© 2015 Rensselaer Polytechnic Institute. All rights reserved. Luminous Intensity Requirements for Service Vehicle Warning Beacons (TRB Paper 15-1117) John

© 2015 Rensselaer Polytechnic Institute. All rights reserved.

Luminous Intensity Requirements for Luminous Intensity Requirements for Service Vehicle Warning BeaconsService Vehicle Warning Beacons

(TRB Paper 15-1117)(TRB Paper 15-1117)

John D. Bullough, Mark S. ReaJohn D. Bullough, Mark S. ReaLighting Research Center, Rensselaer Polytechnic InstituteLighting Research Center, Rensselaer Polytechnic Institute

Transportation Research Board Annual MeetingTransportation Research Board Annual MeetingJanuary 11-15, 2015January 11-15, 2015


Relevance of Warning Beacon Design Relevance of Warning Beacon Design to Safetyto Safety There are about 316,000 warning There are about 316,000 warning

beacons in the U.S. (Cook et al. beacons in the U.S. (Cook et al. 2000; US Census 2009)2000; US Census 2009)

Workers in transportation, Workers in transportation, construction and utilities are over-construction and utilities are over-represented in work-related represented in work-related fatalities (NIOSH 2014)fatalities (NIOSH 2014)

Improved beacon design could help Improved beacon design could help prevent 70 fatalities and 5200 prevent 70 fatalities and 5200 injuries annually in the U.S. (Cook injuries annually in the U.S. (Cook et al. 2000)et al. 2000)

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Warning Beacon Performance Warning Beacon Performance StandardsStandards

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Vehicle-mounted warning beacon performance Vehicle-mounted warning beacon performance is specified by several standards from the is specified by several standards from the Society of Automotive Engineers (SAE)Society of Automotive Engineers (SAE)› SAE J595: Flashing Warning Lamps for Authorized SAE J595: Flashing Warning Lamps for Authorized

Emergency, Maintenance and Service VehiclesEmergency, Maintenance and Service Vehicles• Yellow: 1-2 flashes/second, peak intensity (when on) Yellow: 1-2 flashes/second, peak intensity (when on)

of 600 candelasof 600 candelas

› SAE J845: Optical Warning Devices for Authorized SAE J845: Optical Warning Devices for Authorized Emergency, Maintenance and Service VehiclesEmergency, Maintenance and Service Vehicles

• Yellow: 1-2 flashes/second, peak flash energy of 90 Yellow: 1-2 flashes/second, peak flash energy of 90 candela·seconds (emergencies), 22 candela·seconds candela·seconds (emergencies), 22 candela·seconds (warning), 10 candela·seconds (identification)(warning), 10 candela·seconds (identification)

What is a candela·second?What is a candela·second?


Warning Beacon Performance Warning Beacon Performance Standards (cont’d.)Standards (cont’d.)

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Warning beacon performance is specified by several standards Warning beacon performance is specified by several standards from the Society of Automotive Engineers (SAE)from the Society of Automotive Engineers (SAE)› SAE J1318: Gaseous Discharge Warning Lamp for Authorized Emergency, SAE J1318: Gaseous Discharge Warning Lamp for Authorized Emergency,

Maintenance and Service VehiclesMaintenance and Service Vehicles• Yellow: 1-4 flashes/second, flash energy of 90-100 candela·seconds Yellow: 1-4 flashes/second, flash energy of 90-100 candela·seconds

(emergencies), 22 candela·seconds (warning), 10 candela·seconds (emergencies), 22 candela·seconds (warning), 10 candela·seconds (identification)(identification)


Suitability of Existing StandardsSuitability of Existing Standards

The 600-cd luminous intensity value from SAE The 600-cd luminous intensity value from SAE J595 is consistent with data from Howard and J595 is consistent with data from Howard and Finch (1960)Finch (1960)

Intensity requirements do not take ambient Intensity requirements do not take ambient conditions (e.g., daytime versus nighttime) into conditions (e.g., daytime versus nighttime) into accountaccount› Presumably they are minima for daytime viewingPresumably they are minima for daytime viewing› No maximum requirements for glare controlNo maximum requirements for glare control

