Survey on How the Large Outdoor LED Panels at Road Intersections Affect Drivers by Yuqian.chen

Abstract _______________________________________________________2

References________________________________________________________21 Appendixes _______________________________________________________22

【 Table of Contents

1 Introduction ____________________________________________________2 1.1 Survey background ………………………………………………………2 1.2 Survey objectives and significance …………………………………………4 1.3 Definitions of related concepts ……………………………………………4 2 Survey Design___________________________________________________5 2.1 Pre-survey ……………………………………………………………5 2.2 Survey scope ……………………………………………………………5 2.3 Survey objects and content …………………………………………………5 2.4 Survey methods …………………………………………………………6 2.5 Survey flow ………………………………………………………………7 3 Survey Results and Analysis_________________________________________7 3.1 Distribution of the large outdoor LEDs in Heping District ……………………7 3.2 Survey analysis targeted at different groups of people ………………………8 3.2.1 Analysis of drivers‟ feelings of large outdoor LEDs …………………8 3.2.2 Analysis of related populations‟ application of large outdoor LED ……11 3.3 Analysis of the field measurement of typical large outdoor LEDs ……………13 3.3.1 Analysis of the spatial features of typical large outdoor LEDs…………13 3.3.2 Analysis of the optical properties of typical large outdoor LEDs ………15 4 Suggestions for Planning and Administration____________________________19 4.1 Suggestions for the planning and administration of large outdoor LEDs ………19 4.2 Suggestions for large outdoor LEDs‟ spatial settings…………………………19 4.2.1 The ideal space model at intersections………………………………19 4.2.2 Particular cases……………………………………………………20 4.3 Suggestions for the adjustment of large outdoor LEDs‟ optical properties………20

】

【Abstract】 “When I turned, my eyes were blurred

With the wide popularity of electronic screens, large outdoor LED panels have sprung up like mushrooms, which brings new troubles like light pollution and visual disturbance to residents while

by the colorful image. I could see nothing and the accident happened” ——Mr. Wei in Shenyang

lighting the sky. Taking the Heping District of Shenyang Province as an example in this survey, the quantitative analysis of the spatial features and optical properties of the typical large outdoor LED panels at road intersections through field observations, together with the qualitative analysis of the subjective feelings of drivers and related groups through questionnaires and interviews, reveals the influencing laws and characteristics of these LED panels on drivers, thereby providing a reference for the scientific and reasonable setting of large outdoor LED panels.

【Key words】 Road intersections

“These LED advertising panels are not obvious during the day, but the light dazzles eyes at night. For drivers in particular, strong light tends to make them suffer from temporary „blindness‟”. ——Xiao Hong, a member of

Shenyang

Political

Consultative

Committee

Large outdoor LED panels

Drivers

1 Introduction 1.1 Survey background The application of large outdoor LED panels (hereinafter referred to as LEDs) in business districts has once created bright night scenery in cities. On the other hand, however, potential security problems resulting from LEDs are on the increase (Fig.1). Fig.2 CCTV Morning News report

According to incomplete statistics, in the recent five

years, a total of 434 reports online have covered the social problems caused by LEDs, 275 of which Fig.1 News report of LED

are about the traffic safety related to LEDs. And the CCTV Morning News program even reported the LED-incurred traffic accident in Shenyang in March, 2014 (Fig.2). At present, many countries abroad have made a lot of researches on LEDs‟ influence on traffic safety and formulated a series of laws, regulations and policies to mitigate the influence to a minor degree, which is shown in Tab.1: Tab.1 Foreign regulations on LEDs Country United States New South Wales, Australia

QLD, Australia

Sweden

Regulations In the U.S., many federal regulations ban the setting of electronic displays at road intersections. Advertising signs are generally 152m-305m away from road intersections. The National Environmental Policies and Regulations 64—Advertisements and Signs Bill formulated a set of evaluation indexes for outdoor advertisements in 2001. The evaluation criteria include the position to set advertisement signs, variable information signs, dynamic signs, electronic signs of videos and flash, brightness and reflectivity, collision records and the content of signs. In 2002, the Guidelines for Setting Advertisements on Road Sides pointed out that hidden traffic dangers are generally associated with advertising signs‟ size, location, brightness, background and their distance from roads. Meanwhile, regular changes of ads‟ content are more likely to attract drivers‟ attention than static and famous signs. The following two aspects are recommended to be controlled: a) Location of advertisement signs, including both horizontal and vertical control; b) Physical properties of ads, such as shape, brightness, color and font size. The outdoor electronic displays‟ ad information must be simple and clear. Ad texts must be as short as possible, without numbers or websites. Ad signs are prohibited to be set parallel to roads.

