FHWA Lighting Handbook

August 2012
TECHNICAL REPORT DOCUMENTATION PAGE.

1. Report No.: 2. Government Accession No.: 3. Recipient's Catalog No.:

4. Title and Subtitle: 5. Report Date:

 FHWA Lighting Handbook

August 2012

6. Performing Organization Code:

HSA

7. Author(s):

Paul Lutkevich, Don McLean, Joseph Cheung

8. Performing Organization Report 

No.:

9. Performing Organization Name and Address: 10. Work Unit No.:

Parsons Brinckerhoff, 75 Arlington St. Boston, MA 11. Contract or Grant No.:

DTFH 61-10-P-00162

12. Sponsoring Agency Name and Address: 13. Type of Report and Period 

Covered:

Office of Safety

Federal Highway Administration

1200 New Jersey Ave. SE

Washington DC 20590

Final Report.

14. Sponsoring Agency Code:

15. Supplementary Notes:

16. Abstract:

This handbook is an update to the 1978 FHWA Lighting Handbook 78-15 as well as the 1983 addendum. It 

is meant to provide guidance to designers and State, city, and town officials concerning the application of 

roadway lighting. Supplementing and referring to other resources developed by AASHTO, IES, and CIE 

this document contains information on:

Policy and Guidance – discussing references, policy, and recommendations used by FHWA in evaluating 

and administering funds for roadway and street lighting projects.

Basic Terms and Concepts – discussing descriptions of significant terms and concepts used in roadway and 

street lighting projects.

Warranting Criteria – including various warranting methods available when considering lighting.

Lighting Impacts – discussing various impacts (both positive and negative) of lighting systems and ways to 

control and mitigate.

Application Considerations – supplementing information provided in the reference documents.

Other Systems and Issues – discussing additional lighting and non-lighting elements impacting the roadway 

user.

17. Key Words: 18. Distribution Statement:

Roadway lighting, street lighting, visibility, warrants, 

safety, adaptive lighting, lighting policy

No restrictions. This document is available to 

the public through National Technical 

Information Center, Springfield, Virginia 22161.

19. Security Classification (of this 

report):

20. Security Classification (of this 

page):

21. No of Pages: 22. Price:

Unclassified. Unclassified. 96

Form DOT F 1700.7 (06/98).
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Table of Contents

Policy and Guidance ....................................................................................................................... 1

1 Purpose of Lighting............................................................................................................... 2

1.1 Purpose of Handbook..................................................................................................... 2

1.2 Purpose of Roadway and Street Lighting....................................................................... 4

2 Federal Guidance and Recommendations Regarding Roadway Lighting ............................ 7

2.1 Determination of Lighting Need .................................................................................... 7

2.2 Determination of System Maintenance .......................................................................... 8

2.3 Design for Older Drivers................................................................................................ 8

2.4 Railroad Grade Crossings............................................................................................... 9

2.5 Crosswalks ................................................................................................................... 10

2.6 Roundabouts................................................................................................................. 11

Basic Terms and Concepts Related to Roadway Lighting ........................................................... 12

3 Vision and Fundamental Concepts...................................................................................... 13

3.1 Light and Vision........................................................................................................... 13

3.2 Fundamentals of Visibility........................................................................................... 15

3.3 Lighting Metrics........................................................................................................... 27

Warranting Criteria ....................................................................................................................... 30

4 Analysis for Lighting Needs ............................................................................................... 31

4.1 Warrants....................................................................................................................... 31

4.2 AASHTO Warranting System...................................................................................... 31

4.3 Warranting Method Example for Collector/Major/Local Streets ................................ 31

4.4 Warranting Method for Intersections........................................................................... 35

4.5 Other Examples of Intersection Warranting................................................................. 36

Lighting Impacts: General Considerations ................................................................................. 37

5 Considerations Concerning Lighting Systems.................................................................... 38

5.1 Environmental Impacts ................................................................................................ 38

5.2 Lighting Impacts on the Aging Population .................................................................. 44

6 Lighting System Selection .................................................................................................. 48

6.1 Design Considerations.................................................................................................. 48

6.2 Lighting Selection ........................................................................................................ 49

6.3 Luminaire Classification .............................................................................................. 51

6.4 Lighting Master Plans .................................................................................................. 55

Lighting Application Considerations............................................................................................ 57

7 Lighting Application ........................................................................................................... 58

7.1 System Layout and Geometry...................................................................................... 58

7.2 Scale and Inter-Relational Design................................................................................ 61
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7.3 Adaptive Lighting ........................................................................................................ 62

7.4 Performance Based System Design Relating to Environmental Impacts (e.g. Outdoor 

Site-Lighting Performance - OSP)........................................................................................... 65

7.5 Roadside Hazards......................................................................................................... 67

Other Systems and Issues Related to Roadway Lighting ............................................................. 70

8 Related Roadway Systems.................................................................................................. 71

8.1 Roadway Marking and Guidance................................................................................. 71

8.2 Impact of Vehicle Headlamps...................................................................................... 72

8.3 Temporary Roadway and Work Zone Lighting ........................................................... 73

8.4 Impact of Architectural/Aesthetic Lighting System for Roadway Facilities............... 75

9 Summary ............................................................................................................................. 79

References..................................................................................................................................... 80

Glossary of Terms......................................................................................................................... 83
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List of Figures

Figure 1a - Fatal Crash Rates per VMT for Day and Night (2009 FARS and NHTS data)........... 4

Figure 2 - Example of Data from the Crash Modification Factors Clearinghouse......................... 8

Figure 3 - Fundamental Structure of the Human Eye ................................................................... 13

Figure 4 - Electromagnetic Spectrum and Visible Spectrum........................................................ 14

Figure 5 - Eye Sensitivity Curves................................................................................................. 15

Figure 6 - Luminance Contrast (negative contrast above and positive below)............................. 16

Figure 7 - Effect of Color Contrast............................................................................................... 17

Figure 8 - Examples of AASHTO Calculated Safe Stopping Sight Distance with Variation Due 

to Grade .................................................................................................................................. 20

Figure 9 - Modifiers from MOVE Model..................................................................................... 21

Figure 10 - Figure from Rea's "A proposed system of photometry" - Lighting Res. Tech. 36.2 

(2004 pp. 85-111)................................................................................................................... 22

Figure 11 - Summary of Various Studies of Vision at Mesopic Light Levels ............................. 23

Figure 13 - Values of Unified Luminance for Various S/P ratios................................................ 26

Figure 14 - Inverse Square Law Calculation at a Point ................................................................ 27

Figure 15 - Calculation of Vertical Illuminance ........................................................................... 28

Figure 16 - Pavement Reflective Differences............................................................................... 28

Figure 18 – Spill Lighting, Glare and Skyglow............................................................................ 38

Figure 19 – Example of Skyglow ................................................................................................. 39

Figure 20 – Example of High Glare Street Lighting..................................................................... 39

Figure 21 – Spill Light Levels...................................................................................................... 40

Figure 22 – Example of Glare....................................................................................................... 42

Figure 23 – Source Intensity Levels ............................................................................................. 43

Figure 24 - Reduction in Visibility Level with Age ..................................................................... 45

Figure 25 - Effect of Aging on the Human Eye............................................................................ 46

Figure 26 - Impact of Glare and Light Level on the Visibility of Aging Drivers......................... 47

Figure 27 - Lamp Lumen Zones and Front Light Zone (from IESNA TM-15) ........................... 52

Figure 28 – LCS Comparison (IES TM-15-07)............................................................................ 53

Figure 29 – Bug Zones (IES TM-15-07) ...................................................................................... 54

Figure 30 – BUG Backlight (IES TM-15-07)............................................................................... 54

Figure 31 – Typical Pole Spacing................................................................................................. 58

Figure 32 – Pole Spacing .............................................................................................................. 59

Figure 33 - Highmast Pole Spacing .............................................................................................. 60

Figure 34 - Typical Lighting (Post-top and Highmast) ................................................................ 62

Figure 35 - Example Calculation of Lighting on Surfaces of Theoretical Box............................ 66

Figure 41 – Post-Mounted Delineators (PMDs)........................................................................... 72

Figure 42 – Headlamp Modeling Example................................................................................... 72

Figure 43 - Work Zone Lighting................................................................................................... 74

Figure 45 - Streetscape Lighting................................................................................................... 75

Figure 46 - Pedestrian Scale Lighting........................................................................................... 76

Figure 47 - Streetscape Lighting Layouts..................................................................................... 77

Figure 48 - Trees Blocking Light.................................................................................................. 78

Figure 49 - Comparison of sidewalk areas in winter (without leaves) and summer (with leaves)78

Figure 2 - Relationship between candelas, lumens, lux, and footcandles: ................................... 86
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Policy and Guidance

This section discusses the references, policy, and recommendations used by the 

Federal Highway Administration in evaluating and administering funds for 

roadway and street lighting projects.
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1 Purpose of Lighting 

1.1 Purpose of Handbook

This handbook has been prepared to provide guidance to 

lighting designers and State, city, and town officials 

concerning the design and application of roadway lighting. 

It is not intended to be a detailed design guide. It is 

primarily a resource for policy makers and the design and 

construction community to evaluate potential need, 

benefits, and applicable references when considering a 

roadway or street lighting system. Documents available 

from organizations such as the American Association of 

State Highway and Transportation Officials (AASHTO), 

the Illuminating Engineering Society (IES), and the Commission Internationale de l’Eclairage 

(CIE) offer recommendations on lighting levels, lighting configurations, and other 

considerations. This handbook directs users to that information where applicable, and provide 

supplemental information on topics not addressed in those documents.

The document is divided into six areas of discussion. These areas include:

Policy and Guidance – discussing references, policy, and recommendations used by FHWA in 

evaluating and administering funds for roadway and street lighting projects.

Basic Terms and Concepts – discussing descriptions of significant terms and concepts used in 

roadway and street lighting projects.

Warranting Criteria – including various warranting methods available when considering 

lighting.

Lighting Impacts – discussing various impacts (both positive and negative) of lighting systems 

and ways to control and mitigate.

Application Considerations – supplementing information provided in the reference documents.

Other Systems and Issues – discussing additional lighting and non-lighting elements impacting 

the roadway user.

This handbook is an update to the 1978 FHWA Lighting Handbook 78-15 as well as the 1983 

addendum to chapter 6 of the handbook.

Key documents that provide guidance and criteria for roadway lighting and associated 

applications are listed below. The latest versions of these documents should be used as 

references for design projects.

AASHTO GL-6 Roadway Lighting Design Guide (www.transportation.org)

ANSI/IES RP-8 Standard Practice for Roadway Lighting (www.ies.org)

This handbook 

supplements the 

guidance provided 

by AASHTO and 

IES
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ANSI/IES RP-22 Standard Practice for Tunnel Lighting (www.ies.org)

ANSI/IES RP-22 Standard Practice for Tunnel Lighting (www.ies.org)

IES DG-19 Design Guide for Roundabout Lighting (www.ies.org)

FHWA-RD-01-103 Highway Design Handbook for Older Drivers and Pedestrians 

(www.fhwa.dot.gov )

FHWA-SA-07-010 Railroad-Highway Grade Crossing Handbook (www.fhwa.dot.gov)

FHWA-HRT-08-053 Informational Report on Lighting Design for Midblock Crosswalks 

(www.fhwa.dot.gov)

TAC Guide for the Design of Roadway Lighting 2006 Edition (www.tac-atc.ca)

NCHRP 672 Roundabouts: An Informational Guide – Second Edition (www.trb.org)

Additional useful documents include:

AASHTO RSDG-3 Roadside Design Guide 4th Edition 2011 (www.transportation.org)

AASHTO Highway Safety Manual (www.highwaysafetymanual.org)

AASHTO A Policy on Geometric Design of Highways and Streets 6th Edition 2011

(www.transportation.org)
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Fatal Crash Rate per Vehicle Miles Traveled

1.2 Purpose of Roadway and Street Lighting

Driving or walking on, or across, a roadway is less safe in 

darkness than in a lighted area, due to the reduced 

visibility of hazards and pedestrians. Though the number 

of fatal crashes occurring in daylight is about the same as 

those that occur in darkness, only 25 percent of vehiclemiles traveled occur at night. Because of that the 

nighttime fatality rate is three times the daytime rate, as 

illustrated in Figure 1a. Figure 1b shows the difference in 

the number of fatal crashes on lit and unlit roadways.

Figure 1a - Fatal Crash Rates per VMT for Day and Night (2009 FARS and NHTS data)

Studies have shown 

a reduction in 

nighttime fatal 

crashes of up to 

60% with the use of 

roadway lighting (5)
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Figure 1b - Fatal Crashes during Darkness by Lighting Condition (2009 FARS data)

On a fundamental level, driving is largely a visual task. Being able to adequately see the 

road/street ahead and observe conflicting traffic and the behavior of other highway users is 

integral to the driving task. Lighting significantly improves the visibility of the roadway, 

increases sight distance, and makes roadside obstacles more noticeable to the driver, and 

therefore more avoidable.

Roadway lighting is a proven safety countermeasure. The positive safety effects of lighting have 

been documented in various reports and publications. For example, an FHWA/AASHTO 

international scan documented (1) that many countries showed a 20 to 30 percent reduction in 

the number of crashes when lighting was installed. More recently, the FHWA Signalized 

Intersection Informational Guide (3) reported that adding lighting can reduce nighttime crashes 

by 50 percent and reduce fatal crashes by 43 percent. There have been many other studies that 

document similar safety benefits of lighting.

In addition to traffic safety, adequate lighting provides clear benefits in terms of personal 

security. Roadway lighting often serves the purpose of safeguarding personal safety for

pedestrians, bicyclists, and transit users as they travel along and across roadways. Deep shadows 

or darkness reduce personal security, and walking, bicycling or commercial activities may 

become uncomfortable or unsafe. Thus, ensuring that the lighting provides minimum acceptable 

levels of illumination is of great importance to all users of a roadway environment.
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Noteworthy research included as part of the FHWA CMF Clearinghouse discussing the effects of 

road lighting on safety and driver performance includes:

• Elvik and Vaa (2004)(4) reviewed 38 studies comparing the impact of lighting on previously 

unlit roads and found a 64 percent reduction of fatal crashes, 28 percent reduction in injury 

crashes, and 17 percent reduction in property-damage-only crashes after the roadways were 

lit.

• Per Ole Wanvik (2009)(5) used various study methods and literature review to determine the 

usefulness of road lighting as a countermeasure, and found that the mean effect of roadway 

lighting is a 28 percent reduction in injury crashes, a 60 percent reduction in fatal crashes, a 

45percent reduction in injury crashes involving pedestrians, a 35 percent reduction in injury 

crashes at rural intersections, and a 50 percent reduction in injury crashes on freeways.

Other research of note include:

• Lipinski and Wortman (1976)(6) showed a 45 percent reduction in the night crash rate at 

rural at-grade intersections.

• Walker and Roberts (1976)(7) found a 52 percent reduction in nighttime crashes at 47 

intersections in a 6-year before-and-after study.

• The Minnesota Local Road Research Board (2006)(8), comparing rural intersection locations 

before and after lighting had been installed, indicated that 44 percent of the intersections 

showed a reduction in the number of nighttime crashes after lighting was installed.
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2 Federal Guidance and Recommendations Regarding 

Roadway Lighting

2.1 Determination of Lighting Need

The FHWA administers funding for State roadway lighting projects that meet certain 

requirements in terms of need. These projects are eligible under Section 148 of Title 23, United 

States Code (Highway Safety Improvement Program). In addition, these projects are eligible for 

the increased Federal share under 23 U.S.C. 120(c).

