Download Glare and Night Time Driving

GLARE & NIGHT TIME
DRIVING
GLARE…
 Harsh uncomfortably bright light.
 It’s a sensation in response to light that can
take a number of forms.
 Results from bright, steady, dazzling light or
from shiny surfaces.
 Can also caused by very bright foreground.
GLARE…
 Or by light reflected by fog or snow.
 Glare affects both day & night driving
performance.
 Effects of glare on drivers are classified
-Discomfort glare
-Disability glare
Disability Glare
 Also known as physiological glare.
 Created by bright light.
 Its comes from light scattering in the occular
media.
 Reduce driver’s ability to perform visual task.
 Glaring light scattered in the eye can be
expressed as superposition of uniform
luminance onto retinal image.
Discomfort Glare
 Bright light
 Cause discomfort or annoyance
 Scale of discomfort glare was used by DeBoer.
 Influenced by 3 factors
-location of glare source
-luminance of background
-luminance & size of glare source
HEADLAMP GLARE
 Vehicle headlamps illuminate the area ahead of
vehicle and overhead signs.
 Essential part of roadway visibility system.
 Must provide sufficient lighting in the field of
view of a driver.
 Headlamps need to produce and project high
light levels.
Causes of Headlight Glare
 Illumination from the glare source
 Glare angle
 Back ground luminance
 Size of the glare source
 Glare source luminance
 Driver age
 Reflective surfaces
 Glare from mirrors
GLARE ON TWO LANE
HIGHWAYS..
 Lower Light levels
 Oncoming traffic closer to driver’s line of sight
 Complex Roadway geometry
 Less restricted roadway access
 Less roadway markings
 Closer proximity of pedestrians
Lower Light Levels
 Visibility of an object depends on overall
light levels
 Pole mounted roadway lighting help to see
on unlighted roads
 Visibility depends on the contrast of an
object against its background
 Glare reduce visibility
Oncoming traffic closer to
driver’s line of sight
Complex Roadway
Geometry
LESS RESTRICTED
ROADWAY
ACCESS
 Discomfort from headlamp glare increases
when visual task is more difficult
 Chances for hazard along a two lane highway
is greater
 Vehicles enter from variety of locations and
directions
 Not restricted for bicycle travel or pedestrian
use
Fewer roadway markings
 Multi-lane highways are marked with
indications for traffic lanes
 Two-lane highways may not have median lines
or nor markings
 Roadway markings facilitate efficient & safe
driving
 No direct impact on driver
 Provide visual guidance to a driver
CLOSER PROXIMITY OF
PEDESTRIANS
 On two lane highways pedestrians more closer to
vehicle traffic
 Less common on highways but are not restricted
 Pedestrians themselves are not always easily seen
 Dark cloths have less reflectance
 Do not provide much contrast against the roadway
pavement
 Pedestrians themselves often overestimate how visible
they are to oncoming traffic
COUNTERMEASURES TO
CONTROL GLARE
-By reducing the illumination
-By increasing glare angle
-Indirect measures
To reduce illumination
reaching
driver’s
eye
GLARE SCREENS
• Placed in the median of roadway
• Cost effective way to reduce glare
• Improve safety in temporary work zone
• Any type of object with certain width and
placed at certain spacings that prevent glare
• Three types-type1,type2,type3
• Type1-continous and block light from all
angles
• Eg: earth mounds and concrete barriers
• Type2-continous screen of an open material
opaque to light coming from angle of 0-20
degrees
• Transparent for beyond 20 degrees
 Eg: expanded metal mesh, knit polyester fabric
and fencing
 Type3- made up of individual elements that
block light from angles of zero to 20 degrees
 Provide clear visibility beyond 20 degrees
 Manufactured by individually supported
paddles at intervals
ROADSIDE PLANTATION
• Glare can be controlled by planting trees or
bushes in the median
• Position of trees should be fixed
• Should be sufficiently away from carriage way
• Tree guard should be prepared to protect the
young sapling
 Prevent glare from sunlight as well as from
vehicle headlamps
POLARIZED LIGHTING
 Ordinary light consists of electromagnetic
waves which vibrate in all directions
 When passes through polarizing filter light
waves are absorbed
 Become linearly polarized
 Can improve visibility by decreasing the
amount of light from oncoming headlights.
 Both vehicles should be equipped with the
proper hardware
 Should have a polarizer and analyser or
polarizing filter
NIGHT DRIVING GLASSES
 Used for glare reduction
 Similar to sunglasses
 They filter light prior to reaching driver’s eye
 Improve night time vision and night driving
safety
To increase the glare angle
INCREASE MEDIAN WIDTH
 AASHTO refers median as a portion of
divided highway separating the travelled
way for traffic in opposing directions
 Provide recovery area for out-of-control
vehicles
 Provide stopping area
 May be depressed or raised
 Increasing median width decreases the effects
of glare from opposing headlights
 Increasing lateral separation shifts the beam
pattern of the opposing vehicle and results in
lower intensities of light
 Reduce both disability and glare
INDEPENDENT ALIGNMENT
 Those with horizontal and vertical alignment
 Places each roadway at a different elevation
 Used where there is large median width
 Eliminates glare entirely
Indirect measures to
reduce
effects
of
glare
ULTRAVIOLET HEADLIGHTS
 Reduce glare on highways by reducing the need of
visible light
 Improve night time visibility of pedestrians, lane lines,
signs and other objects
 UV radiations when absorbed get converted to longer
wave length visible light-FLUORESCENCE
 It makes objects more easily seen
 Improve highway safety
FIXED ROADWAY LIGHTING
 Designed according to 3 methods
-illuminance
-pavement luminance
-visibility
 Reduce night time accidents
 Improve pedestrians safety
 Mitigate the effect of glare
CONCLUSION
 Not possible to recommend one counter measure that
would eliminate discomfort glare for everyone in all
situations.
 Glare at night can be mitigated by design changes in
roadway, automobiles, and vehicles lighting systems
and thus improve night vision on highways.
 No of counter measures can be implemented with
minimal cost for glare reduction
REFERENCES
 Avijit Ghosh, Bagui S.K., & Jha S.K. (2004) “highway
design considering glare”, Indian highways, vol.33,
no.12.pp. December 2004.
 Ambarish Ghosh & Swapan Kumar “visual systems
and glare”, Indian highways, August 2009.
 Adrain W, “A method for Design of Tunnel Entrance
Lighting”, Journal Roads and Streets, pp.125-133.
 Duncan,D.D. (1996), “Nighttime glare Reduction and
Illumination Enhancement ”, Report No. FS-96-037,
Johns Hopkins Applied Physics Laboratory, Fleet systems
THANK YOU...