Some economically developed large and medium-sized cities in China (such as Beijing, Shanghai, Shenzhen, Shenyang, etc., See Tab.2) have also introduced corresponding regulations on

Below are the provisions of Specifications on the Administration of Outdoor Electronic Display Settings in Shenyang.

“The brightness value of the outdoor electronic displays set in and around business districts should not be more than 1000cd /m2 while the value of those set in other areas should not be more than 400cd/m2.”

“For those electronic displays set on both sides of urban main roads, excluding closed squares and pedestrian streets, dynamic images are forbidden. In principle, each fixed image should last for more than 5 seconds and the images should be switched slowly.”

the administration of outdoor electronic displays. Tab.2 Domestic regulations on LEDs City

Regulations

Beijing

Specifications on the Administration of Outdoor Electronic Display Settings in Beijing (2008)

Nanjing

Specifications on the Administration of Outdoor Electronic Display Settings in Nanjing (2009)

Shenzhen

Special Plans for Outdoor Electronic Display Settings in Futian, Luohu, Nanshan, Yantian and North Stations districts in Shenzhen (2012)

Shanghai

Limits and Measurement Methods of LED Panelsâ&#x20AC;&#x; Brightness in Public Areas (2013)

Shenyang

Specifications on the Administration of Outdoor Electronic Display Settings in Shenyang (2014)

Although related departments of both foreign and domestic cities have enacted substantial provisions on the setting of LEDs in cities, LED-related problems still emerge in an endless stream due to their poor feasibility. A survey will be conducted from qualitative and quantitative aspects to find out the fundamental reason why problems still exist after the enactment of related provisions.

1.2 Survey objectives and significance In spite of the numerous regulations on LEDs settings in various cities in China, the vast majority of residents still complain a lot about the LEDs erected by the road. As illustrated by an increasing number of reports, the visual impact caused by the existing LEDs is prone to induce traffic accidents. All these have proven that problems still exist in the setting and administration of LEDs at the present stage.

Fig.3. Prevalent LEDs at night

To find out the essence of this social problem, we make a correlation analysis of the factors through which LEDs affect driving by investigating the problems concerning the use and control of LEDs. The effective solutions obtained are of reference value to the future administration of LEDs, the improvement of traffic safety in urban areas and the enhancement of driving comfort.

1.3 Definitions of related concepts

[1] Lu Qingrong, Brief description of LED panels’ industrial standards and

1) Large outdoor LED panels

implementing situations, Chinese Journal

Outdoor LED panels refer to the screens set on buildings‟ roofs, in front of the gates, or along the road of business districts to display ads. In this investigation, the objects more than 30m2 are

of Liquid Crystals and Displays, No.6, 2007

defined as large outdoor LED panels [1]. 2) LEDs’ optical properties The important parameters measuring whether LEDs‟ optical properties are normative or not, include brightness, dynamic flickering, color temperatures and contrast ratios

[2]

[2] Electronic area standard of the People‟s Republic of China, Generic specification for LED panels (SJ/T11141—2003)

2. Survey Design Non-motor

Automobile

vehicle drivers

drivers

Pedestrians

2.1 Pre-survey Tab.3 Pre-survey content

Objects

Automobile drivers

Questions

Non-motor vehicle drivers

Pedestrians Pre-survey Objects

1. Does LED affect you?

Most think so.

2. How does LED affect you?

Too bright and dazzling to see the signs on roads.

3. In the Heping district, which LED impresses you most?

Most choose those in Maluwan, followed by Taiyuan Street and Wanhao.

Most donâ&#x20AC;&#x;t think so.

The vast majority donâ&#x20AC;&#x;t think so.

Random Shenyang

Pre-survey

sites

methods

interviews at streets

Fig.4 Pre-survey schematic diagram

Through pre-survey (Tab.3), we determine automobile drivers as future objects, brightness and dynamic flickering as indicators, and Maluwan, Taiyuan Street and Wanhao as the typical sites.

