway systems.Alley.Narrow public ways within a block,generally used for vehicular access to the rear of abutting properties.Sidewalk.Paved or otherwise improved areas for pedestrian use,located within public street rights-of-way that also contain roadways for vehicular traffic.Pedestrian Walkway.A public walk for pedestrian traffic,not necessarily within the right-of-way for a vehicular traffic roadway.Included are skywalks(pedestrian overpasses),subwalks(pedestrian tunnels),walkways giving access to parks or block interiors,and midblock street crossings.Isolated Interchange.A grade-separated roadway crossing that is not part of a continuously lighted system,with one or more ramp connections with the crossroad.Isolated Intersection.The general area where two or more discontinuously lighted roadways join or cross at the same level.The intersection includes the roadway and roadside facilities for traffic movement in that area.A special type is the channelized intersection,in which traffic is directed into definite paths by islands with raised curbing.Bikeway.Any road,street,path,or way that is specifically designated as being open to bicycle travel,regardless of whether such facilities are designed for the exclusive use of bicycles or are to be shared with other transportation modes.Type A:Designated bicycle lane.A portion of roadway or shoulder that has been designated for use by bicyclists.It is distinguished from the portion of the roadway for motor vehicle traffic by a paint stripe,curb,or other similar device.Type B:Bicycle trail.A separate trail or path from which motor vehicles are prohibited and which is for the exclusive use of bicyclists or the shared use of bicyclists and pedestrians.Where such a trail or path forms a part of a highway,it is separated from the roadways for motor vehicle traffic by an open space or barrier.Area Classifications(Abutting Land Uses)Certain land uses,such as office and industrial parks,may fit into any of the classifications below.The classification selected should be consistent with the expected night pedestrian activity.Commercial.A business area of a municipality where ordinarily there are many pedestrians during night hours.This definition applies to densely developed business areas outside,as well as within,the central part of a municipality.The area contains land use that frequently attracts a heavy volume of nighttime vehicular and pedestrian traffic.Intermediate.Those areas of a municipality characterized by frequent moderately heavy nighttime pedestrian activity,as in blocks having libraries,community recreation centers,large apartment buildings,industrial buildings,or neighborhood retail stores.Residential.A residential development,or a mixture of residential and small commercial establishments,characterized by few pedestrians at night.This definition includes areas with single-family homes,town houses,and small apartment buildings.Pavement Classifications The calculation of pavement luminance requires information about the surface reflectance characteristics of the pavement.Studies have shown that most common pavements can be grouped into a limited number of standard road surfaces having specified reflectance data given by reduced luminance coefficient tables(r tables).In this section,pavement reflectance characteristics follow the established CIE document.2 A description of road surface classifications is given in Figure 22-1.The r tables quantifying the pavement class are shown in Figure 22-2.Figure 22-1.Road Surface Classifications Figure 22-2.Continued.Figure 22-2e.Continued Figure 22-2.The r-Tables for Standard Surfaces:(a)R1,(b)R2,(c)R3,(d)R4.All values must be multiplied by 10,000.Angles are shown in(e).(Adapted from reference 2.)Luminaire Light Distribution Classifications Proper distribution of the light flux from luminaires is one of the essential factors in efficient roadway lighting.The light emanating from the luminaires is directionally controlled and proportioned in accordance with the roadway width,the spacing between luminaires,and the mounting locations where the luminaires are expected to be used.Therefore,there is a need for a luminaire light distribution classification system to aid the engineer or designer to narrow down the selection of luminaires that might meet the requirements specified for a given roadway system.Several methods have been devised for showing the light distribution pattern from a luminaire(Figures 22-3 through 22-7).For practical operating reasons,the range in luminaire mounting heights may be limited.Therefore,it becomes necessary to have several different light distributions in order to light different roadway widths effectively,while using various luminaire spacing distances at a fixed luminaire mounting height.All luminaires can be classified according to their lateral and vertical distribution patterns.Different lateral distributions are available for different ratios of street width to mounting height.Different vertical distributions are available for different ratios of spacing to mounting height.Distributions with higher vertical angles of maximum intensity emission are necessary to obtain the required uniformity of illuminance where longer luminaire spacings are used(as on residential and light-traffic roadways).These higher vertical emission angles produce a more favorable pavement luminance,which may be desired for silhouette seeing where the traffic volume is low.Distributions with lower vertical angles of maximum intensity emission are used in order to reduce system glare.This becomes more important when using high-lumen-output lamps.The lower the emission angle,the closer the luminaire spacing must be to obtain required illuminance uniformity.Luminaire light distribution may be classified in respect to three criteria:?Vertical light distribution?Lateral light distribution?Control of light distribution above maximum intensity Classification of the light distribution should be made on the basis of an isointensity diagram