When Federal aid is used for a lighting project, the applicant can support the need for a roadway 

lighting system by including the following items:

• A warrant analysis showing that lighting is a 

warranted safety feature.

• A project criteria document showing that the 

design criteria established by AASHTO or the IES 

will be used and met as part of the design.

A safety analysis and study showing that a lighting 

system is a cost-effective safety alternative for the project 

may also be considered. There are various ways of 

executing a study of this type. One is to use the 

AASHTO Highway Safety Manual – 2010 (HSM)(25). 

The HSM has assembled currently available information 

on crash frequency and severity so that various 

improvements to roadways could be quantified and 

evaluated in terms of their effectiveness. Some of the effects of various treatments, such as 

geometric improvements or operational changes on roadways, are quantified as Crash 

Modification Factors (CMFs). CMFs represent the change expected in crash frequency due to a 

specific change in conditions.

For example, in looking at the impact of highway lighting on all roadway types that previously 

had no lighting, for nighttime injury crashes, the HSM reports that research has shown a resultant 

CMF of 0.72 (showing that there would be a reduction of 28 percent in nighttime injury crash 

The FHWA review 

process requires a 

warrant analysis, 

project criteria 

document, maintenance 

plan, and MOU
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types). So if the expected average crash frequency is 10 injury crashes/year for a no-lighting 

condition, then after implementation of a highway lighting system one would expect 10 X 0.72 

CMF = 7.2 injury crashes/year.

The amount of information for crash analysis and evaluation is actively growing and can be 

found at the Crash Modification Factors Clearinghouse at www.cmfclearinghouse.org. In this 

clearinghouse the viewer can sort through data by the type of countermeasure, crash type, crash 

severity, and roadway type. The viewer can also see a measure of accuracy and precision of the 

data, as well as applicability, as judged by a panel of reviewers, and rated with a system using a 

1-5 star scale.

Figure 2 - Example of Data from the Crash Modification Factors Clearinghouse

2.2 Determination of System Maintenance

FHWA requires that federally funded lighting systems be adequately maintained. The Federal 

Regulations (23 CFR 1.27) state “The responsibility imposed upon the State highway 

department, pursuant to 23 U.S.C. 116, for the maintenance of projects shall be carried out in 

accordance with policies and procedures issued by the Administrator. The State highway 

department may provide for such maintenance by formal agreement with any adequately 

equipped county, municipality or other governmental instrumentality, but such an agreement 

shall not relieve the State highway department of its responsibility for such maintenance.”

2.3 Design for Older Drivers

The FHWA has prepared a Highway Design Handbook for Older Drivers and Pedestrians (9)

that “provides practitioners with a practical information source that links older road user 

characteristics to highway design, operational, and traffic engineering recommendations by 
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addressing specific roadway features.” The handbook “supplements existing standards and 

guidelines in the areas of highway geometry, operations, and traffic control devices.”

Included in the handbook are recommendations for fixed lighting installations at intersections 

and interchanges for the older driver. This handbook is not intended to constitute a new standard 

of required practice, but to provide a resource to practitioners and owners during the decisionmaking process.

The recommendations for intersections include the following:

Wherever feasible, fixed lighting installations are recommended as follows:

1. Where the potential for wrong-way movements is indicated through crash experience 

or engineering judgment.

2. Where twilight or nighttime pedestrian volumes are high.

3. Where shifting lane alignment, turn-only lane assignment, or a pavement-width 

transition forces a path-following adjustment at or near the intersection

The handbook also recommends regular cleaning of lamp lenses, and lamp replacement when 

output has degraded by 20 percent or more of peak performance (based on hours of service and 

manufacturer’s specifications), for all fixed lighting installations at intersections.

The recommendations for interchanges state:

Complete interchange lighting (CIL) is the preferred practice, but where a CIL system in 

not feasible to implement, a partial interchange lighting (PIL) system comprised of two 

high-mast installations (e.g. 18- to 46-m- [60- to 150-ft-] high structures with 2 to 12 

luminaires per structure) per ramp is recommended, with one fixture located on the inner 

ramp curve near the gore, and one fixture located on the outer curve of the ramp, midway 

through the controlling curvature.

2.4 Railroad Grade Crossings

The FHWA has a handbook (10) dealing with railroad-highway crossings that is meant to

“provide a single reference document on prevalent and best practices as well as adopted 

standards relative to highway-rail grade crossings.” The abstract states: “The handbook provides 

general information on highway-rail crossings; characteristics of the crossing environment and 

users; and the physical and operational improvements that can be made at highway-rail grade 

crossings to enhance the safety and operation of both highway and rail traffic over crossing 

intersections. The guidelines and alternative improvements presented in this handbook are 

primarily those that have proved effective and are accepted nationwide.”

The recommendations for lighting state:

“Illumination at a crossing may be effective in reducing nighttime crashes. Illuminating most 

crossings is technically feasible because more than 90 percent of all crossings have 

commercial power available. Illumination may be effective under the following conditions:

• Nighttime train operations.
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• Low train speeds.

• Blockage of crossings for long periods at night.

• Crash history indicating that motorists often fail to detect trains or traffic control devices 

at night.

• Horizontal and/or vertical alignment of highway approach such that vehicle headlight 

beam does not fall on the train until the vehicle has passed the safe stopping distance.

• Long dark trains, such as unit coal trains.

• Restricted sight or stopping distance in rural areas.

• Humped crossings where oncoming vehicle headlights are visible under trains.

• Low ambient light levels.

• A highly reliable source of power.

Luminaires may provide a low-cost alternative to active traffic control devices on industrial 

or mine tracks where switching operations are carried out at night.

Luminaire supports should be placed in accordance with the principles in the Manual for

Assessing Safety Hardware (MASH) and NCHRP Report 350.117. If they are placed in the 

clear zone on a high-speed road, they should be designed with a breakaway base.”

2.5 Crosswalks

FHWA has prepared an informational report on crosswalk lighting (FHWA-HRT-08-053:

Informational Report on Lighting Design for Midblock Crosswalks)(11). The report “provides 

information on lighting parameters and design criteria that should be considered when installing 

fixed roadway lighting for midblock crosswalks. The information is based on static and dynamic 

experiments of driver performance with regard to the detection of pedestrians and surrogates in 

midblock crosswalks. Experimental condition variables included lamp type (high-pressure 

sodium and metal halide), vertical illuminance level, color of pedestrian clothing, position of the 

pedestrians and surrogates in the crosswalk, and the presence of glare. Two additional lighting 

systems, a Probeam luminaire and ground-installed LEDs, were also evaluated. The research 

found that a vertical illuminance of 20 lx in the crosswalk, measured at a height of 1.5 m (5 ft) 

from the road surface, provided adequate detection distances in most circumstances. Although 

the research was constrained to midblock placements of crosswalks, the report includes a brief 

discussion of considerations in lighting crosswalks co-located with intersections.”

The results of this report were included in the revised IES RP-8 Standard Practice for Roadway 

Lighting (29)
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2.6 Roundabouts

FHWA has prepared and informational guide on the design of roundabouts (NCHRP Report No. 

672 : Roundabouts: An Informational Guide – Second Edition)(31). In this document it states 

that illumination is recommended for all roundabouts, including those in rural environments, and 

gives other advice for mitigation if lighting cannot be provided. The document also includes 

typical lighting levels for approach roadways which are then summed to determine the 

roundabout lighting levels.
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Basic Terms and Concepts Related to Roadway Lighting

This section includes descriptions of key terms and concepts used in FHWA, AASHTO, and IES 

documents with regard to lighting, as well as some emerging concepts. Because they are 

already quantified in AASHTO and IES documents, or are still under study, these concepts are 

not quantified here. However, they merit close scrutiny in a discussion of roadway lighting.
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3 Vision and Fundamental Concepts

3.1 Light and Vision

Many factors influence our ability to see an object while driving. These include the contrast of 

the object, both photometric and color (i.e., the difference between the object and its 

background); the driver’s adaptation level (impacted by the brightness of the road and surrounds, 

how much glare is present from approaching vehicles and luminaires, etc.), and how long the

driver has to view a hazard. Understanding these factors is vitally important to developing an 

effective design for roadway and street lighting.

3.1.1 Structure of the Eye

Figure 3 - Fundamental Structure of the Human Eye

The retina contains two types of photoreceptors, rods and cones. Rods, which are most 

numerous in the retina, are more sensitive and function at a lower light level than the cones. 

Rods are also not sensitive to color. Cones are sensitive to color and are divided into red (64

percent), green (32 percent), and blue (2 percent) cones. They are concentrated in the macula of 

the eye with most being in the center of that region, the fovea, which contains only cones.

In the 1990s a third type of photoreceptor was discovered and named “intrinsically 

photosensitive Retinal Ganglion Cells” (ipRGCs). More research is being conducted into the 

function of these photoreceptors as they relate to controlling adaptation, restriction of the pupil, 

and circadian rhythms. Their application to roadway lighting at this time is unclear.
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Adaptation of the eye occurs in the retina, as the eye adjusts to the varying brightness of a scene 

caused by the overhead lighting system, approaching vehicle headlights, and ambient lighting 

conditions. States of adaptation include:

• Scotopic Vision – Vision by the normal human eye, when only the rods of the retina are 

being used, where the adaptation luminance at the eye is 0.001 cd/m2 or lower. At this state 

of adaptation there is no sensation of color.

• Mesopic Vision – when both the rods and cones are active, at varying percentages based on 

based on conditions, where the adaptation luminance at the eye is between 0.001 cd/m2 and 

3.0 cd/m2. At this state of adaptation the eye is sensitive to color (more “blue” at the lower 

end of the adaptation range and more “red” at the higher).

• Photopic Vision – when predominantly cones are active and normal color vision is possible, 

where the adaptation luminance at the eye is 3.0 cd/m2 and above.

3.1.2 Spectral Properties

Visible light is a limited range of electromagnetic radiation. Within this range, different 

wavelengths are seen as different colors. As Figure 4 demonstrates, radiation with a shorter 

wavelength on the visible spectrum is perceived as more “blue” in color, while radiation with a 

longer wavelength is perceived as more “red.”

Figure 4 - Electromagnetic Spectrum and Visible Spectrum

The eye has varying sensitivity to different wavelengths within the visible spectrum depending 

on the state of adaptation.
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Figure 5 - Eye Sensitivity Curves

The solid curve in Figure 5 is referred to as the V Lambda V(l) curve. This curve represents the 

spectral efficiency of a source when the eye is using photopic vision. Sources with wavelengths 

in the more “yellow” range, such as high pressure sodium, would be rated at a higher power 

value (lumen) than a source with the same amount of more “blue” content, such as metal halide 

of higher Correlated Color Temperature (CCT) LED sources.

The dashed curve represents the eye response when using scotopic vision. This shows that at 

very low light levels sources with more “blue” content would be allocated a higher lumen value.

3.2 Fundamentals of Visibility

3.2.1 Contrast

Objects are seen by “contrast,” which is basically the visible difference between an object and its 

background. From a luminance perspective, an object that is darker than its background will be 

seen by “negative” contrast, and an object that is sufficiently brighter than its background will be 

seen by “positive” contrast. In Figure 6, the upright object shown in the upper frames is in 

negative contrast (a darker object silhouetted against a brighter background), and in the lower 

frames it is in positive contrast (brighter object against darker background). It is also worth 

noting that contrast may vary within the object itself. The upper right frame shows the bottom 

portion of the object in negative contrast, and the upper portion in positive contrast. The value of 

contrast also changes along its length.

The formula for calculating contrast (Weber contrast) is:
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Contrast = LObject − LBackground

LBackground

LObject = Luminance of the object 

LBackground = Luminance of the background

If we use the luminance values shown in the upper portion of the figure we can calculate that the 

lower portion of the cylinder, where the roadway is the background, has a contrast of (1-22)/22 =

-0.95, with the negative value denoting that it is negative contrast.

Figure 6 - Luminance Contrast (negative contrast above and positive below)

This contrast value is the luminance contrast of the object. How much contrast you need to see 

an object depends on a number of things, including the size of the object, how long you look at 

it, your age, and your adaptation luminance (determined by the luminance of the road, glare from 

lights, approaching headlights, and ambient lighting levels). This is called the threshold contrast 

and is based on the probability of detection of an object 50 percent of the time (Adrian, 1989)

(12). The purpose of a roadway lighting system is to produce actual contrast of an object on the 

road greater than the threshold contrast required by the driver for detecting it. Studies
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(Blackwell) (13) suggest that good visibility of objects can be achieved if the actual contrast is 3 

to 4 times the required threshold contrast. Obtaining this contrast is primarily a function of the 

lighting placement and optical characteristics.

Applying contrast metrics to roadway lighting, however, is situational and depends on many 

variables. Designers should nevertheless be aware of the key elements under their control:

• Control/reduce the glare generated by the roadway lighting system.

• If possible, reduction of glare from approaching headlights by median widths and treatments 

will increase visibility.

Color also provides additive contrast benefits. As shown in Figure 7, the visibility of objects and 

pedestrians can be improved by color contrast. This is dependent upon the color of the object or 

clothing as well as the color rendering ability of the source used for roadway lighting. In looking 

at the pedestrian’s red shirt or the approaching red vehicle in the left frame of Figure 7, we can 

tell that color contrast provides additional visibility. This effect is quite variable, however, so it 

is not quantified for roadway lighting.

Figure 7 - Effect of Color Contrast

3.2.2 Glare

Non-uniformities in the visual field, particularly those caused by bright sources, affect the

adaptation level of the eye. Because these sources tend to fluctuate as the driver proceeds, the

adaptation level is constantly changing (“transient adaptation”). Roadway lighting thus aids the 

eye in adapting to an increased level of luminance than can be provided by headlights alone. 

Bright sources create other effects, collectively termed “glare,” which should be avoided as

much as is practical.

Disability Glare
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Light rays passing through the eye are slightly scattered, primarily because of diffusion in the

lens and the vitreous humor that fills the anterior chamber of the eye. When a light source of

high intensity is present in the field of view, this scattering tends to superimpose a luminous haze 

over the retina. The effect is similar to looking at the scene through a luminous veil. The

luminance of this “veil” is added to both the task and background luminance, thus having the 

effect of reducing contrast. The effect is termed “disability glare” or “veiling luminance,” and it

may be numerically evaluated by expressing the luminance of the equivalent luminous veil. A

well-known example of this is trying to see beyond oncoming headlights at night. Because of 

contrast reduction by disability glare, visibility is decreased. Increasing luminance will 

counteract this effect by reducing the eye’s contrast sensitivity. A well designed roadway 

lighting system will minimize glare by employing luminaires that have proper optical design 

(e.g., cutoff or full-cutoff). Disability glare should be limited to the recommended veiling 

luminance ratios included in the AASHTO (26) and IES(28) recommendations.