2.2. Survey scope The Heping District in Shenyang Province is selected as the survey site, covering the west of Youth Street and Beijing Street, the east of Victory Street, the south of Banpingshan Road and the north of Hun River. As a core economic zone in Shenyang, Heping District is characterized by typical crowded population as well as traffic, and a large number of LEDs (Fig.5). Fig.5 District map of survey scope

2.3 Survey objects and contents After topic is decided, the survey objects and contents are further determined by field survey and questionnaires; including such five parts as A, B, C, D and E. Survey Objects

Survey Contents

A．LEDs‟ spatial features

Distribution

Quantity

Area

B. Typical LEDs‟ optical properties

Brightness

Dynamic flickering

Contrast ratios

C. LED users D. LED administrators E. Vehicle drivers

Situation of using LEDs

Light colors

Situation of administrating LEDs Drivers‟ basic information

Subjective feelings

2.4 Survey methods 1) Literature survey We searched the Internet and library to collect the current domestic and foreign researches and relevant specifications regarding LEDs‟ influence on drivers so as to lend theoretical support to the survey report. 2) Field measurement Field measurement of optical properties aims at gathering the data of optical properties for the further verification of whether the large outdoor LEDs are in accordance with the specifications in Shenyang so that problems can be discovered (Fig.6).

Fig.6 Photo of field measurement

3) Questionnaires To get a more accurate understanding of LEDs‟ influence on drivers from various aspects, questionnaires were distributed at particular road intersections and randomly given in other sites, the main objective of which was to investigate the influence on taxi, bus and private car divers by the LEDs in Heping District at night (Fig.7). 4) Interviews Through the face-to-face communication with LEDs users and administrators, interviews were Fig.7 Photo of distributing questionnaires

adopted for a comprehensive understanding of their opinions on and suggestions for LED settings.

2.5 Survey flow Preparation

Preliminary

Further study

phase

study phase

phase

Final report phase SPSS analysis data

User Questionnaires

Related news reports

& interviews s

DeterField exploration

Put forward the

Subject

mine

Deter-

survey

mine

Related literatures signifi-

argumen& regulations tation

subject Experts‟ guidance

s Administrator

Pre-survey

survey

cance

objects

objectives

analysis

data analysis

Sort out

Information

sions

analysis

Detailed survey

SuggesLEDs‟ spatial Field measurement

Fig.8 Flow chart of survey

Experimental

Conclu-

Literature survey methods

& suggestions

Correlation

Drivers

features

Spatial distribution Spatial features Brightness

LEDs‟ optical properties

Dynamic flickering Light colors Contrast ratios of colors

tions

Complete

analyze

the

survey

report

results

3. Survey Results and Analysis 3.1 Distribution of the large outdoor LEDs in Heping District There are 22 LED panels distributed in 16 sites in the Heping District of Shenyang Province. Such panels are mostly located around main roads with a relatively large traffic flow, rarely at branch intersections (Fig.9). Generally, only one LED is set at one intersection. In the surroundings of large business districts, however, more LEDs can be seen (Tab.4 and 5).

Fig.9 LEDs distribution in Heping District

3.2 Survey analysis targeted at different groups of people 3.2.1 Analysis of drivers’ feelings of large outdoor LEDs 1) Analysis of questionnaires’ basic information Questionnaires were distributed at four fixed sites and one random site, with 40 at each and 200 in total. And 189 questionnaires were valid. Most of the drivers had driven for more than a year and 60% for more than five years. The vast majority were private car drivers, with male drivers

Tab.4 LED quantity at intersections Road grade at intersections

Quantity

Main road-main road

Main road- secondary road

Main road-branch

Branch-branch

accounting for a larger proportion. Over 80% were ordinary population and non-sensitive population.

Tab.5 LEDs‟ areas and quantities

2) Analysis of large outdoor LEDs’ influence on drivers

Area of LED panels

(1) Analysis of large outdoor LEDs’ influence on drivers in different areas

30m2—99m2

According to the statistics, the LEDs in Maluwan exerted the greatest impact on drivers‟ attention and the LEDs in Wanhao most greatly affected drivers‟ recognition capability. Drivers were less affected by LEDs in other areas.