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Experimental MethodExperimental Method

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Three laboratory experiments were conducted to measure response Three laboratory experiments were conducted to measure response times to flashing warning beacons, and impacts on hazard visibilitytimes to flashing warning beacons, and impacts on hazard visibility

Participants viewed a low-contrast target adjacent to or 5Participants viewed a low-contrast target adjacent to or 5oo from a from a simulated truck with a warning beacon (LED: peak wavelength 590 nm, simulated truck with a warning beacon (LED: peak wavelength 590 nm, half-bandwidth 18 nm) with adjustable peak luminous intensity (80-half-bandwidth 18 nm) with adjustable peak luminous intensity (80-3100 cd)3100 cd)


Experimental ConditionsExperimental Conditions

Experiment 1: Simple scenes (day/night, on/off-Experiment 1: Simple scenes (day/night, on/off-axis location)axis location)

Experiment 2: Simple scenes with visual clutter Experiment 2: Simple scenes with visual clutter (day/night, on/off-axis location)(day/night, on/off-axis location)

Experiment 3: Realistic scenes (day/night, on/off-Experiment 3: Realistic scenes (day/night, on/off-axis, with/without visual clutter)axis, with/without visual clutter)

Total n=17 (5F/12M), aged 31-67 years (mean Total n=17 (5F/12M), aged 31-67 years (mean 49), with current driver’s licenses49), with current driver’s licenses

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© 2015 Rensselaer Polytechnic Institute. All rights reserved.8

Simple Daytime Background Scene: Experiment 1Simple Daytime Background Scene: Experiment 1


Simple Nighttime Background Scene: Experiment 1


Experiment 1 (No Clutter): Experiment 1 (No Clutter): Response TimesResponse Times

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Response times to warning beacons viewed on-Response times to warning beacons viewed on-axis reached asymptotic (minimum) values for axis reached asymptotic (minimum) values for both daytime and nighttime conditions for the both daytime and nighttime conditions for the

range of peak luminous intensities investigated.range of peak luminous intensities investigated.

Response times to warning beacons viewed off-Response times to warning beacons viewed off-axis were asymptotic for nighttime conditions axis were asymptotic for nighttime conditions but not for daytime conditions. The interaction but not for daytime conditions. The interaction between ambient condition and peak luminous between ambient condition and peak luminous

intensity on response times is evident.intensity on response times is evident.


Experiment 1 (No Clutter): Experiment 1 (No Clutter): Target Visibility RatingsTarget Visibility Ratings

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Ratings of fixation target visibility decreased Ratings of fixation target visibility decreased slightly with higher on-axis warning beacon slightly with higher on-axis warning beacon peak intensities for the nighttime conditions.peak intensities for the nighttime conditions.

Ratings of fixation target visibility were largely Ratings of fixation target visibility were largely unaffected by off-axis warning beacons for all unaffected by off-axis warning beacons for all

peak intensities.peak intensities.


Simple Nighttime Background Scene with Visual Clutter: Experiment 2


Experiment 2 (Visual Clutter): Experiment 2 (Visual Clutter): Response TimesResponse Times

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Response times to warning beacons viewed on-Response times to warning beacons viewed on-axis reached asymptotic values for nighttime, axis reached asymptotic values for nighttime, but not daytime conditions for the range of but not daytime conditions for the range of

peak luminous intensities.peak luminous intensities.

Response times to warning beacons viewed off-Response times to warning beacons viewed off-axis reached asymptotic values at higher peak axis reached asymptotic values at higher peak

intensities for daytime than for nighttime intensities for daytime than for nighttime conditions.conditions.


Experiment 2 (Visual Clutter): Experiment 2 (Visual Clutter): Target Visibility RatingsTarget Visibility Ratings

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Ratings of fixation target visibility decreased Ratings of fixation target visibility decreased slightly at the highest on-axis warning beacon slightly at the highest on-axis warning beacon

peak intensity for nighttime conditions.peak intensity for nighttime conditions.