Discomfort Glare

Discomfort glare is a further result of overly bright light sources in the field of view, and causes 

a sense of pain or annoyance. While its exact cause is not known, it may result from pain in the 

muscles that cause closing of the pupil. Disability glare and discomfort glare normally 

accompany one another, and beneficial luminaire light control that reduces one form of glare is 

likely to reduce the other. Discomfort glare, which can cause effects from an increased blink rate 

to tears and pain, does not reduce visibility. It is also generally accepted that reducing disability 

glare will reduce discomfort glare. It is possible, however, to reduce discomfort glare and 

increase disability glare. North American roadway lighting standards do not specify numerical 

limits for discomfort glare. Methods exist to quantify 

discomfort glare for roadway lighting, but are mostly

subjective. Also, no instrument has been developed for 

the measurement of discomfort glare. The 

Commission Internationale de l’Eclairage 

(International Commission on Illumination - CIE) uses

a “Glaremark System,” which is a graphical method 

using a scale of 1 to 10 to rate lighting systems. 

However, there is no current practical use or 

application of this method.

Nuisance Glare

The presence of extraneous light in the field of view 

may cause a nuisance or distraction to the driver, 

independent of the effects of disability and discomfort. 

Bright light sources tend to cause distraction, and the eye may be drawn to them. Lighting that is 

used for advertising, for example, may cause visual clutter and add complexity to the scene, 

making the driving task more challenging. There is no defined method or measurement system 

for assessing nuisance glare.

Disability glare is one 

of the most important 

elements to control in 

a lighting system. It 

affects your ability to 

adequately see, 

particularly for older 

drivers.
LIGHTING HANDBOOK

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3.2.3 Perception-Reaction Time

Many components make up perception-reaction time. A motorist, in order to stop or avoid a 

hazard or person on a roadway, must first detect the object’s presence, recognize or otherwise 

assess the object, then react to that determination. The mechanical operation of braking/steering 

mechanisms, as well as road/tire/vehicle performance conditions, also factor into perceptionreaction time.

From a reaction time perspective, key elements include whether a situation is expected, cognitive 

load and distractions, personal physical response attributes, age, and other factors, Green (22) 

classified reaction times, adding an additional condition of “surprise”, in the following way:

• Expected - The driver is alert and aware of the good possibility that braking will be 

necessary. This is the absolute best reaction time possible. The best estimate is 0.7 

seconds (AASHTO Green Book (14) states it as approx. 0.6 seconds). Of this, 0.5 is 

perception and 0.2 is movement, the time required to release the accelerator and to 

depress the brake pedal. 

• Unexpected - The driver detects a common road signal such as a brake from the car ahead 

or from a traffic signal. Reaction time is somewhat slower, about 1.25 seconds

(AASHTO Green Book (14) states it is approx. 35% longer than the expected condition). 

This is due to the increase in perception time to over a second with movement time still 

about 0.2 second. 

• Surprise - The driver encounters a very unusual circumstance, such as a pedestrian or 

another car crossing the road in the near distance. T here is extra time needed to interpret 

the event and to decide upon response. Reaction time depends to some extent on the 

distance to the obstacle and whether it is approaching from the side and is first seen in 

peripheral vision. The best estimate is 1.5 seconds for side incursions and perhaps a few 

tenths of a second faster for straight-ahead obstacles. Perception time is 1.2 seconds 

while movement time lengthens to 0.3 second.”

For example a person traveling at 55mph is moving at approximately 80 ft/sec. The distance 

traveled during reaction time alone can be anywhere from 40’ to 120’. When this is added to the 

distance covered during actual stopping, the total can be quite significant.

The AASHTO Policy on Geometric Design of Streets and Highways (14) include a method for 

determining stopping distance based on a number of factors including reaction time. Figure 8

shows examples of estimated Safe Stopping Sight Distance (SSSD) based on that AASHTO 

method with modifiers showing the impact of grades.
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Figure 8 - Examples of AASHTO Calculated Safe Stopping Sight Distance with Variation Due to Grade

Although stopping distances are not applied to roadway 

lighting, with the exception of tunnel lighting systems, the 

distances shown demonstrate one of the benefits of roadway 

lighting. If we assume most low beam vehicle headlights 

have an effectiveness of approximately 300’ in front of the 

vehicle (Green, 2008) (23), speeds of 40 mph and above 

have stopping distances greater than that distance. In order 

for a driver to detect a pedestrian or road hazard in time to 

stop at higher speeds, the roadway lighting system needs to 

provide that necessary visibility.

3.2.4 Spectral Effect Models

As discussed in the Light and Vision section of this handbook, the color of light (wavelength) 

produces different responses in the eye depending on its state of adaptation. There were 

established response curves for adaptation in the photopic and scotopic states, but none 

established for the mesopic state which would change depending on the adaptation luminance. 

However, models have been developed in recent years suggesting modifying factors which can 

be applied to adjust the calculated photopic luminance value to the expected mesopic luminance 

based on the source spectral distribution (Scotopic/Photopic –S/P- ratio). Ongoing discussion 

and further research is being performed in this area so these models are provided as information.

At speeds above 

40mph roadway 

lighting provides 

visibility of objects 

beyond the effective 

range of headlights
LIGHTING HANDBOOK

21

MOVE – Mesopic Optimisation of Visual Efficiency

The MOVE method was developed from tests conducted at the TNO (Netherlands), University 

of Veszprem (Hungary), Darmstadt University of Technology (Germany), City University (UK), 

and Helsinki University of Technology (Finland). From this research modifiers were developed 

for adaptation luminance and source S/P ratios of various values. Those modifiers are shown in 

Figure 9.

As an example, a high pressure sodium roadway fixture might have an S/P ratio of around 0.6; if 

lamped with pulse start metal halide it might be around 1.4; and with an LED roadway fixture it 

may be 2.0. So using the MOVE multipliers, if we assume the adaptation luminance is 1 cd/m2

the mesopic luminance for the HPS luminaire would be approximately 0.93 cd/m2, the MH 

luminaire would be approximately 1.06 cd/m2, and the LED luminaire would be approximately 

1.15 cd/m2

.

Figure 9 - Modifiers from MOVE Model
LIGHTING HANDBOOK

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Rea et al - Unified System of Photometry

The unified system of photometry was developed by conducting a field study on a test road 

where subjects were asked to identify the orientation of various size Landolt rings displayed on 

small targets in the center of the roadway. Their reaction time was measured, as well as their

subjective impressions of visibility. These results were then compared with various models for 

photometry in the mesopic region. The comparative models used are shown in Figure 10. 

Figure 10 - Figure from Rea's "A proposed system of photometry" - Lighting Res. Tech. 36.2 (2004 pp. 85-111)
LIGHTING HANDBOOK

23

Rea’s research also included a condensed summary of other research and models (shown in 

Figure 11) to allow for easy comparison’

Figure 11 - Summary of Various Studies of Vision at Mesopic Light Levels
LIGHTING HANDBOOK

24

(Rea et al, "A proposed unified system of photometry”) (15)

The results of the model recommended by Rea (15) show an impact of using higher S/P ratio 

sources of moderate impact for most recommended roadway lighting levels with no difference in 

the visual efficacy multiplier for levels freeway lighting levels of around 0.6 cd/m2 and more 

significant difference of over 20% for the lowest recommended lighting level streets like low 

pedestrian volume residential designed to 0.3 cd/m2.

Figure 12 shows some S/P ratios from various light sources as reference. Figure 13 shows the 

different unified values which would result from applying Rea’s unified method of photometry.

Figure 12 – Table showing S/P Ratios of Commercially Available Light Sources

(LRC ASSIST - Outdoor Lighting: Visual Efficacy, Volume 6, Issue 2, January 2009)

For example, if the photopic luminance level is 0.3 cd/m2 is then under a source with an S/P ratio

like low pressure sodium (S/P of 0.25) the equivalent mesopic luminance level would be 0.2012

cd/m2. If instead the source was a metal halide lamp with an S/P ratio of 1.55, then the mesopic 

luminance level would be 0.3402 cd/m2 .
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LIGHTING HANDBOOK

26

Figure 13 - Values of Unified Luminance for Various S/P ratios

In 2010 the Commission Internationale de l’Eclairage 

(CIE) issued the publication CIE 191: Recommended 

System for Mesopic Photometry Based on Visual 

Performance, which is essentially a compromise of the 

Rea and the MOVE methods.

At this time, FHWA does not make any 

recommendations concerning spectral effects or their 

associated models. Research is still underway and the 

results of this research are being worked into 

recommendations made by AASHTO and IES.

Higher S/P ratio 

“white” light sources 

do have an effect on 

visibility. The proper 

application of this 

effect is still under 

study.
LIGHTING HANDBOOK

27

3.3 Lighting Metrics

Illuminance

Illuminance is the amount of light that falls onto a surface. Illuminance is measured as the 

amount of lumens per unit area either in footcandles (lumens/ft2

) or in lux (lumens/m2). 

Illuminance is variable by the square of the distance from the source. As a lighting metric, 

illuminance is simple to calculate and measure, not needing to take into account the reflection 

properties of the roadway surface and only requiring a fairly inexpensive illuminance meter for 

field verification. The drawback to this metric is that the amount of luminous flux reaching a 

surface is often not indicative of how bright a surface will be or how well a person can see.

Figure 14 - Inverse Square Law Calculation at a Point

Vertical Illuminance

Vertical illuminance is the amount of illuminance that lands on a vertical surface. The units and 

properties are the same as horizontal illuminance. As it relates to roadway lighting, vertical 

illuminance is a reasonable criterion for determining the amount of light landing on pedestrians. 

It is also used as a criterion in determining adequate illumination for facial recognition. For 

roadway applications, vertical illuminance is most often used at a 1.5 meter height above the 

roadway or sidewalk. The 1.5 meter height is a commonly used metric in outdoor criteria as the

height of a pedestrian’s face.
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Figure 15 - Calculation of Vertical Illuminance

Luminance

Luminance is the amount of light that reflects from a surface in the direction of the observer. It 

is often referred to as the “brightness” of the surface, although apparent brightness has a number 

of other factors to take into consideration. It is, however, a more complete metric than 

illuminance because it considers not only the amount of light that reaches a surface, but also how 

much of that light is reflected towards the driver.

In Figure 16, the roadway has the same illuminance values across both lanes. The luminance 

values, however, are twice as high for the right lane, which is how the road appears to an 

observer

Figure 16 - Pavement Reflective Differences
LIGHTING HANDBOOK

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Veiling Luminance Ratio

The veiling luminance ratio is a metric used by the IES and AASHTO to determine the amount 

of glare generated by a lighting system. The ratio is the maximum veiling luminance at the 

driver’s eye divided by the average pavement luminance of the roadway. Because glare is a 

function of adaptation luminance, the road is used as the assumed scene from which the 

luminance reaches the eye.

For example, if a roadway lighting system was designed to a lighting level of 0.6 cd/m2 using 

250watt high pressure sodium fixtures of a certain distribution type, the glare would be a certain 

calculated veiling luminance ratio with the maximum veiling luminance probably being 

generated from the closest luminaire and the average roadway luminance being 0.6 cd/m2

. If the 

system was changed to use 400 watt lamps, you could expect the veiling luminance to increase 

by the change in output. But since the scene brightness (roadway luminance) will also increase 

by the proportional change in output, the veiling luminance ratio or glare of the lighting system 

will not change.

There are also other metrics which are used to express glare. CIE uses Threshold Increment (TI) 

as its primary method. TI is based on threshold contrast, which is the amount of contrast 

between and object and its background when the probability of detection is 50 percent. When 

glare is introduced, the probability of an object being seen drops below 50 percent, therefore not 

reaching threshold contrast, which means the contrast needs to be increased. TI is the percentage

the contrast needs to be increased in order to achieve threshold contrast again.
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30

Warranting Criteria

This section includes example methods for determining lighting warrant for roadway lighting 

systems. AASHTO provides warranting methods for continuous freeway lighting, complete 

interchange lighting, and partial interchange lighting. Other methods for collector/arterial/local 

roads as well as for intersections have been included in this section for information.

It is important to note that warrants do not represent a requirement to provide lighting. 

Satisfaction of a lighting warrant shall not in itself require the installation of a lighting system. 
LIGHTING HANDBOOK

31

4 Analysis for Lighting Needs

4.1 Warrants

Lighting warrants assist in evaluating locations where lighting will maximize benefit based on 

defined conditions or rating systems. Meeting these warrants does not obligate the state or other 

agencies to provide lighting. Conversely, using engineering judgment in addition to warrants, 

considering things such as roadway geometry, high crash

rates, or frequent occurrences of poor weather conditions 

such as rain, fog, ice, or snow, may influence a decision on 

whether to install lighting. 

Warrants indicate where lighting may be beneficial, but 

should not be interpreted as an absolute indication of 

whether or not lighting is required. The need for lighting 

should be determined by sound engineering judgment and 

rests with the agency having jurisdiction over the roadway.

4.2 AASHTO Warranting System

Warrants for highways, freeways, interchanges and bridges

may be undertaken using the AASHTO Roadway Lighting 

Design Guide Warranting System. AASHTO defines

warrants for Continuous Freeway Lighting (CFL), Complete Interchange Lighting (CIL) and

Partial Interchange Lighting (PIL) based on warrant conditions including:

• Traffic volumes

• Spacing of freeway interchanges

• Lighting in adjacent areas

• Night-to-day crash ratio

AASHTO believes it is desirable to provide lighting on long bridges in urban and suburban areas 

even if the approaches are not lighted. On bridges without full shoulders, lighting can enhance

both safety and utility of the bridges, and is therefore recommended. Where bridges are 

provided with sidewalks for pedestrian movements, lighting is recommended for pedestrian 

safety and guidance.

4.3 Warranting Method Example for Collector/Major/Local Streets

The warrant system presented is based on the Transportation Association of Canada (TAC)

Guide for the Design of Roadway Lighting (27) which was based on the 1978 Roadway Lighting 

Handbook published by the U.S. Department of Transportation. 

Warrants do not 

represent a 

requirement to 

light, only an 

indication of 

situations where 

lighting should be 

investigated
LIGHTING HANDBOOK

32

The warrant system is based on factors grouped into geometric, operational, environmental, and 

crash factors. For each factor a numeric rating (R) from 1 to 5 corresponding to the defined 

criterion is defined. Each criterion is assigned a weight (W) to indicate its relative importance. 

The rating value (R) is multiplied by the weight (W) to obtain a point-score (R x W) for each 

criterion characteristic, indicating its relative significance. The overall point-score for all items 

indicates the need for lighting, as well as the relative risk on that road compared with other 

roadways. 

When undertaking a warrant analysis, the length of roadway segment being analyzed should be 

as long as possible, and should take into account future development. Where the roadway 

classification or roadway land use classification changes, a separate warrant analysis should be

considered for each roadway section. Where classifications are relatively constant along the 

segment of roadway under consideration, a single warrant analysis may be undertaken.

Classification factors listed on the warrant sheets are defined as follows:

4.3.1 Geometric Factors

Includes key geometric factors listed for the length of roadway to which the warrant is being 

applied. These include:

• Number of lanes

• Lane width

• Number of median openings per kilometer

• Driveways and entrances per kilometer

• Horizontal curve radius

• Vertical grade

• Sight distance

• Parking

The worst-case rating factors (R) shall apply for the entire length of road being considered. The 

weighted value is very high for sharp horizontal curve radii.

