A status of energy efficient LED traffic
signals in Korea
Bong-Man Jung
71-2, Jang-dong, Yusung-ku, Taejon, Rep. of Korea, 305-343, Electrics & Lighting Research Center, Korea Institute of Energy
Research, Email: bmjung@kier.re.kr
Hak-Geun Jeong
71-2, Jang-dong, Yusung-ku, Taejon, Rep. of Korea, 305-343, Electrics & Lighting Research Center, Korea Institute of Energy
Research, Email: hgjeong@kier.re.kr
Soo-Bin Han
71-2, Jang-dong, Yusung-ku, Taejon, Rep. of Korea, 305-343, Electrics & Lighting Research Center, Korea Institute of Energy
Research, Email: sbhan@kier.re.kr
K EY WO R D S
LED traffic signal, Korean-type LED traffic signal specifications
A B S T RA C T
Concerning Korean energy consumption, 20% of the total electrical energy (96% is now exported) is consumed in
lighting area. Accordingly, it is one of the most important
governmental policies to efficiently utilize electricity due
to development and application of high-efficiency lighting
equipment. In Korea, widely-built traffic signals employ an
incandescent and are of 100W/300 mm, and 280,080set/
801,932lamps have been installed and operated by 1999.
Of them, 58% (161,181set), 25% (69,655set) and 18%
(49,244set) correspond to traffic signals, pedestrian signals
and other supplementary signals respectively. It was estimated that electrical energy consumed 28MW instantaneously, 245GWH annually and 20million EU, 40million EU
are expended as annual electricity fee and maintenance fee
respectively. On the other hand, the LED traffic signal is
expected to be a future traffic signal since if traffic signals
are replaced by LEDs, energy saving effect of 85% and drop
of 75% in maintenance fee will be obtained. In this paper,
development procedure, main features of proposed Korean-type LED traffic signal specifications, on road test results and economical effects are introduced.
INTRODUCTION
The spread of LED traffic signal is now impossible in Korea, though it has such advantages as large energy saving
and long life time. Because standard of bulb-type traffic
signal was established and has been enforced but as stand-
ard of a traffic signal employing such a new light source as
the LED traffic signal is not prepared. Accordingly, for the
purpose of construction of domestic-spread basis of LED
traffic signal, a research for development of Korean-type
LED traffic signal standard has been in progress since 1998
and it is expected that its spread will be soon common in
Korea.
The development of Korean-type LED traffic signal
standard was carried out in such order. First, we analyzed
current standards and technologies related traffic signals
and drew-out temporary standard based on existing traffic
signal standard. Second, we manufactured test traffic signals and evaluated their performances in the laboratory
and outdoor. Third, we developed a draft of the standard
and proposed standard.
Main considerations concerning the standard development are as follows.
• Safety: Safety of the products employing new technologies and materials is essential in order to install and operate them on the spot. Especially, in the case of traffic
signals, as their lighting indicates directions of vehicle's
movement, traffic accidents and traffic safety should be
taken into account above all. A LED traffic signal standard should include test items, test methods, performance and matters regarding its authentication.
• Structural compatibility: A LED traffic signal should
have structural compatibility with existing traffic signals, so that it can replace existing traffic signals by not
deforming or modifying shapes of a housing, a traffic
signal post and a local controller but replacing a traffic
signal module.
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JUNG, JEONG, HAN
Table 1: Main contents of Standard of Korean LED traffic signal (Draft)
Color Boundaries
Red
Luminous Intensity [Cd]
in the reference axis
Yellow
Green
Size
[mm]
Temperature
200
300
-30~70°C
Red Yellow Green
X
Y
x
Y
x
y
0.665
0.335
0.555
0.435
0.009
0.720
0.665
0.335
0.560
0.440
0.284
0.520
0.700
0.290
0.612
0.382
0.028
0.385
0.710
0.290
0.618
0.382
0.183
0.359
Min = 140* (d**=200mm)
Min = 340* (d**=300mm)
* The intensity value is the required value at the point where horizontal and vertical angles are 2.5 degrees from the reference axis.
** d indicates the diameter of the roundel signal head.
• Practicality: Standard value which can embodies maximum performance should be suggested in consideration
of LED production technology, level of circuit design
and technical level of electronic and electrical engineering and optical equipment production. In addition, features of Korean climate and traffic environment, and
citizen's response to the LED traffic signal must be synthetically examined and then reflected on the development of the standard.