LED quantity 4

100m —199m 200m —299m 300m —399m 2

≥400m

(2) Analysis of large outdoor LEDs’ overall influence on drivers As shown by the statistics, those believing that LEDs affected their attention and recognition capability accounted for 80% and 70%, respectively. Most people thought that LEDs most greatly affected the recognition of pedestrians crossing roads and bicycles, followed by the recognition of signal lights (Fig.10). Traffic accidents were quite likely to be induced in Shenyang where roads tended to be frozen in winter. 【Summary】: The comprehensive statistics show that the LEDs in Maluwan affect drivers most greatly, accounting for 76.32% of the total, followed by those in Shengjing Hospital and Municipal Square,

Fig.10 Traffic factors affected by LEDs

making up 86%. It can be seen that a wider range of areas are affected at night by the LEDs at road intersections, which is a problem urgently needed to be solved (Fig.11).

Fig. 11 LEDs‟ overall influence on drivers

3) Analysis of how the large outdoor LEDs’ quantity and optical properties affect drivers (1) Analysis of to what degree brightness and dynamic flickering affect drivers

Fig.12 Influence of LEDs‟ brightness and dynamic flickering on drivers

Brightness and dynamic flickering were the two most important factors we investigated. As indicated by the statistics results, a large gap existed between brightness and people‟s subjective feelings, with more than 85% considering the brightness to be somewhat dazzling and 85% feeling uncomfortable with dynamic flickering. Thus, proper measures should be taken to control the brightness according to most people‟s feelings (Fig.12). (2) Analysis of light color’s influence We had expected red and yellow light to be the most uncomfortable, but the statistical results

Fig.13 Influence degree of LEDs‟ light colors

showed that red and white light exerted the greatest influence on drivers due to their high brightness (Fig.13). Therefore, we should properly control the panels‟ main colors. (3) Statistics of to what degree LEDs quantity at road intersections affect drivers According to the subjective statistical results, 75% thought they were affected, 40% of whom felt slightly affected (Fig.14). We found through investigation and analysis that the main reason could be attributed to the relative position relationship between drivers and LEDs. In general, drivers were only affected by one or two LEDs set in the way ahead, regardless of the LED quantity at the road intersection. (4) Statistical analysis of the factors through which LEDs affect night driving The statistics showed that dynamic flickering affected drivers to the greatest extent, chosen by 130 people, followed by brightness chosen by 100 people. In comparison to these two factors, the rest ones exerted smaller influences, only selected by 15 to 40 people. 【Summary】： As can be seen from the statistical data, dynamic flickering and brightness are the two most

Fig.14 Influence of LED quantity at intersections on drivers

important factors affecting drivers, which should be considered as the key points during control. Influences of the rest factors are relatively smaller. The quantity of LEDs at the same intersection influences drivers to a minor degree, verifying the above-mentioned statistical results of to what degree LEDs quantity at road intersections affect drivers (Fig.15).

4) Questionnaire correlation analysis

Fig.15 Influence of LEDs‟ impact factors on drivers

Tab.6 Correlation analysis between impact factors and subjective feelings Gender Attention Recognition

-0.04748 0.0410242

Age -0.08779 0.0177583

driving years

Education background

Sensitive groups

Brightness

-0.03141 0.0026781

0.026089 -0.026322

0.169615 0.195011

0.556516** 0.5966012**

Dynamic flickering

LED quantity at

0.55419** 0.64792**

0.41627* 0.57162**

intersections

ability

Using the principal component analysis of SPSS software (Tab.14), we reached the following conclusions. First, LEDs‟ high brightness and dynamic flickering disturbed drivers to a certain degree. And then, LED quantity at road intersections showed a low correlation with attention dispersion but a significant correlation with recognition ability. Drivers would only see the panels ahead, LED quantity, therefore, displayed a weaker relationship with attention dispersion when compared to brightness and dynamic flickering. As LED quantity affected the light environment at road intersections, it was directly related to and greatly affected recognition ability, conforming to the scientific reasoning.