4.3.2 Operational Factors

Includes operational factors for the entire length of roadway to which the warrant is being 

applied. These include:

• Signalized intersections

• Left turn lanes

• Median width

• Operating or posted speed

• Pedestrian activity (conflict) levels (ref to IESNA RP-8 for definition of high, medium or low 

activity)

The worst-case rating factors (R) shall apply for the entire length of road being considered. The 

weighted value is high for pedestrian activity level.
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33

4.3.3 Environmental Factors

Includes environmental factors for the entire length of road to which the warrant is being applied. 

These include:

• Percentage of development adjacent to the roadway. Adjacent development must be a 

reasonable distance from the roadway and must tie into the roadway for which the warrant is 

being undertaken via a driveway or intersection which generates a reasonable amount of 

traffic. Determining the amount of ambient lighting present in an area depends on the 

judgment of the individual performing the warrant analysis. As a general guide, the 

following ambient lighting definitions may be applied:

− Sparse - Would typically include rural freeways and highways with little or no 

development outside of city boundaries.

− Moderate - Would typically include rural or urban roads with some building lighting 

and development outside of commercial areas. Areas with residential and industrial 

development will typically have moderate ambient lighting.

− Distracting - Would typically be downtown commercial areas with well-lighted 

building exteriors adjacent to the roadway. Distracting lighting can also include that 

from fuel stations, automotive sales lots and other commercial development where 

lighting is used to attract attention to businesses.

− Intense: Would typically be areas with large advertising signs, sports lighting, and 

other intense light sources adjacent to the roadway. Intense sources can be found in 

both rural and urban areas.

• Area classification

• Distance from development to roadway

• Ambient Lighting

• Raised median curb

The worst-case rating factors (R) shall apply for the entire length of road being considered. The 

weighted value is high for ambient lighting.

4.3.4 Crash Factors (Night and Day)

In the warranting forms crash factors are included using the night-to-day crash ratio for the given

length of road to which the warrant is being applied. As the warrant point-score for this category 

is heavily based on night-to-day crash ratios, it is essential that detailed and well-defined crash

data be applied. Where crash ratios are not known, engineering judgment should be applied 

using crash statistics from similar roads where data is available.

Where a low number of crashes have been recorded (i.e., two at night, and one during the day), 

lighting may meet the warrant crash ratio; however, due to the low numbers it may be of less 

benefit than for other areas with similar ratios and higher numbers.
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34

Lighting is warranted where a total point-score of 60 or more is achieved. If the night-to-day 

crash ratio is 2:1 or greater, lighting is automatically warranted regardless of the overall pointscore. 

Lighting may be prioritized solely on the basis of the point-scores, or in conjunction with a 

benefit/cost analysis. Benefits would typically be based on the potential reduction in crash

frequency and severity. Depending on road authority practice, costs would typically include the 

Excerpt from the TAC Guide for the Design of 

Roadway lighting (27)
LIGHTING HANDBOOK

35

initial cost of the lighting system, its ongoing (electricity) costs, and its maintenance costs. 

Initial costs may be substantial if a power source is not present.

4.4 Warranting Method for Intersections

The Transportation Association of Canada Guide for the Design of Roadway Lighting includes a 

warranting system for intersection lighting. The warranting system is based on geometric, 

operational, environmental and crash factors. The critical factors determining the need for 

illumination are traffic volumes and night-time crashes. The warrant point score indicates 

whether full intersection lighting, partial lighting or delineation lighting is needed. Full 

intersection lighting denotes illumination covering an intersection in a uniform manner over the 

traveled portion of the roadway. Partial lighting is the illumination of key decision areas, 

potential conflict points, and/or hazards in and on the approach to an intersection. The 

illumination of vehicles on a cross street or median crossing, or lighting that marks an 

intersection location for approaching traffic, is referred to as sentry or delineation lighting.

The critical factors used to determine the need for illumination include the following:

• Traffic volumes (particularly on the cross street).

• The presence of crosswalks.

• Nighttime crashes that may be attributed to the lack of illumination.

• The extent of raised medians.

• Several secondary factors are also considered in the warrant, but are given less weight in the

overall point-score. In the warrant, traffic volumes and nighttime crashes are given greater

weight than raised medians, which can be designed, marked, or modified to reduce the risk

associated with its presence in the roadway.

The following terminology is used with respect to the amount of lighting, as determined by the 

warrant system:

• Full Lighting – Denotes lighting covering an intersection in a uniform manner over the 

traveled portion of the roadway.

• Partial Lighting – Denotes lighting of key decision areas, potential conflict points, and/or 

hazards in and on the approach to an intersection. Partial lighting may also guide a driver 

from one key point to the next, and (if sufficient luminaires are used) place the road user on a 

safe heading after leaving the lighted area.

• Delineation Lighting – Denotes lighting that marks an intersection location for approaching 

traffic, lights vehicles on a cross street or lights a median crossing.
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36

Based on the warrant analysis (the warranting form can be found in the TAC Guide for the 

Design of Roadway Lighting Document (27)), the following conditions define the need for full, 

partial or delineation lighting:

• If the intersection is signalized, full lighting is warranted.

• If the intersection is not signalized, the need for and the amount of lighting is indicated by 

comparing the point-score obtained from the warrant form categories to the following 

criteria:

− Full Lighting - Is warranted where a total point-score of 240 or more points.

− Partial Lightning - Is warranted where the point-score is between 151 and 239 points.

− Delineation Lighting - Is warranted where the point-score is between 120 and 150.

− No Lighting - Generally, a point-score under 120 indicates that lighting is not 

warranted. This score indicates that neither the critical operational warranting factor 

(substantial traffic volumes) nor the critical crash warranting factor (repeated 

nighttime crashes) is present.

Lighting may be prioritized solely on the basis of the point-scores, or in conjunction with a 

benefit/cost analysis. Benefits would typically be based on the potential reduction in crash

frequency and severity at the intersection. Depending on road authority practice, costs would 

typically include the initial cost of the lighting system, its ongoing (electricity) costs, and its 

maintenance costs. Initial costs may be substantial if a power source is not present at the 

intersection.

4.5 Other Examples of Intersection Warranting

Some authorities have looked at simple ways to prioritize lighting needs, particularly with rural 

intersections. Preston and Schoenecker (1999) (16) developed a system using traffic volumes on 

the major street by functional classification to give a priority to lighting intersections.

Major Street Functional Classification

Principal Arterial

(TH)

Minor Arterial

(TH or CSAH)

Collector

(CSAH or CR)

Local

(CR or TWN Rd)

Priority Major street volumes in vehicles per day

(% of major street volume that is recommended on the minor street)

Low 0-2000

(10%)

0-1000

(10%)

0-500

(10%)

0-250

(10%)

Moderate 2,000-5,000

(15%)

1,000-2,000

(15%)

500-1,000

(15%)

250-500

(15%)

High >5,000

(20%)

>2,000

(20%)

>1,000

(20%)

>500

(20%)

Figure 17 – Prioritization of Street Light Installations by Functional Class
LIGHTING HANDBOOK

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Lighting Impacts: General Considerations

Lighting provides the benefit of improving safety for motorists and pedestrians; however, it also 

has a larger impact on our nighttime environment. Ongoing research demonstrates the impact

of lighting at night as it relates to human health and to the condition of wildlife and plant life. 

As a result, revisions are being made in our approach to light control and recommended lighting 

levels. This research also affects the decision-making process on whether, and where, lighting is 

beneficial.

This section, which includes Chapter 5 – Considerations Concerning Lighting Systems and 

Chapter 6 – Lighting System Selection, discusses some general considerations regarding 

lighting impacts, and measures being taken to address them.
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5 Considerations Concerning 

Lighting Systems

5.1 Environmental Impacts

Nighttime lighting can impact humans, animals, and plants, 

both on and off the roadway. 

5.1.1 Light Trespass

Light trespass (obtrusive lighting) is defined by three major 

interrelated elements. The three elements are:

• Spill light: Light that falls outside the area intended to be 

lit. It is typically measured in lux in a the vertical plane 

with the light meter oriented towards the light source.

• Glare: Light that is viewed at the light source (luminaire), which reduces one’s visibility. 

Glare is further defined below. 

• Sky glow: Light reflected from the light source, road or other surfaces up into the 

atmosphere. Sky glow in effect reduces one’s ability to view stars in the night sky by casting 

unwanted light into the atmosphere. Though this is not a safety or security issue, groups such 

as the International Dark-sky Association (IDA) have mounted strong campaigns to reduce 

sky glow and protect visibility of our night sky. 

Figure 18 – Spill Lighting, Glare and Skyglow

The impact of 

lighting systems on 

the environment 

and abutters should 

be assessed in all 

roadway lighting 

designs
LIGHTING HANDBOOK

39

Figure 19 – Example of Skyglow

Maintaining an effective balance between the reduction of light trespass and the provision of 

quality, beneficial lighting requires thoughtful design and the selection of luminaires with cut-off 

or full cut-off optical systems. Lighting design with full cut-off optics will typically reduce 

skyglow and spill lighting. Moreover, it will reduce veiling luminance (glare) from the luminaire

on and off the roadway, thus improving overall visibility.

Figure 20 – Example of High Glare Street Lighting

Spill light levels have been developed and are documented in IESNA TM-11 Lighting Trespass: 

Research, Results and Recommendations and IESNA RP-33 Lighting for Exterior Environments. 

They are defined in the table below. Designations (LZ1 to LZ4) define the Light Zone and are 

further defined below. These levels are recommended by the IES where possible. They are

typically calculated and measured from the residential boundary line, but are sometimes

evaluated from the location of the residence being investigated.
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Figure 21 – Spill Light Levels

It is important to note that the reduction or elimination of light trespass must never take 

precedence over the provision of adequate roadway lighting. Lighting the area adjacent to 

roadway travel lanes (typically within or adjacent to the road right of way) can benefit a driver’s 

peripheral vision. This can also provide better visibility of crossroads, driveways, and sidewalks. 

Lighting the area adjacent to the road can also help in the detection of large animals that may 

pose a safety hazard. Balancing the needs of the road user with any potential impacts of the 

lighting system can be difficult for many roadway types, but the issue needs to be approached 

holistically.

5.1.2 Lighting Zone Definitions

Zoning is a well-established practice in community 

planning. The fundamental idea behind zoning is that it 

allows a community to determine and regulate appropriate 

types of use in different areas within its jurisdiction—that is, 

to define acceptable land uses. Lighting zones work well 

with land use zones in determining the type and amount of 

lighting that can be used in different areas. 

The choice of an appropriate lighting zone is a matter of 

judgment based on community priorities for any given area. 

Among the factors that must be considered are neighborhood 

ambient conditions, lighting expectations, special environmental concerns, and how interior 

lighting may affect the exterior environment. 

Because identifying the appropriate outdoor lighting zone is a matter of judgment and consensus, 

there is no automatic means of determining which zone is appropriate for a given area. The same 

Lighting zones do not 

correspond with land 

use zones. They 

should be applied with 

engineering judgment 

for specific project 

conditions
LIGHTING HANDBOOK

41

type of lighting application may fall into different lighting zones in different jurisdictions.

According to the IESNA Lighting Handbook, the lighting zones are defined as:

5.1.2.1 LZ1 Zone – Low Ambient Lighting

Areas where lighting might adversely affect flora and fauna or disturb the character of the area. 

The vision of human residents and users is adapted to low light levels. Lighting may be used for 

safety and convenience but it is not necessarily uniform or continuous. After curfew, most 

lighting should be extinguished or reduced as activity levels decline.

5.1.2.2 LZ2 Zone - Moderate Ambient Lighting

Areas of human activity where the vision of human residents and users is adapted to moderate 

light levels. Lighting may typically be used for safety and convenience but it is not necessarily 

uniform or continuous. After curfew, lighting may be extinguished or reduced as activity levels 

decline. 

5.1.2.3 LZ3 Zone Moderately High Ambient Lighting

Areas of human activity where the vision of human residents and users is adapted to moderately 

high light levels. Lighting is generally desired for safety, security and/or convenience and it is 

often uniform and/or continuous. After curfew, lighting may be extinguished or reduced in most 

areas as activity levels decline.

5.1.2.4 LZ4 Zone - High Ambient Lighting

Areas of human activity where the vision of human residents and users is adapted to high light 

levels. Lighting is generally considered necessary for safety, security and/or convenience and it 

is mostly uniform and/or continuous. After curfew, lighting may be extinguished or reduced in 

some areas as activity levels decline.

5.1.3 Glare

Bright sources of light in the visual field create glare. Light is scattered in the human eye, 

resulting in a phenomenon known as “veiling luminance.” This results in a visual haze within 

the eye, reducing visibility. Veiling luminance that occurs when bright oncoming headlights 

significantly reduce one's vision is a common experience. Blocking the bright source or looking 

away from the visual field reduces the haze associated with veiling luminance, and vision is 

partially restored. 
LIGHTING HANDBOOK

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Figure 22 – Example of Glare

The perception of glare, however, varies greatly between observers. The IESNA define glare as 

“the sensation produced by luminances within the visual field that are sufficiently greater than 

the luminance to which the eyes are adapted, which causes annoyance, discomfort, or loss in 

visual performance and visibility. The magnitude of the sensation of glare depends on such 

factors as the size, position, and luminance of a source, the number of sources, and the luminance 

to which the eyes are adapted.”

Glare typically falls into one of the following categories:

• Disability Glare: The presence of an amount of glare so significant as to prevent an 

individual from seeing adequately. An example of disability glare is a driver’s substantially 

reduced visibility caused by the headlights of an oncoming car.

• Discomfort Glare: The presence of glare that may over time causes a sense of pain or 

annoyance, and may increase blink rate or even cause tears. 

Disability and discomfort glare are very different phenomena. Disability glare depends on the 

quantity of light falling on the eye and the angle from the line of sight. With discomfort glare the 

source luminance is a major factor; with disability glare the source intensity is a major factor.

Typically, disability glare will apply to drivers on the roadway, and a numerical ratio has been 

developed referred to as the veiling luminance ratio which is applied to lighting design as part of 

IESNA RP-8. Veiling luminance is therefore a key criterion in undertaking lighting design. The 

effect of veiling luminance on visibility reduction is dependent upon the average lighting level, 

or average luminance level, of the pavement. A higher level of veiling luminance can be 

tolerated if the pavement luminance is high. Veiling luminance is calculated in terms of a ratio 

of the maximum veiling luminance experienced by the observer to the average pavement 

luminance.

IESNA TM-11 Lighting Trespass: Research, Results and Recommendations observes: “Source 

brightness had been generally identified as being the principal characteristic to which persons 

object. Spill light was seen as a less significant effect. It was decided, therefore, to design 

experimentation to identify quantitatively the relationship between source brightness and the 
LIGHTING HANDBOOK

43

degree to which the light source was found objectionable.” Source intensity is a published 

method of evaluating the off-site discomfort glare. CIE has also produced a document (CIE 

150:2003 Guide on the Limitation of the Effects of Obtrusive Light from Outdoor Lighting 

Installations) that defines limitations for source brightness (intensity) and spill light for outdoor 

lighting applications. Figure 23 defines source intensity levels. This method will typically be 

applied where high-wattage light sources such as flood lighting or high mast lights are used. The 

environmental zone E1-E4 correspond to the lighting zones LZ1-LZ4 described in section 5.1.2.

Figure 23 – Source Intensity Levels

From the perspective of limiting the impact of a lighting system to both on- and off -road 

observers, a lighting system meeting the disability glare requirements of AASHTO and IES 

generally provides the needed control.