D EV E L O P M E N T O F KO R E A N S T A N D A R D ( D RA F T)
A N D D E M O N S T RA T I O N
Based on results of the analyses of existing standards and
the elementary experiments such as proper luminous intensity, environmental adaptation and on-site test, "Standard of Korean LED traffic signal (Draft)" was presented in
early 2001. Afterwards, through opinion collection procedures such as several briefings and public hearings, the
draft was submitted to the authorities concerned such as
the police headquarter and is now under final consideration. Main contents of "Standard of Korean LED traffic
signals (Draft)" are described in Table 1 and, in sum, as follows.
In consideration of technical levels of domestic and international LED light source and characteristics of radiances, criteria for intensity of light according to color are
set identically for three colors as adopted in Europe and
Japan.
In consideration of standard of bulb type traffic signal
and results of the elementary experiment, in the case of
300mm traffic signal, reference axis intensity of light was
proposed 340 cd similar to that of green light-bulb type
traffic signal.
A lens for a traffic signal was supposed to be a transparent lens principally and, if necessary, a colored lens may be
used.
As for a lens on which symbols and words exist, by pasting black cover up on the area of a lens except symbols and
words, color contrast between light-up and light-out
should be enhanced.
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A traffic signal module should operate normally at ambient temperatures of –30°C+70°C, and change in intensity of light should be within ±20% at 25°C.
A traffic signal should operate normally without any abnormality at an allowable voltage( in the case of rated
110V, 88V~121V and in the case of rated 220V,
176V~242V).
A traffic signal should be well wired lest reduction rate of
optical output should exceed 20% even when one malfunction or more than one in light source elements happen.
At the moment when a traffic signal is turned on at a rated voltage and 25°C, electrical power should be below
15W, a power factor over 0.9 and a total harmonic distortion below 40%.
After 5-sec light-on and 5-sec-light-out alternate 50000
times, there should be not any abnormality in operation
status of a LED module.
Free guaranty term for a traffic signal should be 36
months.
After installation of a traffic signal, for the purpose of its
management and maintenance of its performance, a
nameplate on which main performances are written
should be attached.
LED traffic signals fit for suggested the Standard (draft)
were manufactured and have been built and operated at
some crossways of Seoul and Taejon city as test models.
[Fig. 1]. LED traffic signals consumed electrical power of 8
~ 15W according to their colors and areas of radiance and
it is reported that energy saving of 85 ~90% is available. As
a result of questionnaire for citizens, more than 80% of
them answered that luminosity, color and visibility of the
LED traffic signal are greatly superior to those of existing
signals.
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POSTER SESSION
Fig. 1 Scene of installed Full Color LED traffic signals (City
of Taejon, 2001)
Economy of LED traffic signal is analyzed in a way that
payback period is calculated by dividing net initial investment by total annual profit. Here, net initial investment is
a cost require to replace LED traffic signals (C) deducted
by DSM effect (G). Total annual profit is a sum of predictable cost in annual electricity saving (I), in maintenance
and repair saving (J), in environmental improvement due
to reduction CO2 (L). But cost for improvement of traffic
environment (M) which is saved by enhancement of visibility is neglected.
Payback period = (C-G) / (I+J+L+M), M=0
Economical analyses are performed for two cases, that is,
one case where all traffic signals throughout the country
are replace by LED signals and the other case where only
red signals are replaced, which require small initial investment compared to other color signals and have the largest
energy saving potential. Elementary data employed in the
economical analyses are as follows.
A N E C O N O M I C A L A N A L YS I S O F L E D T RA F F I C
• Number of traffic signals: 280,080set / 801,932lamps
- Vehicle: 161,181 set X 3.5 lamps/set = 564,134 lamps
- Pedestrian: 69,655 set X 2 lamps/set = 139,310 lamps
- Others: 49,244 set X 2 lamps/set = 98,488 lamps
SIGNAL
Traffic signals that are widely installed in Korea employ
bulbs and are of 100W/300mm and, 280,080 set/801,932
lamps have been installed and operated throughout the
country currently in 1999. Of them, 58% (161,181 Set),
25% (69,655Set) and 18% (49,244Set) correspond to traffic signals, pedestrian signals and other supplementary signals respectively. It was reported that instant electrical
power consumed by traffic signals amounts to 28MW (annual electricity of 245 GWH) and 20 million EU and 40
million EU are expended as annual electricity fee and
maintenance fee respectively.