which,on its rectangular coordinate grid,has superimposed a series of longitudinal roadway lines(LRL)in multiples of the mounting height(MH),and a series of transverse roadway lines(TRL),also in multiples of the MH.The relationship of LRL and TRL to an actual street and the representations are shown in Figures 22-3 through 22-7.The minimum information that should appear on such an isointensity diagram for classification is as follows:Figure 22-3.Recommended vertical light distribution boundaries on rectangular coordinate grid(representation of a sphere).Lines a and b are isointensity traces.1.LRL lines at 1.0,1.75,and 2.75 MH 2.TRL lines at 1.0,2.25,3.75,6.0,and 8.0 MH 3.Maximum-intensity location and half-maximum-intensity trace 4.Intensity lines at the numerical values of 2.5,5,10,and 20%of the rated bare lamp lumens Following are several types of luminaire light distributions.Other variations from these distributions may be useful for special applications.Vertical Light Distributions.Vertical light distributions are divided into three groups:short(S),medium(M),and long(L)(Figures 22-3 and 22-6).Short Distribution.A luminaire is classified as having a short light distribution when its maximum-intensity point lies in the S zone of the grid,which is from the 1.0-MH TRL up to the 2.25-MH TRL.The maximum luminaire spacing is generally less than 4.5 times the mounting height(Figures 22-3 and 22-4).Medium Distribution.A luminaire is classified as having a medium light distribution when its maximum-intensity point lies in the M zone of the grid,which is from the 2.25-MH TRL up to the 3.75-MH TRL.The maximum luminaire spacing is less than 7.5 times the mounting height(Figures 22-3 and 22-4).Long Distribution:A luminaire is classified as having a long light distribution when its maximum-intensity point lies in the L zone of the grid,which is from the 3.75-MH TRL up to the 6.0-MH TRL.The maximum luminaire spacing is less than 12 times the mounting height(Figures 22-3 and 22-4).Figure 22-4.Typical lighting layouts showing spacing-to-mounting height relationships and terminology with respect to luminaire arrangement and spacing.Short Distribution-for luminaires designed to be located less than 4.5 MH between luminaires.Medium Distribution-for luminaires designed to be located in the range of 4.5 MH to 7.5 MH between luminaires.Long Distribution-for luminaires designed to be located in the range of 7.5 MH to 12 MH between luminaires.Figure 22-5.Recommended lateral light distribution boundaries on a rectangular coordinate grid(representation of a sphere).Some information omitted for clarity.See Figure 22-3 for a complete diagram.Lateral Light Distributions.Lateral light distributions(Figures 22-5 and 22-6)are divided into two groups based on the location of the luminaire in relation to the area to be lighted.Each group may be subdivided into divisions with regard to the width of the area to be lighted in terms of the MH ratio.Only the segments of the half-maximum-intensity isointensity trace that fall within the longitudinal distribution range,as determined by the point of maximum intensity(S,M,or L),are used for establishing the luminaire distribution width classification.Luminaires At or Near Center of Area.The group of lateral width classifications that deals with luminaires intended to be mounted at or near the center of the area to be lighted has similar light distributions on both the house side and the street side of the reference line.Type I.A distribution is classified as Type I when its half-maximum-intensity isointensity trace lies within the Type I width range on both sides of the reference line which is bounded by 1.0-MH house side LRL and 1.0-MH street side LRL within the longitudinal distribution range(S,M,or L)where the point of maximum intensity falls(Figure 22-6a).Type I Four-way.A distribution is classified as a Type I four-way when it has four beams of the width as defined for Type I above(Figure 22-6b).Type V.A distribution is classified as Type V when it has circular symmetry,being essentially the same at all lateral angles around the luminaire(Figure 22-6c).Luminaires Near Side of Area.The lateral width classifications that deal with luminaires intended to be mounted near the side of the area to be lighted vary as to the width of distribution range on the street side of the reference line.The house side segment of the half-maximum-intensity isointensity trace within the longitudinal range in which the point of maximum intensity falls(S,M,or L)may or may not cross the reference line.In general it is preferable that the half-maximum-intensity isointensity trace remain near the reference line.The variable width on the street side is as defined by the following.Type II.A distribution is classified as Type II when the street side segment of the half-maximum-intensity isointensity trace within the longitudinal range in which the point of maximum intensity falls(S,M,or L)does not cross the 1.75-MH street side LRL(Figure 22-6d).Type II Four-way.A distribution is classified as a Type II four-way when it has four beams,each of the width on the street side as defined for Type II above(Figure 22-6e).Type III.A distribution is classified as Type III when the street side segment of the half-maximum-intensity isointensity trace within the longitudinal range in which the point of maximum intensity falls(S,M,or L)lies partly or entirely beyond the 1.75-MH street side LRL,but does not cross the 2.75-MH street side LRL(Figure 22-6f).Type IV.A distribution is classified as Type IV when the street side segment of the half-maximum-intensity isointensity trace within the longitudinal range in which the point of maximum intensity falls(S,M,or L)lies partly or entirely beyond the 2.75-MH street side LRL(Figure 22-6g).Figure 22-6.Plan view of roadway coverage for different types of luminaires.Control of Distribution Above Maximum Intensity.Although the pavement luminance generally increases on increasing the vertical angle of light