5.1.4 Animal and Plant Impacts

Lighting can have impacts on animals as well as humans, particularly since a good deal of 

animal activity takes place at night. Almost all small rodents and carnivores, 80 percent of 

marsupials, and 20 percent of primates are nocturnal. Lighting in environmentally sensitive 

areas with animal activity should minimize the duration, direct the light only where needed, and

reduce intensity as much as possible. An example of the impact of lighting on wildlife can be 

found along the southern Atlantic coast of the United States. Sea turtle hatchlings in this area are 

genetically programmed to use starlight and moonlight reflections off the water to guide them 

from their nest to the water. However, man-made light sources can confuse the hatchlings and 

lead them inland, away from the ocean and on to lighted roadways. Local codes in this region 

may require the use of full cut-off light sources, controls, and other limitations on exterior 

nighttime lighting. Another impact to wildlife is the potential for bird strikes to illuminated 

structures, particularly when they are located along migration routes.

Plants have evolved a wide range of photoreceptors that perceive and respond to light signals in 

the ultraviolet, blue, red, and near-infrared regions of the electromagnetic spectrum. While there 

is not a significant body of research to explore and document the specific effects of electric 

lighting on plant life, there is little doubt that plants are affected in some degree by lighting.
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5.1.5 Human Health Impacts

Since the beginning of the 1980’s the effect of light on human performance and health has been a 

point of discussion and research. Disruptions to our circadian rhythms, the pattern of behavioral 

and physical processes including hormone secretion which is very dependent on light-dark 

cycles, has been linked to an increased risk to hormone dependent cancers such as breast and 

prostate cancer (Bartsch et al., 1985) (17). Bartsch also concluded that “melatonin controls not 

only the growth of well differentiated cancers, but also possesses anti-carcinogenic properties.”

Research shows artificial lighting at night could also suppress melatonin (using 2500 lux of 

white light for between 2 to 4 hours). 

The hormones responsible for the circadian rhythm in humans are melatonin, which is released 

in response to increasing levels of darkness and which promotes sleep, and cortisol, which is the 

biological opposite of melatonin and an indicator of the level of human activeness. 

From an exterior lighting perspective, the question is whether levels and/or certain types of 

lighting can cause the suppression of melatonin levels at night through light trespass, producing a 

negative impact on the health of residents. The spectrum of the light can also have an influence,

with shorter wavelength lighting having more of an impact. The amount of light needed has to 

be of sufficient level and applied for a sufficient amount of time to have an effect on melatonin 

levels. 

Research reported in the Journal of Carcinogenesis (18) regarding the impact of light at night on 

residents from street lighting systems notes: “These light levels rarely exceed 10 lux at the 

cornea outdoors. Indoors, behind closed curtains, the levels would likely to be much lower. 

Further, the human eyelids transmit only about 1% to 3% in the short wavelength region of the 

visible spectrum....Given the available published data on human melatonin suppression in 

response to light, light trespass through residential windows is an unlikely cause of melatonin 

suppression, simply because the light levels are so low, particularly with the eyes closed.”

Research into these topics is ongoing and not yet conclusive. Thresholds for these non-visual 

effects are not clearly established at this time. The complexities and interactions, along with the 

long-term aspects of these issues, make definitive statements elusive.

5.2 Lighting Impacts on the Aging Population

As we age, we are more susceptible to glare. Diseases such as glaucoma can also reduce 

peripheral vision. This is significant as our population ages and as life expectancy continues to 

increase. As we age, our eyes deteriorate considerably in their ability to adjust the pupil opening 

in proportion to the available light. The eye gate becomes smaller and smaller even in the 

daytime, but the critical feature is the inability to open up at twilight and in darkness to let in

whatever little light might be available, particularly past the age of 60 (19).
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Figure 24 - Reduction in Visibility Level with Age

A vital factor is the ability to see the movement of objects that may represent a hazard from the 

corner of the eye. It has been found that the ability to see movement 40 and 80 degrees away 

from the line of sight is reduced as much as 60 percent for people over 60 (19). A younger 

person can typically see to some degree even with very little light, but this sensitivity to low 

brightness is reduced to approximately one half at 80+ 

years of age (19). It has been found that it can take up to 30 

minutes for an 85-year-old person to adapt to lower outdoor 

night- time brightness after having been adapted to the 

higher interior brightness (19). This long period of eye 

adaptation can be greatly reduced with roadway lighting. 

The visibility factors noted above also apply to pedestrians. 

Reduced visibility reduces pedestrians’ ability to see motor 

vehicles and avoid crashes. This increases the risk that 

already exists due to the fact that reaction speed for both 

the driver and pedestrian is reduced with age.

Installations 

expecting an 

increased use by 

older drivers may 

consider increasing 

lighting levels 

and/or reducing 

glare
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Figure 25 - Effect of Aging on the Human Eye

Figure 25 shows the effect aging has on the human eye. As we grow older, the lens becomes 

discolored (darkens), thus reducing visibility.

Older drivers are also more susceptible to glare. Figure 26 shows that the amount of contrast 

needed to overcome the driver threshold contrast increases significantly with age. At a light 

level of 0.5 cd/m2 a 65-year-old driver needs approximately 10 percent more contrast to be able

to see an object.
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Figure 26 - Impact of Glare and Light Level on the Visibility of Aging Drivers

We do not currently design roadway lighting system with modifiers for age. A designer or 

agency, however, should be cognizant of the differences between younger and older drivers and 

may want to consider modifications, either a reduction in the amount of glare or an increase in 

the lighting levels, if the majority of the road users will be elderly.
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6 Lighting System Selection

6.1 Design Considerations

In some cases, site conditions may dictate if roadway 

lighting can be installed, or may place certain constraints 

on the design. Therefore, the following site conditions 

should be investigated:

• Availability of Power – The availability of power is a 

major factor in determining if roadway lighting can be 

provided. If power is not available, the local utility 

should be consulted and cost estimates for power 

supply should be determined.

• Proximity to Aircraft Landing Facilities – Prospective 

installations in close proximity to airports and 

helicopter landing pads may pose problems with 

defined glide paths and air traffic control operations. 

Typically, an airport authority or their governing authority will have specific pole height 

limitations and/or optical requirements for the luminaires. Where a lighting installation is 

proposed in close proximity to an aircraft landing facility, the facility should be contacted so 

requirements specific to that facility can be met.

• Proximity to Railroads – Lighting systems near railroad tracks will have specific clearance

requirements from the tracks. 

• Presence of Overhead Distribution and Transmission Lines – Distribution and transmission

lines often conflict with lighting poles. Where transmission or distribution lines exist, or are

proposed, and lighting is required, the designer should consult the local utility provider and

investigate applicable codes and standards to determine clearance requirements. Typically 

the higher the voltage of the overhead lines, the greater the clearance distance required. In 

the case of overhead transmission lines, the local electrical utility may define additional 

clearance requirements due to the potential sag of the transmission lines. Line sag will vary 

with the change in ambient temperature and power demand.

• Environmental Issues – The presence of offsite glare, light trespass and skyglow should be 

taken into consideration in urban areas. The designer should consider these issues prior to 

undertaking any design and be aware of community concerns and local requirements. Local 

lighting ordinances may also dictate the type of lighting which may be installed, and may 

dictate light trespass and skyglow limits.

• Maintenance and Operations Considerations – Maintenance should be considered as part of 

the roadway lighting design. Where possible, maintenance personnel should be consulted by 

those undertaking the roadway lighting design. In some cases, products with a higher initial 

purchase cost can significantly reduce operating or maintenance costs over the life of the 

project. Products specified should be both corrosion-resistant and durable. All luminaires will 

require regular service for lamp replacement and cleaning. It is critical that the luminaires be 

safely accessible via available service vehicles (used by those undertaking the maintenance) 

Lighting designs 

need to be 

performed in full 

coordination with 

the features of 

roadway and 

surrounds
LIGHTING HANDBOOK

49

with minimal disruption to traffic. The height limits of maintenance equipment may impact 

pole height and location.

• Roadside Safety Considerations – Poles can be a potential hazard to errant motor vehicles.

Clear zones and pole placement issues should be known and addressed. Additional 

information can be found in the AASHTO Roadside Design Guide.

• Historical Safety Performance – It is recommended that historical crash data be reviewed in 

an effort to identify what may be problematic crash 

locations. This can be done by first driving, walking or 

cycling the road and establishing possible problematic 

locations. Municipal agencies, road authorities and 

maintenance contractors can be contacted to confirm 

whether these locations have any recorded crash

statistics. Problem areas should be identified and 

solutions discussed with the owner.

6.2 Lighting Selection

A key task for the roadway lighting designer is the 

selection and specification of products and equipment. Many manufacturers produce outdoor 

lighting equipment that is marketed and available throughout North America.

The use of high quality products is critical to prolonging the overall operating life of roadway 

lighting systems. Quality relates to the features and characteristics of a product that impact on its 

ability to satisfy stated or implied needs. While quality could be overlooked if low price is the 

primary criterion for product selection, it should always be a key consideration in product 

selection. In general, focusing on price alone will not deliver best value installations.

In addition to quality, other key considerations when specifying a product include:

• Certification – Electrical products must be certified by an organization accredited by the 

Standards Council of Canada, and shall bear an appropriate label such as Underwriters’ 

Laboratories (UL).

• Photometric Performance (for luminaires) – A photometric comparison of luminaires is 

critical to selecting the best product for a given application. Cobra head luminaries can be 

compared using the CSA 653 model. Comparisons should be based on photometric data 

provided by the supplier from an independent testing laboratory. The IESNA cutoff 

classification for luminaires should be known and deemed appropriate for the situation. In 

general, cutoff or full-cutoff optics should be used wherever possible. 

• Durability – Durability is the capability of a product to resist deterioration, damage, and 

corrosion over time. Designers should understand the potential for vandalism and the 

corrosive nature of the project’s environment, and relate those variables to the specific 

products under consideration.

• Aesthetics – Products selected should be aesthetically compatible with their surroundings. 

Manufacturers offer a wide range of equipment with respect to shape, configuration, colors, 

and styles. Similar or identical-looking products should be used, if possible, when the new 

Lighting systems 

should be selected 

based on the most 

beneficial life cycle 

cost of the system
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installation will be integrated with existing installations. The height of lighting structures 

should be visually compatible with the height of other structures in the area.

• Availability – Custom and/or decorative products or products manufactured in small 

quantities often have long lead times for replacement. Designers should verify that the 

products selected will be available to avoid construction schedule impacts. Also, they should 

confirm that parts or complete replacement units will be available following installation. If 

products or parts will not be readily available, the designer should advise the owner to 

consider purchasing replacement units or parts to stock for maintenance purposes.

• Maintenance Requirements – Maintenance considerations include ease of access for 

servicing, as well as maintenance frequency and level of service required over the product’s 

anticipated useful life.

• Operations Cost – Similar products can result in varying cost of operations. This is 

particularly true of products that consume energy. The designer should review operational 

costs when specifying products and choose those products that are both economical to 

operate and provide the required performance.

The capital cost of an item (also known as the supply cost) is not listed above but is also an 

important consideration. Supply costs, however, should not be the primary factor when selecting 

products. To assess a product’s true cost, other factors must be considered to confirm best value 

and performance, or life cycle of a product.

Whenever possible, individuals specifying products are encouraged to designate more than one 

manufacturer with similar or equal products to reduce costs via competitive bidding. All 

products proposed, however, should be reviewed for conformance to stated specifications and 

performance requirements. In some cases a specific product or manufacturer may need to be 

sole sourced because of the product’s enhanced performance, special appearance, or the need to 

match existing adjacent conditions.

Specific luminaire requirements are as follows:

• Ingress Protection (IP) Rating - Optical systems should be well sealed to prevent the entry of 

dust and water. Luminaires should have an IP rating of 65 or 66 for maximum performance.

• Lens Material - Lenses should be composed of glass. Polycarbonate and acrylic materials, 

though more impact-resistant, tend to discolor over time, which will reduce light output and 

will often require replacement in about 5 years.

• Housing - The housing should be made of aluminum with a powder coat exterior finish. The 

luminaire should be designed for secure attachment to the pole. The luminaire should be 

designed for easy access for electrical and lamp changes via a tool-less entry

• Internal Electrical - Internal components will include a ballast, a starter and, a capacitor. The 

ballast should be a constant wattage auto-transformer (CWA) type.

• BUG Ratings – The luminaire optics should meet the specific BUG ratings where they are 

available. 
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6.3 Luminaire Classification

To assess and mitigate glare and to reduce skyglow, the IESNA have developed cut-off 

classifications for luminaries based on how they emit light. 

The amount of glare generated by a luminaire is strongly influenced by the intensity 

(candlepower) emitted at angles close to the horizontal. 

6.3.1 Luminaire Classification System

A new method referred to as the Luminaire Classification System (LCS) has been developed to 

define luminaire distribution and efficiency better. IESNA TM-15 Luminaire Classification 

System for Outdoor Luminaires defines this system in more detail. The LCS replaces the 

traditional IESNA luminaire cutoff classification system which uses designations like cutoff, 

non-off, semi-cutoff, and full cut-off. The traditional system was very limited as it only assessed 

the light distribution at very high angles and above horizontal.

The LCS defines a method of evaluation and comparison of outdoor luminaires. It provides a 

basic model which defines maximum lumens within defined angles within primary areas. The 

primary LCS areas are forward light, back light, and up-light zones as defined in Figure 27 (top 

left). Each of these zones is further broken into solid angles within the area. An example of the 

forward light zone is shown in Figure 27 (top right). 

The sum of percentages of lamp lumens within these three primary areas is equal to the 

photometric luminaire efficiency. The LCS enables designers to evaluate and compare the 

distribution of lumens for various types of luminaire optics, thus assisting in the selection of the 

luminaire most appropriate for the application. An example of measurements for various 

luminaires is defined in Figure 28.

The benefit of this system, is that it allows a designer to better select the optimal optics for a 

given application while at the same time reducing light trespass impacts and sky glow. The new 

classification system is intended to be used as a tool to assess the light output of luminaires.
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Figure 27 - Lamp Lumen Zones and Front Light Zone (from IESNA TM-15)

The LCS zones for various luminaire optical systems are calculated and shown in Figure 28.

Through lighting photometric analysis software, a designer can use the LCS assess the 

percentage of lumen output in the various zones. This is very useful when comparing luminaire 

optical systems and how light is distributed from various luminaries. 
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Figure 28 – LCS Comparison (IES TM-15-07)

6.3.2 BUG Rating System

Similar to the LCS, the IESNA developed the Backlight-Up-light-Glare (BUG) rating system 

which establishes back (B), up-light (U), and glare (G) zonal lumen limits for luminaires. 

Each category (backlight, up-light, and glare) consists of specific regions that surround the 

luminaire. Each region has specific upper limit criteria that must be met to obtain the rating. All 

of the criteria must be met for a luminaire to obtain the generalized B, U, or G rating. So, the 

rating for a specific metric is set by the lowest (highest zonal lumen value) performance criterion 

within the metric. The limits vary according to the lighting zone (LZ1 – LZ4) in which the 

luminaire is located.