Ratings of fixation target visibility were slightly Ratings of fixation target visibility were slightly lower under nighttime than daytime conditions lower under nighttime than daytime conditions at the highest off-axis warning beacons peak at the highest off-axis warning beacons peak

intensity.intensity.


Realistic Daytime Background Scene, No Visual Clutter: Experiment 3Realistic Daytime Background Scene, No Visual Clutter: Experiment 3

CAUTION

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Realistic Nighttime Background Scene, with Visual Clutter: Experiment 3


Experiment 3 (Realistic Scenes): Experiment 3 (Realistic Scenes): Response TimesResponse Times

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Response times to warning beacons viewed Response times to warning beacons viewed on-axis reached asymptotic values for the on-axis reached asymptotic values for the

range of peak luminous intensities under both range of peak luminous intensities under both daytime and nighttime conditions.daytime and nighttime conditions.

Response times to warning beacons viewed Response times to warning beacons viewed off-axis differed with and without clutter and off-axis differed with and without clutter and

between daytime and nighttime for the between daytime and nighttime for the lowest peak intensity.lowest peak intensity.


Experiment 3 (Realistic Scenes): Experiment 3 (Realistic Scenes): Target Visibility RatingsTarget Visibility Ratings

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Ratings of fixation target visibility decreased Ratings of fixation target visibility decreased very slightly at the highest on-axis warning very slightly at the highest on-axis warning

beacon peak intensity for nighttime conditions.beacon peak intensity for nighttime conditions.

Ratings of fixation target visibility were largely Ratings of fixation target visibility were largely unaffected by the off-axis warning beacon unaffected by the off-axis warning beacon

peak intensity.peak intensity.


DiscussionDiscussion

Luminous intensity specifications differing for daytime Luminous intensity specifications differing for daytime and nighttime are justifiedand nighttime are justified

SAE J595 luminous intensity requirements are SAE J595 luminous intensity requirements are reasonable for daytime viewing conditions but excessive reasonable for daytime viewing conditions but excessive for nighttimefor nighttime

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Next StepsNext Steps

Outdoor field trials will be conducted to validate Outdoor field trials will be conducted to validate laboratory study findingslaboratory study findings

Coordination of multiple warning beacons on Coordination of multiple warning beacons on one or more vehicles will also be investigatedone or more vehicles will also be investigated

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A Roadway Incident Scene TodayA Roadway Incident Scene Today

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Photo: http://bangordailynews.com/2013/03/19/news/bangor/route-9-closed-for-accident-bangor-hydro-truck-also-hit-dispatcher-says/Photo: http://bangordailynews.com/2013/03/19/news/bangor/route-9-closed-for-accident-bangor-hydro-truck-also-hit-dispatcher-says/


A Roadway Incident Scene Tomorrow?A Roadway Incident Scene Tomorrow?

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Photo: http://bangordailynews.com/2013/03/19/news/bangor/route-9-closed-for-accident-bangor-hydro-truck-also-hit-dispatcher-says/Photo: http://bangordailynews.com/2013/03/19/news/bangor/route-9-closed-for-accident-bangor-hydro-truck-also-hit-dispatcher-says/


AcknowledgmentsAcknowledgments

Sponsor: National Institute of Occupational Safety and Sponsor: National Institute of Occupational Safety and Health (NIOSH Grant R01OH01065-01A1 to M. Rea)Health (NIOSH Grant R01OH01065-01A1 to M. Rea)

Nicholas Skinner and Dennis Guyon, Lighting Research Nicholas Skinner and Dennis Guyon, Lighting Research CenterCenter

Philip Garvey, Eric Donnell and Martin Pietrucha, Philip Garvey, Eric Donnell and Martin Pietrucha, Pennsylvania State UniversityPennsylvania State University

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© 2015 Rensselaer Polytechnic Institute. All rights reserved. Luminous Intensity Requirements for Service Vehicle Warning Beacons (TRB Paper 15-1117) John