• One red lamp is equipped to one set of traffic signals and
among them one lamp is kept light-on
• Ratio of average light-on time of a red signal: 60% (Actually 50~75%)
• Prices of LED signals (estimated)
- Red and yellow 220 EU / green 350 EU / an average
260 EU
Table 2: An Economical analysis of LED traffic signals
Item
Full color
exchange
Red color
exchange
Remarks
A
Number of signals (set)
280,080
230,836
Red includes only vehicular and pedestrian
signals[2]
B
Number of signals (lamps)
882,522
230,836
C
Retrofitting Cost (million EU)
209
51
B x Price of traffic signals
D
Power consumption of bulb-type (kW)[1]
28,008
13,850
A x 0.1kW, Red: A x 0.1kW x 0.6
E
Power consumption of LED-type (kW)[1]
4,201
2,078
A x 0.015kW, Red: A x 0.015kW x 0.6
F
Power plant construction effect (kW)
23,807
11,773
D-E
G
DSM effect (million EU)
48
24
F x 2000 EU/kW
H
Electrical energy saving (GWH/Y)
209
103
F x 24hours x 365 days
I
Saving in electricity (million EU/Y)
16
5
B x 0.085kW x 0.02EU/kW x 12 months
J
Saving in maintenance(million EU/Y)[3]
30
9
Saving 75%
K
Reduction Amount of CO2 (Ton/Y)
173,094
85,596
H x 830 Ton/GWH
L
Saving in CO2 treatment(million EU/Y)
35
17
K x 200 EU/Ton
M
Saving in traffic improvement
-
-
-
N
Payback period
2.0
0.9
(C-G)/(I+J+L+M)
[1] One lamp per one set of signals is always light-on.
[2] One red lamp is attached each set of vehicular and pedestrian signals
[3] Full color exchange: 40 million EU/Y * 0.75. Red color exchange: 40 million EU/Y * 0.75 * 230,836/882,522
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• Average electricity saving: 85% (100W -> 15W)
• Average saving rate in maintenance and repair: 75%
• Electricity cost: 0.02 EU/W-Month (A fixed amount
paid according to capacities of facilities regardless of
consumed electricity)
• DSM effect: 2,000 EU/kW (based on a nuclear power
generator)
• CO2 generation: 830 Ton/GWH (based on 500MW
coal-fired power generator)
• CO2 treatment cost: 200 EU/Ton (currently $100~$300/
Ton)
• EU rate: 1,146 Won/EU
Table 2 summarizes procedures of economical analysis,
and it is shown from the analysis that payback periods are
about 2 years for the first case and 0.9 years for the second
case and accordingly economy of
LED traffic signals is significantly excellent.
CO N C L U S I O N
It is the worldwide trend that spread of a LED traffic signal is being expanded due to such advantages as its significant energy saving, a long life and improvement of traffic
environment by high visibility. However, because safety is
prior to other factors of traffic signals, its widely spread is
now impossible in Korea where any institutional standard
of LED traffic signal does not exist yet.
In this paper, technical trends and standards concerned
foreign LED traffic signals were analyzed, and after sample
products were manufactured and evaluated in consideration of compatibility with existing traffic signals, and then
standard of LED traffic signal fit to Korean environment
was presented. LED traffic signals manufactured according
to the suggested standard have been installed and operated
as test models on real roads in Seoul and Taejon city. And
it is expected that the standard will be established sooner
or later, and wide range of spread of LED traffic signal will
be possible.
As technologies of semi-conductor light source keep
growing rapidly, suggested specifications may not be suitable for near future. Therefore, it is thought that continuous research and development directed toward fully taking
advantage of LED technologies.
RE FE R E N C E S
B. M. Jung and H. G. Jeong, A study on specifications and
standard system for energy efficient LED traffic signals,
A research report of Korea Institute of Energy Research,
2001.
Institute of Transportation Engineers, Interim LED
Purchase Specification, 1998.
European Committee for standardization, Traffic Control
Equipment – Signal Head, EN12368, 2000.
CIE Technical Report, A Guide for the Design of Road Traffic
Lights, 1988.
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