Metal Halide

Internal 

Refractor 

Optic (250 

W Type V)

External 

Refractor 

Optic (250 

W Type V)

Louvered 

Reflector 

Optics (250 

W Type III)

Hydroformed 

Refractor 

Optics with 

Horizontal 

Lamp (250 

W Type I)

Sag Lens 

Refractor 

Optics (250 

W Type III)

Sag Lens 

Refractor 

Optics (250 

W Type I)

Sag Lens 

Refractor 

Optics (100 

W Type I)

Forward Light

Luminaire Lumens 4133.4 5405.6 6306.5 6487.6 10115.6 10557.0 3716.3

% Lamp Lumens 19.70% 25.70% 30.00% 29.50% 46.00% 48.00% 45.90%

FL (0 ̊-30 ̊) 0.20% 0.90% 1.20% 2.40% 7.40% 13.10% 12.60%

FM (30 ̊-60 ̊) 5.40% 3.70% 14.40% 15.30% 27.20% 24.80% 23.40%

FH (60 ̊-80 ̊) 8.90% 17.30% 12.90% 11.20% 11.20% 10.00% 9.60%

FVH (80 ̊-90 ̊) 5.10% 3.80% 1.40% 0.50% 0.20% 0.10% 0.20%

Back Light

Luminaire Lumens 4133.4 5352.5 4220.2 4880.5 5384.3 7138.1 2465.6

% Lamp Lumens 19.70% 25.50% 20.10% 22.20% 24.50% 32.40% 30.40%

BL (0 ̊-30 ̊) 0.20% 0.90% 0.80% 2.30% 5.40% 7.70% 7.20%

BM (30 ̊-60 ̊) 5.40% 3.60% 9.40% 13.20% 14.50% 17.00% 16.10%

BH (60 ̊-80 ̊) 8.90% 17.10% 8.80% 6.00% 4.40% 7.60% 7.00%

BVH (80 ̊-90 ̊) 5.10% 3.90% 1.00% 0.70% 0.10% 0.10% 0.10%

Up-light

Luminaire Lumens 9997.6 2477.0 957.5 163.2 0.0 0.0 0.0

% Lamp Lumens 47.60% 11.80% 4.60% 0.70% 0.00% 0.00% 0.00%

UL (90 ̊-100 ̊) 10.70% 2.40% 1.40% 0.50% 0.00% 0.00% 0.00%

UH (100 ̊-180 ̊) 37.00% 9.40% 3.20% 0.20% 0.00% 0.00% 0.00%
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Once this calculation is performed for each of the three metrics, the composite BUG rating can 

be reported. Forward, Back and Up-light Zones and Forward Light Zones show the BUG 

regions. Solid angle references are based on a sphere of data points around a luminaire.

Figure 29 – Bug Zones (IES TM-15-07)

Backlight considers the light leaving a luminaire in the opposite direction from the main aiming 

angle of the light. This is the percent lamp lumens or the luminaire lumens distributed behind a 

luminaire between 0o vertical (nadir) and 90o vertical. Within a lighting zone, the backlight 

rating will change depending on the luminaire’s proximity to the property line. Backlight is 

evaluated for high (60o–80o), medium (30o–60o) and low (0o–30o) areas.

Figure 30 – BUG Backlight (IES TM-15-07)
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Up-light measures the total light propagating from the luminaire in a near-horizontal or abovehorizontal direction. This is an overall measure of the amount of light directly leaving the 

luminaire that may be associated with sky-glow. This measures the percent lamp lumens or the 

luminaire lumens distributed above a luminaire between 90o and 180o vertical. Up-light is 

evaluated for high (sky-glow: 100o–180o), low (90o–100o), forward light very high (80o–90o), and 

backlight very high (80o–90o).

Glare considers the light leaving a luminaire in the angles that are most likely to be a source of 

nuisance (or potentially disabling) to passers-by either within or outside the property boundaries. 

The light that causes glare is also sometimes presumed to be a source of light trespass problems. 

However, in most cases, glare complaints are due to the brightness of the source, and not because 

of spill light levels. For this reason, it is treated separately from the Backlight metric . Glare is 

evaluated for forward light very high and backlight very high (80o–90o), forward light medium 

(60o–80o), and backlight medium (60o–80o).

Note that the Up-light and Glare regions overlap as do the Glare and Backlight regions. While 

Glare is generally only considered important up to horizontal, the Up-light region has been 

shown to be important below horizontal, down to about 80°. Since these criteria regions are not 

intended to be additive or comprehensive to the complete output of the luminaire, this overlap is 

not a calculation inconsistency.

The region from directly below the luminaire forward to 60° is not considered in any of the 

criteria regions. This region is generally considered the ‘safe’ region of lumen output, where the 

light from a luminaire will be falling on the task area in an effective manner, and is also the 

region where the majority of lumens are outputted. Beyond this unmeasured region, the light 

may begin to be a source of glare, light trespass, sky-glow, or other concerns.

6.4 Lighting Master Plans

Lighting master plans are formal documents created through a study and planning process. They 

are based on input from municipal staff, public officials, lighting professionals, citizens, business 

owners, and others. Lighting master plans define the purpose of lighting, and contain area maps 

with road types, classifications, land use, pedestrian and cyclist routes, parks, and other

infrastructure information. They also contain information regarding fixtures and poles, light

sources, fixture cutoff, lighting levels, design criteria, design and construction specifications,

historical considerations and recommendations. This information is combined in a single, 

organized package that becomes the basis for lighting projects. 

Lighting master plans take into account anticipated economic and cultural changes, a

community’s public image and economic development goals, and technological advancements.

The benefits of such plans include the coordination of the various municipal lighting functions, 

proactively planning lighting for the different areas of a community by recognizing their unique 

character and needs. The plans also provide scheduling of capital expenditures, as well as 

implementation and maintenance strategies. Lighting master plans are based on the core concept 

that public facilities should enhance safety, encourage economics, contribute to beautification, 

and provide a secure environment for people and property. Transportation-related lighting is 

viewed as a key component of community management.
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Lighting master plans are typically adopted by a jurisdiction through a bylaw, resolution, or 

similar measure, and as such may dictate specific design requirements for roadway lighting. The

purpose of a lighting master plan is to ensure adequate lighting is provided for future 

development, and that public lighting will be installed in a consistent manner that takes into 

account the needs and desires of citizens. If an area is designated for historic preservation, the 

lighting master plan may define luminaires and light sources that are compatible with and 

preserve the area’s historical character, or that enhance the existing historical character.

Lighting master plans typically address the following major subject areas:

• Improved safety provided by lighting.

• Improved sense of security provided by lighting.

• Costs (capital and operating).

• Aesthetics (daytime and nighttime).

• Lighting design criteria.

• Environmental issues and constraints, including the control of spill light, glare and skyglow.

• Energy use (through definition of unit power density).

• Potential for economic development and the enhancement of nighttime activities through

lighting

• Preservation of areas of darkness, such as areas around observatories.

• Maintenance requirements.

Designers should check with local officials prior to beginning the design process to determine if 

a lighting master plan is in place, or is anticipated. Designers should be aware of the 

requirements of lighting master plans as they relate to the specific project under consideration. 

At the same time, under no circumstances should lighting master plan requirements dictate the 

quantity or quality of light for a roadway facility, since the safety of the roadway user is of 

paramount importance.
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Lighting Application Considerations

AASHTO and IES provide recommendations for light levels and other considerations relating to 

roadway lighting. This section discusses additional considerations, including design and 

calculations guidance, which may assist in proper evaluation and installation of lighting 

systems.
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7 Lighting Application

7.1 System Layout and Geometry

The lighting industry has defined standard pole spacing layout designations. These standard

pole spacing layout designations are one-sided lighting, opposite lighting, staggered lighting,

and median lighting. 

Figure 31 – Typical Pole Spacing

Typically, one-sided spacing is used on roadways with one to three lanes, staggered spacing is 

typically used on roadways with three to six lanes, and opposite spacing is typically used on 

roadways with five or more lanes. Median lighting is typically used where the median is wide 

enough to accommodate poles and meet clear zone requirements, or where the poles are 

protected by barriers. From a capital cost perspective, median lighting may be very costeffective as the number of poles required may be reduced by 50 percent as opposed to opposite 

lighting. However, median lighting may cost more to maintain.
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Figure 32 – Pole Spacing

To lay out poles, the designer must undertake lighting calculations to define optimal pole 

spacing. Once maximum pole spacing is defined, one can lay out poles on the road drawings 

using a calculator and scale rule. The design should lay out poles locating a pole at a start points 

such as cross street, then spacing the poles evenly within the maximum pole spacing defined by 

the calculations, as shown in Figure 32. The pole spacing may need to be adjusted to suit 

driveways and utility conflicts. 
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Figure 33 - Highmast Pole Spacing

For highmast lighting, the lighting calculation process is slightly different than it is for a typical 

roadway. It is recommended that the designer develop lighting templates for a variety of 

highmast pole arrangements using various fixture quantities and distributions. This can be 

accomplished using various combinations of individual luminaries clustered on a given pole to 

create the most effective overall distribution of light through trial

and adjustment. By combining efficient templates, the designer is able to produce optimal light 

distribution for the given road geometry. The variables will include mounting height, number of 

luminaires, optics, and orientation of optics, wattage, light source, and photometrics.

The templates will show the pole location with luminance or illuminance levels using contour 

lines. The contour lines should represent different levels of illuminance or luminance. 

Typically, templates are developed in asymmetrical (long and narrow) or symmetrical (circular) 

patterns to suit road geometrics. The templates should be arranged on the site plan to show 

approximate pole locations, either digitally in a computer aided design (CAD) program as shown 

in Figure 33. 
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61

This method will give a rough pole layout and allow for optimization through trial and 

adjustment. Once the pole locations and pole distributions have been optimized, a lighting 

calculation should be undertaken for the entire interchange, defining lighting levels on the 

roadway. The lighting calculations will require further refinement, using trial and adjustment, 

until the desired levels are achieved. Highmast design will require many calculations

and trial and adjustment cycles to provide an optimized design.

7.2 Scale and Inter-Relational Design

When determining pole heights, types, and luminaire wattages, the designer must consider the 

land use (residential, urban, downtown, commercial, industrial, etc.) and the road width. Pole

height may also be limited by the reach of service vehicles used to maintain the lights. There is 

no exact formula for determining the optimal pole height and luminaire wattage for a given road. 

Factors such as pole spacing (one-sided, median, opposite, or staggered), luminaire photometrics, 

wattage, road geometrics, power line conflicts, lighting levels and uniformity, aesthetics, and 

obtrusive lighting issues are all appropriate considerations in defining optimal mounting height.

In residential areas, the designer should select pole heights and fixture wattages to reduce spill 

light levels to those suitable for the lighting environmental zone (LEZ).

Determination of pole height and luminaire wattage is made using computer lighting design

software to test different scenarios by a “trial and adjustment” process. Today’s computer

lighting software allows a designer to undertake calculations in minutes, thus allowing the

designer to explore many more options than were practical in the past. For an interchange,

highmast lighting may prove to be more effective than conventional davit-style, mast-arm or

truss-style lighting. In a downtown area, post-top lighting with a mounting height of 6.0 m or

less may be preferred to provide lighting structures with a more human scale, meeting the

requirement for improved aesthetics. For freeway ramps, intersections or a typical city roadway,

davit-style, mast-arm or truss-style lighting may prove to be the most effective.
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Figure 34 - Typical Lighting (Post-top and Highmast)

7.3 Adaptive Lighting

The need to reduce power consumption has stimulated significant research and product 

development in the field of roadway lighting. Adaptive lighting controls allow lighting levels to 

be reduced during off-peak periods. Simply put, a significant amount of power can be saved by 

varying the levels of lighting between peak and non-peak periods.

Lighting levels are established by applying criteria based on road classification (arterial, local, 

collector), type of pavement, pedestrian activity/conflict level. The higher the level of pedestrian 

conflict, the higher the level of lighting recommended. The present design practice is to use the 

highest pedestrian conflict/activity level for an area or segment of roadway to establish the 

minimum lighting levels for the portion of roadway under consideration. Once the minimum 

level of lighting is established, street lights have traditionally provided that level of lighting 

throughout the hours of darkness as adaptive technologies have been unavailable.

Pedestrian conflict levels do not necessarily remain constant throughout the hours of darkness, 

and in most instances the numbers of pedestrians present in a given area will be reduced in the 

late night and early morning hours when businesses are closed. Numbers of nighttime 

pedestrians may also be reduced based on the days of the week (weekday vs. weekend), seasonal 

factors, and other predictable dynamics. During hours of reduced pedestrian conflict, the level of 
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lighting provided can be reduced and while meeting recommended criteria for the actual level of 

pedestrians present. 

The amount of energy saving an adaptive lighting technology can provide depends on the 

variance of pedestrian conflict levels throughout the hours of darkness. During hours of reduced 

pedestrian conflict/activity, the level of lighting provided could be reduced (with reduced energy 

consumption) to the recommended criteria for the actual level of pedestrians present. An 

adaptive technology should not affect the distribution pattern of the luminaire, uniformity ratios 

are preserved, even with reductions in luminaire output. The reduction of lighting levels on 

local, collector and major roads can go from a high conflict to medium to low depending on 

predicted pedestrian activity anticipated during the course of the evening. In some cases where 

conflict has been designed to medium level then only a single to a low conflict/activity can be 

achieved. Where lighting is designed to a low pedestrian conflict then the recommended should 

be maintained to below those recommended.

Typically, the light output of the luminaire and lamp depreciates over their useful life, so 

designers must provide an initial level of lighting higher than the minimum maintained level. 

This compensation is achieved by applying a lighting loss factor to a lighting design. One of the 

components of light loss factor is lamp lumen depreciation, which defined based on lamp 

suppliers’ published curves at the anticipated end of lamp life. This factor is typically 10 percent

to 30 percent depending on the lamp type. Application of an adaptive technology may allow the 

street light to operate at its maintained level for the entire maintenance cycle, thus reducing 

power input and saving energy. One would not apply lumen depreciation to a lighting design, as 

the adaptive system would adjust the lamp output to maintain constant illumination on the 

roadway. 

Because lamp wattages are fixed, some areas served by street lighting are over-lighted to meet 

uniformity criteria, which is the driving factor in luminaire spacing. This may be the result of 

the lack of a lamp in the appropriate wattage (e.g., the design requires a 160-watt lamp, which is 

not available so a 200-watt lamp is used), or because an owner has standardized a particular 

pole/luminaire combination for maintenance purposes. Many roads are in fact lighted to well 

above recommended levels. Examples are local, collector or arterial roads where lighting levels 

are higher than required to meet uniformity requirement. An adaptive system could be used to 

rectify this issue as well as reduce levels during off peak.

Variation of lighting levels is not recommended in all lighting scenarios. Listed below are 

scenarios where reducing lighting levels in off-peak periods is not recommended: 

• Signalized Intersections - Signalized intersections typically include pedestrian crossings. 

Pedestrian conflicts with vehicles are very likely at signalized intersections even during lowpedestrian conflict periods. 

• Mid-Block Crosswalks - The same rationale used for signalized intersections applies.

• Roundabouts - Due to the geometry in roundabouts and the effectiveness of fixed headlights 

within the roundabout circle, dimming should not be applied to these facilities. 
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• Rail Crossings - Rail crossing lighting is provided for detection of the trains and is not related 

to pedestrian conflict levels, therefore reducing lighting during off-peak periods is not 

recommended.

Engineering expertise is required in the application of an adaptive technology. Experienced 

roadway lighting designers will be able to assist owners in choosing the sites best suited for the 

technology. An adaptive technology is not for all roads and should be reviewed in accordance 

with the recommendations of IESNA RP-8 or TAC. Prior to installing an adaptive technology it 

is recommended a feasibility study be undertaken. The following should be included:

• Development of Design Criteria - The designer would establish design criteria for the 

municipality or agency for the proper application of dimming in line with standard practice.

• Inventory of Existing Facilities - An inventory of existing facilities will be required,

including pole spacing, roadway classifications, pedestrian conflict levels, existing lighting 

levels and uniformities, configurations, etc.

• Undertake Computer Lighting Calculations - The engineer would provide calculations 

necessary to establish the applicability of dimming.

• Development of Cost Benefit Analysis - The engineer would assist the municipality or 

agency to develop and analyze the cost and benefits available.

• Development of Options and Rationale for Replacement or Retrofit of Luminaires - If 

existing luminaires are being retrofitted with the dimming technology, the engineer would 

establish criteria for evaluating where a new luminaire should be considered. Issues to be 

addressed would include age, condition, cost-effectiveness, etc.

• Verification and Testing - The engineer would provide independent verification of the 

performance of the dimming system.

• Master Planning (Recommended) to Optimize the Application of Dimming - Because 

communities and roadway networks are unique and operationally specific to an area, 

development of a dimming master plan is recommended. The master plan would define how 

dimming would be applied, and coordinate the retrofit of existing systems and new 

installations. In general, the application of dimming to new installations (new roadways or 

new lighting in conjunction with roadway improvements) should be prioritized to take 

advantage of energy savings, while retrofitting existing lighting may depend on a number of 

factors.

• Agreement Between Owner and Utility Companies Will Be Required - As most street 

lighting in North America is unmetered, an agreement between the utility company and the 

owner will normally be required for the owner to receive the monetary benefit associated 

with adaptive lighting.

An effective way to control lighting is via an adaptive lighting system. Adaptive lighting control 

systems can control, monitor and record the operating status of luminaires in a lighting system

from a remote location using a desktop computer via the internet. Adaptive systems typically 

use miniature solid-state control devices that are installed in each new or existing luminaire. 

These systems are typically designed with software to allow an owner to build a database of the 

asset and monitor performance on an area-wide basis.
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Additionally, luminaire locations can be identified by global positioning satellite (GPS) 

coordinates for easy identification, tracking and locating. With these system components in 

place, there is the potential to identify luminaire outages and schedule maintenance through the 

use of mapping software to identify and optimize maintenance routes. Using the system 

software, one can build up a database of the inventory and asset condition to improve scheduled 

maintenance.

7.4 Performance Based System Design Relating to Environmental Impacts (e.g. 

Outdoor Site-Lighting Performance - OSP)

Much work has been done in trying to establish a comprehensive method of determining the 

impact of a lighting installation for a road or site. Simply focusing on the distribution from a 

luminaire is insufficient, since this approach ignores the reflected light from the pavement or 

other direction components. The Outdoor Site-Lighting Performance method is a model 

developed by Brons et al (20) to try to quantify the total amount of light leaving a site and the 

lighting’s impact on abutters and the community. Other models have also been developed, but 

this one is included here as an example of a more holistic approach to evaluating lighting 

impacts.
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Figure 35 - Example Calculation of Lighting on Surfaces of Theoretical Box

The method essentially creates a box around a site or section of roadway and evaluates the 

amount of light on the sides and roof of the box as well as the maximum value of light on the 

vertical sides. Typical designs were investigated to get a range of values. Some provisional

criteria values were then developed for discussion.
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Figure 36 – Maximum Illuminance Level (Brons, 20)

Figure 37 – Proposed Glow Limits (Brons, 20)

7.5 Roadside Hazards

Clear zone is defined in the Roadside Design Guide 2011 as the total roadside border area, 

starting at the edge of the traveled way, available for safe use by errant vehicles. Determining the 

clear zone is a function of design speed, traffic volumes, the presence of fill and cut slopes, the 

steepness of the slopes and the horizontal curvature of the road.

Although an unobstructed roadside is highly desirable from a roadside safety viewpoint, some 

appurtenances such as light poles must be placed near the travel way. As roadway lighting is a 

road safety enhancement, poles should be placed in such a way that they do not present a hazard 

to errant motor vehicles. All new and replacement Luminaire support poles should be selected 

from those that have been successfully crash-tested. Poles should not compromise the safety of 

the road user. Details for reducing impact severity with the use of suitable breakaway pole base 

design are included in the AASHTO Roadside Design Guide (21).
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Figure 38 – Pole Spacing on Curves

Where lighting is required on roadways with small radius horizontal curvature, poles should be

positioned on the inside of the curve to reduce the potential for impacts by errant vehicles that

overrun the entry to the curve. If poles cannot be positioned on the inside of the curve, they

should be located outside of the entry overrun areas defined in Figure 38.

Poles should be offset away from the roadway at a sufficient distance to minimize potential

hazard to drivers. In urban areas with curbs and gutters, poles should be placed at the back of the

sidewalks (when possible given locations of buildings and proper sidewalk width) to reduce the 

potential contact with motor vehicles. Breakaway base should always be used unless engineering 

judgment shows that pedestrian safety could be compromised. On highways and freeways, poles 

should be placed outside the clear zone or have a suitable breakaway device if placed within the 

clear zone.
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A breakaway device typically attaches between the foundation and the pole to allow the pole to

break away upon impact by a motor vehicle. Figure 39 illustrates breakaway base characteristics

when a pole is struck by a motor vehicle. A stub height or 4 inches or less should be used to 

lessen the possibility for impacting vehicles to snag on the foundation of the breakaway support. 

Additionally the breakaway support should utilize electrical disconnects to reduce the risk of fire 

and electrical hazards after the structure is impacted by an errant vehicle.

Figure 39 – Pole with Breakaway Device
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Other Systems and Issues Related to Roadway Lighting

This section discusses roadway-related items that impact the lighting system and roadway user.
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8 Related Roadway Systems

8.1 Roadway Marking and Guidance

Retro-reflective markings, delineators, and signs can be a very cost-effective option for assisting 

a driver. When roadway lighting is not present, nighttime navigation generally depends upon on 

a road user’s visibility of the roadway and pavement markings via vehicle headlamps. These 

types of systems do not directly help in the visibility of pedestrians, cyclists, or objects on the

roadway but can greatly help in guidance and warning of known hazards.

Retro-reflective markings are designed to reflect light back to a road user’s eye and improve 

visibility. High-performance pavement markings have been developed for both wet and dry road 

conditions. 

Figure 40 - Retro-Reflective Pavement Markings

Post-mounted delineators (PMDs) are another effective method for providing delineation of 

roadway curves at night. PMDs consist of retro-reflective strips mounted on posts approximately 

1.3 m above the pavement.
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Figure 41 – Post-Mounted Delineators (PMDs)

PMDs are typically used for the benefit of marking out curves in a roadway. The Manual on

Uniform Traffic Control Devices (MUTCD, 2009) defines typical spacing for PMDs.

Retro-reflective pavement markings and post-mounted delineators can be considered as 

alternatives to lighting for rural applications where pedestrians or other unexpected hazards are 

not anticipated. 

8.2 Impact of Vehicle Headlamps

Vehicle headlamps improve a driver’s visibility of objects on the roadway. However, this is not

well quantified in the research. The effect of headlamps is not currently taken into account when 

undertaking lighting calculations and designing a roadway system. Typically, at higher speeds,

the length of the safe stopping distance exceeds the distance from the vehicle in which 

headlamps give assistance to the driver.

In order to assess the speeds where headlamps alone may be sufficient, computer modeling was 

performed (Lutkevich, 2007) using available photometric files for low-beam headlights. The 

model suggests that vehicle headlamps alone may meet the lighting requirements for low-speed 

(lower than 30 mph), low-pedestrian-activity roadways. Because this was a limited analysis, 

however, and because many variables are involved in the decision to provide supplemental 

lighting, the designer and governing authority must decide whether lighting is warranted. 

Lighting has been proven as an effective countermeasure but headlamps are a consideration

when evaluating a nighttime environment.

Figure 42 – Headlamp Modeling Example
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8.3 Temporary Roadway and Work Zone Lighting

8.3.1 Temporary Roadway Lighting

Temporary roadway lighting is typically installed where a road detour is required. It is provided 

to aid traffic flow and improve driver and pedestrian visibility during road construction and 

detours. Temporary roadway lighting levels are similar to the requirements for permanent 

roadway lighting.

Highway construction projects frequently require detours, reduced shoulder widths, reduced lane 

widths, limited pull off areas, unusual maneuvering, temporary pavement and markings, rough 

pavement, and many other conditions that make navigating the construction zone difficult. 

Temporary roadway lighting can be an effective tool for improving guidance and aiding in the 

passage of road users through a construction site.

Temporary roadway lighting is considered when one or more of the following conditions are

met:

• Where lighting exists but has to be removed for construction, and permanent lighting is not 

operational.

• The roadway does not meet geometric design standards for an extended period (more than a 

few weeks).

• Hazards are present during hours of darkness.

• Medium to high pedestrian activity occurs during hours of darkness.

• Devices such as pylons, delineators, barricades and barrels don’t provide sufficient guidance.

In the interest of economy, poles and luminaires designated for the permanent installation may 

be used for the detour and relocated to the permanent location. Highmast lighting is an efficient 

method of temporary roadway lighting since it lights areas well beyond the roadway, which may 

be used for temporary detour roads.

8.3.2 Work Zone Lighting

Work zone lighting is provided for construction activities and is not meant to serve as temporary 

roadway lighting. Work zone lighting typically involves the use of portable, high-intensity 

floodlights with portable generators to direct a high level of light onto the work area. Because 

work zone lighting is provided for worker safety, the warrant for this lighting should be 

dependent on the task at hand and the local worker safety regulations. Work zone illumination 

levels as recommended by National Cooperative Highway Research Program (NCHRP) Report 

498 are recommended.
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Figure 43 - Work Zone Lighting

Portable lighting equipment can often cause glare issues impacting a driver’s visual performance

passing through a work zone. To minimize that impact floodlights should be aimed away from 

travel lanes in a the work zone similar to the recommendation given in Figure 44. The possible 

addition of temporary roadway lighting may also be evaluated depending on locations and 

project conditions.

Figure 44 – Work Zone Floodlight Aiming
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8.4 Impact of Architectural/Aesthetic Lighting System for Roadway Facilities

Lighting can produce distinctive visual effects, and can help to shape the identity of a place. 

Poles and luminaries can be provided in custom colors and shapes to complement street furniture 

such as benches, handrails, and trash bins. Spaces designed for visual effect involving such

decorative elements are referred to as “streetscapes.”

Typically, street lighting projects involve architects who define the aesthetic elements, including 

lighting. It is important that the lighting designer work in collaboration with the architect, since 

lighting features such as pole heights, arm length, luminaire optics, and location all have an 

impact on the overall design. For example feature lighting in the center island of a roundabout 

can not only enhance the nighttime aesthetic appearance but also increase vertical luminances on 

objects possibly enhancing visibility.

Figure 45 - Streetscape Lighting

Trees and other landscape features may be included as part of a streetscape design. The lighting 

designer should consult with the architect on items such as the location of plants and trees that 

may block lighting on the roadway, or tree roots that may interfere with underground conduits or 

other electrical equipment. Coordination will also be required regarding other architectural 

elements such as benches, planters, building canopies and awnings, and other street furniture, as 

well as parking stalls and signage. Architectural requirements should never take precedence over 

safe lighting requirements.

Streetscape projects are designed to meet both the visibility requirements for drivers and the 

more subjective security and comfort considerations for pedestrians. To meet sidewalk lighting 

requirements, pedestrian-scale lighting as shown in Figure 46 is typically be required. For wider 
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roads, or in places where trees are present or proposed, taller poles with mast arms may be 

required to get lights out on the road. 

Figure 46 - Pedestrian Scale Lighting

Typical light layouts are shown in Figure 47. For two lane roads, pedestrian-scale lighting may 

provide the required level of illumination for the street and sidewalk. However, if this does not 

produce the required results or if the roads are wider (4 or more lanes), pedestrian-scale lighting 

will typically have to be supplemented with taller overhead lighting poles. The main purpose of 

the overhead lighting is get the luminaries on mast arms extended over the road beyond to tree 

canopies to light the street. The pedestrian-scale lighting will provide illumination for the 

sidewalk. 
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Figure 47 - Streetscape Lighting Layouts

Visibility on the sidewalk and streets can also be reduced if trees block the light and create 

shadows that reduce uniformity and visibility (Figure 48). A study titled Trees, Lighting and 

Safety in Context Sensitive Design (24) gave some examples of how a lighting system should be 

designed to allow for the presence of trees at all stages of maturity:

• The best design approach is to locate luminaires outside of the full growth lines of the species 

of tree along the roadway.

• When a roadway or pedestrian lighting project includes new or existing trees in close 

proximity to the lighting, an additional light loss factor should be included in the design to 

accommodate light loss due to shading. Insufficient research is available at this time to 

quantify the factor with precision, but an additional 10 - 20 percent is reasonable. 
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Figure 48 - Trees Blocking Light

Figure 49 - Comparison of sidewalk areas in winter (without leaves) and summer (with leaves)
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9 Summary

There are significant resources available for application and considerations relating to street and 

roadway lighting. These resources are constantly changing as research and practice evolve in the

field of outdoor lighting. Much is left to learn about optimizing visibility for the roadway user 

while balancing the impacts and best cost/benefit of available safety improvements.

This handbook, with the research and documents referenced within it, provides a solid base for 

policy makers, owners, designers, and installers in the decision making process. Much is 

changing in this field. Research is ongoing in the areas of mesopic vision, adaptive lighting, 

spectral impacts to visibility/contrast, and better predictive models. New lighting sources

continue to develop and emerge which are changing the way roadway lighting design is 

approached and designed. The user of this handbook is encouraged to remain current on the 

resources provided by FHWA, AASHTO, IES, CIE, and other technical organizations.
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References

1. FHWA, European Road Lighting Technologies, Report No. FHWA-PL-01-034, 

Washington, DC, 2001

2. FHWA, 1996 Annual Report on Highway Safety improvement Programs. Report No. 

FHWA-SA-96-040. Washington, DC: USDOT, FHWA, 1996

3. FHWA, Signalized Intersections: Informational Guide. Report No. FHWA-HRT-04-091 

Washington, DC, 2004

4. ELVIK, R. and T. VAA, Handbook of Road Safety Measures, Oxford, United Kingdom, 

2004

5. WANVIK, Road Lighting and Traffic Safety, Norwegian University of Science and 

Technology, 2009

6. LIPINSKI, M.E. and R.H. WORTMAN. “Effect of Illumination on Rural At-Grade 

Intersection Crashes.” Report 611. Transportation Research Record, 1976. pp 25–27.

7. ROBERTS, S.E. and F.W. WALKER. “Influence of Lighting on Accident Frequency at 

Highway Intersections.” Report 562. Transportation Research Record, 1976, pp 73-77.

8. ISEBRANDS, H. et al, Safety Impacts of Street Lighting at Isolated Rural Intersections, 

Minnesota Department of Transportation, Part II, MN/RC-2006-35, September 2006

9. FHWA, Highway Design Handbook for Older Drivers and Pedestrians, Report No. 

FHWA-RD-01-103, Washington, DC, 2001

10. FHWA, Railroad-Highway Grade Crossing Handbook, Report No. FHWA-SA-07-010, 

Washington, DC, 2007

11. FHWA, Informational Report on Lighting Design for Midblock Crosswalks, Publication 

Number: FHWA-HRT-08-053, April 2008 

12. ADRIAN, W. Visibility of Targets: Model for Calculation. Lighting Research and 

Technology, 21(4), 180-188, 1989

13. BLACKWELL, H. 1946. Contrast threshold of the human eye. Journal of the Optical 

Society of America, 36(11), 624-643.
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14. AASHTO, A Policy on Geometric Design of Highways and Streets, 6th Ed., second 

printing, American Association of State Highway and Transportation Officials, 

Washington, DC, 2011

15. REA, M. et al, A Proposed Unified System of Photometry, Lighting Research and 

Technology, Vol. 36 No. 2 85-109, June 2004

16. Preston, H. and T. Schoenecker. Safety Impacts of Street Lighting at Isolated Rural 

Intersections. Final Report MN/RC-1999-17. Minnesota Department of Transportation, April 

1999.

17. BARTCH, C. et al, Evidence for Modulation of Melatonin Secretion in Men with Benign 

and Malignant Tumors of the Prostate: Relationship with the Pituitary Hormones, J. 

Pineal Res. 2:121-132, 1985

18. FIGUEIRO, M., REA, M., and BULLOUGH, J. Does Architectural Lighting Contribute 

to Breast Cancer, Journal of Carcinogenesis, 5:20, August 2006

19. FHWA, Guidelines and Recommendations to Accommodate Older Driver and 

Pedestrians, FHWA-RD-01-051, Washington, DC. 2001

20. BRONS, JA et al, Outdoor site-lighting performance: A comprehensive and quantitative 

framework for assessing light pollution, Lighting Res. Technol, 40: 201-224, 2008

21. AASHTO, Roadside Design Guide, American Association of State Highway and 

Transportation Officials, Washington, DC, 4th Edition, 2011

22. GREEN, M. Methodological Analysis of Driver Perception-Brake Times" Transportation 

Human Factors, 2, pp 195-216, 2000

23. GREEN, M, et al Forensic Vision with Application to Highway Safety, 3rd edition, June 

2008

24. HASSON, P, et al, Trees, Lighting, and Safety in Context-Sensitive Solutions, 

Transportation Research Board, Issue 2120, pp 101-111, 2009

25. AASHTO, Highway Safety Manual, American Association of State Highway and 

Transportation Officials, Washington, DC, 2010

26. AASHTO, Roadway Lighting Design Guide, American Association of State Highway 

and Transportation Officials, Washington, DC, 2005

27. TAC, Guide for the Design of Roadway Lighting, Transportation Association of Canada

Volume 1 – Fundamentals and Volume 2 – Design January 2006
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28. ANSI/IES, American National Standard Practice for Roadway Lighting, Illuminating 

Engineering Society, RP-8-00 (reaffirmed in 2005)

29. ANSI/IES American National Standard Practice for Roadway and Street Lighting, 

Illuminating Engineering Society, RP-8-10 (document in draft form, not yet approved by 

the IES)

30. NCHRP, Warrants for Highway Lighting, National Cooperative Highway Research 

Program Report 152, 1974

31. NCHRP Roundabouts: An Informational Guide – Second Edition, Report No. 672, 

Washington, DC, 2000
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 Glossary of Terms
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Accommodation: the process by which the eye changes focus from one distance to another.

Adaptation: the process by which the visual system becomes accustomed to more or less light

or of a different color than it was exposed to during an immediately preceding period. It results

in a change in the sensitivity of the eye to light.

Arrangement: the repeating pattern of luminaires on a roadway. Usually described as opposite,

staggered, one-side, center-suspended, or median mounted.

Ballast: a device used with an electric-discharge lamp to obtain the necessary circuit

conditions (voltage, current and waveform) for starting and operating.

Beacon lighting: a single luminaire that will identify the presence of an intersection or an 

interchange or potential conflict with other traffic and physical features and will serve as a 

warning or marker. 

Bifurcation area: the triangular shaped area between two diverging lanes, beyond the point of 

physical separation of one lane from the other. This area is immediately beyond the decision 

point where a driver must commit to one lane or the other, and lies in the direct line of travel of 

an overrunning vehicle.

bidirectional reflectance-distribution function (BRDF): the ratio of the differential 

luminance of a ray reflected in a given direction to the differential luminous flux density

incident from a given direction of incidence, which produces it.

Bikeway: any road, street, path, or way that in some manner is specifically designated as

being open to bicycle travel, regardless of whether such facilities are designated for the exclusive

use of bicycles or are to be shared with other transportation modes.

Brightness: see luminance and subjective brightness.

Candela, cd: the SI unit of luminous intensity. One candela is one lumen per steradian.

Formerly candle.

(See Figure 50.)

Candela per square meter, Cd/m2 :the SI unit of luminance equal to the uniform luminance

of a perfectly diffusing surface emitting or reflecting light at the rate of one lumen per square

meter or the average luminance of any surface emitting or reflecting light at that rate.

Candlepower, cp: luminous intensity expressed in candelas. (It is no indication of the total

lumen output)

Central (foveal) vision: the seeing of objects in the central or foveal part of the visual field,

approximately two degrees in diameter. It permits seeing much finer detail than does peripheral

vision.
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Contrast sensitivity: the ability to detect the presence of luminance differences. 

Quantitatively, it is equal to the reciprocal of the contrast threshold.

contrast see luminance contrast.

Contrast threshold: the minimal perceptible contrast for a given state of adaptation of the

eye. It also is defined as the luminance contrast detectable during some specific fraction of the

times it is presented to an observer, usually 50 percent.

Conflict: A conflict occurs whenever the paths followed by vehicles diverge, merge or cross

Conflict Area: Is an area of a roadway where the motorist’s special attention is required in 

order to interpret the functional features (e.g. bullnose) and / or activities (e.g. pedestrians, 

turning vehicles, railroad grade crossing) of the roadway, in order to make a decision on their 

driving routine. It is that area which encompasses all of the conflict points.

Conflict Points: Points at which conflicts can occur.

Continuous Lighting: A fixed overhead lighting system designed to provide a specific level of 

illuminance, luminance and uniformity of light on the roadway throughout a highway complex. 

Crosswalk: see pedestrian crosswalk.

Diffuse reflectance: the ratio of the flux leaving a surface or medium by diffuse reflection to the

incident flux.

Directional reflectance: the reflectance in a given direction from an incident ray reaching the

surface or medium from a given direction. See bidirectional reflectance-distribution

function.

Disability glare: glare resulting in reduced visual performance and visibility. It often is

accompanied by discomfort. See veiling luminance.

Discomfort glare: glare producing discomfort. It does not necessarily interfere with visual

performance or visibility.

Entrance Ramp Conflict Area: That area of an entrance ramp from the bullnose (covering 

both the ramp lane(s) and the right through lane) to the end of the ramp taper.

Exit Ramp Conflict Area: That area of an exit ramp and the right through lane from the 

beginning point of the bifurcation area (neutral area) to the end of the gore area and extended 15 

to 40 meters- dependant on the design speed- for both the ramp lane(s) and the right through 

lane.
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Footcandle, fc: the unit of illuminance when the foot is taken as the unit of length. It is the

illuminance on a surface one square foot in area on which there is a uniformly distributed flux

of one lumen, or the illuminance produced on a surface all points of which are at a distance of

one foot from a directionally uniform point source of one candela.

Glare: the sensation produced by luminance within the visual field that is sufficiently greater

than the luminance to which the eyes are adapted to cause annoyance, discomfort, or loss in

visual performance and visibility. See disability glare, discomfort glare.

Intersection: the general area where two or more roadways (highways) join or cross, including the

roadway and roadside facilitiesfor traffic movement within it.

Intersection Conflict Area: That area of an intersection that is extended to cover the conflict 

area

Lambertian surface: a surface that emits or reflects light in accordance with Lambert’s

cosine law. A Lambertian surface has the same luminance regardless of viewing angle.

Lamp: a generic term for an artificial source of light. 

Lamp life: the average life of a lamp defined as the total operating hours at which 50 percent

of any group of lamps is still operating.

Figure 2 - Relationship between candelas, lumens, lux, and

footcandles:

A uniform point source (luminous intensity or 

candlepower = one candela) is shown at the 

center of a sphere of unit radius whose surface 

has a reflectance of zero. The illuminance at any 

point on the sphere is one lux (one lumen per 

square meter) when the radius is one meter, or 

one footcandle (one lumen per square foot) when 

the radius is one foot. The solid angle subtended 

by the area A,B,C,D is one steradian. The flux 

density is therefore one lumen per steradian, 

which corresponds to a luminous intensity of one 

candela as originally assumed. The sphere has a 

total area of 4 (or 12.57) square units (square meters or square feet), and there is a luminous

flux of one lumen falling on each unit area. Thus the source provides a total of 12.57 lumens.
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High mast lighting: illumination of a large area by means of a group of luminaires which are

designed to be mounted in fixed orientation at the top of a high support or pole (generally 20

meters or higher).

Illuminance, E: the density of the luminous flux incident on a surface; it isthe quotient of the

luminous flux by the area of the surface when the latter is uniformly illuminated.

Illuminance (lux or footcandle) meter: an instrument for measuring illuminance on a 

plane. Instruments which accurately respond to more than one spectral distribution (color) are

color corrected. Instruments which accurately respond to more than one spatial distribution of

incident flux are cosine corrected. The instrument is comprised of some form of photo-detector

with or without a filter, driving a digital or analog readout through appropriate circuitry.

Intensity: a shortening of the terms luminous intensity and radiant intensity.

Lamp lumen depreciation factor, LLD: the multiplier to be used in calculations to relate the

initial rated output of light sources to the anticipated minimum output based on the relamping

program to be used.

Lamp post: a support or pole provided with the necessary internal attachments for wiring and

the external attachments for the bracket and/or luminaire.

Light loss factor, LLF: a factor used in a lighting calculation after a given period of time and

under given conditions. It takes into account temperature and voltage variations, dirt

accumulation on luminaire surfaces, lamp lumen depreciation, maintenance procedures,

equipment and ballast variations. Formerly called maintenance factor.

Line of sight: the line connecting the point of observation and the point of fixation.

Lumen, lm: the SI unit of luminous flux. Radiometrically, it is determined from the

radiant power. Photometrically, it is the luminous flux emitted within a unit solid angle (one

steradian) by a point source having a uniform luminous intensity of one candela.

Luminaire: a complete lighting unit consisting of a lamp or lamps together with the parts

designed to distribute the light, to position and protect the lamps and to connect the lamps to the

power supply. Sometimes includes ballasts and photocells.

Luminaire cycle: the distance between two luminaires along one side of the roadway. Note: this

may not be the same as luminaire spacing along the centerline considering both sides of the

road. (See spacing.)

Luminaire dirt depreciation factor, LDD: the multiplier to be used in lighting calculations

to reduce the initial light level provided by clean, new luminaires to the light level that they will
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88

provide due to dirt collection on the luminaires at the time at which it is anticipated that

cleaning procedures will be instituted.

Luminance, L (cd/m2): the quotient of the luminous flux at an element of the surface

surrounding the point, and propagated in directions defined by an elementary cone containing

the given direction, by the product of the solid angle of the cone and area of the orthogonal

projection of the element of the surface on a plane perpendicular to the given direction.The

luminous flux may be leaving, passing through, and/or arriving at the surface. Note: In

common usage the term “brightness” usually refers to the strength of sensation which results

from viewing surfaces or spaces from which light comes to the eye. This sensation is 

determined in part by the definitely measurable luminance defined above and in part by

conditions of observation such as the state of adaptation of the eye.

Luminance contrast: the relationship between the luminances of an object and its

immediate background.

Luminance meter: an instrument for measuring the luminance of an object or surface.

Instruments which accurately respond to more than one spectral distribution (color) are color

corrected. The instrument is comprised of some form of a lens system and aperture creating an

image on a photodetector, driving a digital or analog readout through appropriate circuitry.

Luminous efficacy of a source of light: the quotient of the total luminous flux emitted by the

total lamp power input. It is expressed in lumens per watt.

Luminous flux density at a surface: the luminous flux per unit area at a point on a surface.

Note: this need not be a physical surface; it may equally well be a mathematical plane.

Luminous intensity, I (cd): the luminous flux per unit solid angle in a specific direction. Hence,

it is the luminous flux on a small surface normal to that direction, divided by the solid angle (in

steradians) that the surface subtends at the source.

Lux, lx: the SI unit of illuminance. It is the illuminance on a surface one square meter in area on

which there is a uniformly distributed flux of one lumen, or the illuminance produced at a surface

all points of which are at a distance of one meter from a uniform point source of one candela.

Mean lamp lumens: the mean lumen output of a lamp is calculated by determining the

area beneath the lumen maintenance characteristic curve of that source over a given period of

time and dividing that area by the time period in hours.

Mounting height, MH: the vertical distance between the roadway surface and the center of the

apparent light source of the luminaire.

Overhang,OH: the horizontal distance between a vertical line passing through the luminaire

light center and the curb or edge of the travelled roadway.
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Partial Lighting: Partial Lighting refers to lighting installed at the decision areas of isolated 

interchanges and intersections whereby it provides visibility of potential conflicts with other 

traffic and physical features.

Pedestrian crosswalk: an area designated by markings for pedestrians to cross the roadway.

Pedestrian way: a sidewalk or pedestrian walkway, usually paved, intended for pedestrian

usage.

Point of fixation: a point or object in the visual field at which the eyes look and upon

which they are focused.

R-table: a table for a particular pavement type which provides reduced luminance coefficients

in terms of the variable angles, beta and tan gamma.

Reaction time: the interval between the beginning of a stimulus and the beginning of the

response of an observer.

Setback: the lateral offset of the pole center from the face of the curb or edge of the travelled

way.

Spacing: the distance between successive luminaires measured along the center line of the

street. See luminaire cycle.

Spacing-to-mounting height ratio, S/MH: the ratio of the distance between luminaire

centers, along the center line of the street, to the mounting height above the roadway.

Subjective brightness: the subjective attribute of any light sensation given rise to the

perception of luminous intensity, including the whole scale of qualities of being bright, lightness,

brilliant, dim, or dark.

Traffic conflict area: area on a road system where a strong potential exists for collisions

between vehicles or between vehicles and pedestrians.

Veiling luminance: a luminance superimposed on the retinal image which reduces its

contrast. It is this veiling effect produced by bright sources or areas in the visual field that

results in decreased visual performance and visibility.

Visibility: the quality or state of being perceivable by the eye. In many outdoor applications,

visibility is sometimes defined in terms of the distance at which an object can be just

perceived by the eye. In indoor and out- door applications it usually is defined in terms of the

contrast or size of a standard test object, observed under standardized view-conditions, having 

the same threshold as the given object.
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Visibility index, VI: a measure closely related to visibility level sometimes used in connection

with road lighting applications.

Visibility level,VL: a contrast multiplier to be applied to the visibility reference function or

provide the luminance contrast required at different levels of task background luminance to

achieve visibility for specified conditions relating to the task and observer.

Visual angle: the angle subtended by an object or detail at the point of observation. It

usually is measured in minutes of arc.

Walkway: a sidewalk or pedestrian way.