Note: In general, r and p signify sample‟s correlation coefficient and population‟s correlation coefficient, respectively. The calculation formula of correlation coefficient varies from variable to variable. The simple Pearson correlation coefficient is commonly used in the relevant analysis, calculating the continuous data at fixed distances. The properties of the widely-used Pearson correlation coefficient are shown below. ︱r︱<0.3————Weak correlation 0.3<︱r︱<0.5——low correlation 0.5<︱r︱<0.8——significant correlation 0.8<︱r︱<1———high correlation

5) Summary of questionnaire feedback We got a lot of feedback during investigation, including rational and extremely unreasonable opinions. But on the whole, it reflected that this was indeed a problem that needed to be urgently solved. The feedback summary was shown in the following (Tab.7). Some meaningful and feasible suggestions were extracted from the feedback, for example, applying the principle of automatically adjusting brightness according to the phone screen to LED could address brightness-related problems in a cost-effective way.

6) Analysis and summary of questionnaire results We got to understand how drivers felt about the brightness and dynamic flickering of the LEDs at road intersections and to what degree these factors affected driving by analyzing the questionnaires‟ feedback information. And the following conclusions could be reached. Ads‟ content is also

1. Most drivers‟ attention

2. LEDs‟ brightness and

3. LEDs mainly affect the

and recognition ability

dynamic flickering deviate

recognition of pedestrians

an important factor

are affected by LEDs.

greatly from people‟s

crossing roads and

affecting drivers.

subjective feelings

bicycles.

When distributing questionnaires, we also noted that private car drivers and taxi drivers showed a big difference in terms of their subjective feelings of LEDs. Private car drivers tended to be more negative about large LEDs‟ visual impacts. In their eyes, LEDs‟ brightness appeared to be more dazzling and more likely to cause distraction during driving.

3.2.2 Analysis of related populations’ application of large outdoor LEDs 1) Analysis of how large outdoor LEDs are used Q：Do you understand the requirements for LEDs‟ content and image forms?

A：Not involving politics is the only requirement. We check the content on our own.

Q1：Are there any specific requirements for setting LEDs, such as space and the panels‟ brightness?

A1 ： Considering the viewing effects, we‟d better set them in the areas with high traffic and human flows and put the panels perpendicular to roads.

Fig.16 Interview of LED advertisement designers

LED advertisers Q2 ： What negative influences do you think LEDs exert on cities?

LED exhibitors A2：The noise and brightness may affect residents‟ life and city image.

【Summary】: After interviewing two groups of users, we find that only a few limitations are set on what LED advertisers should display while the exhibitors always emphasize their own economic interests. According to the exhibitors, it is much better when LEDs are brighter at night and located at more crowed areas, ignoring the potential security problems in urban traffic brought by LEDs. 2) Analysis of the situation of how administrators regulate large outdoor LEDs

Fig.17 Interview of LED administrators

Q1：How does your department comply with the specific indicators of optical properties stipulated by the newly formulated LED regulations in

Shenyang, such as LED brightness?

Q2：Which departments need to examine and approve LEDs‟ A1: Due to various constraints, we can

settings in Shenyang?

only demand businesses to adjust LED brightness to a soft state according to residents‟ complaints to minimize the

A2：Mainly the urban management departments. But the broadcasting and

negative effects.

TV office, national telecommunications and information administration, transportation bureau and urban management departments can also conduct

LED administrators

Q3：In general, how long does it take to get the feedback of the overall

situation of LED displaying in Shenyang?

an approval record of LEDs‟ settings.

A3：No specific time. Check particular LEDs when the citizens complain about them.

【Summary】: We discover from the communication with LED administrators that despite the promulgation and implementation of the regulations on LEDs‟ reasonable settings at the beginning of this year in Shenyang, many problems still exist, such as the fragmented regulatory framework, multiple but non-unified LED administrative departments, regulation blind spots, lack of regulation on the LEDs inside cities, difficulty in law enforcement and uncertain regulation time.

3.3 Analysis of the field measurement of typical large outdoor LEDs 3.3.1 Analysis of the spatial features of typical large outdoor LEDs A

Number of typical sites Name of Intersections Road

Intersection between Heping Intersection between Sanhao

Intersection between Youth

North Street, Heping South

Street and Wenhua Road

Street and Zhongshan Road

Street, Guangrong Street,

(Shengjing Hospital)

(Municipal Square)

Zhonghua Road and Shiyiwei Road (Maluwan)

Intersection between Nanjing North Street, Nanjing South Street and Zhonghua Road (Taiyuan Street)

Intersection between Youth Street and the Second Ring Road (Wanhao)

Street features

Business district

Road grade

Main road-Main road

Main road-Secondary road

Main road-Main road

Main road-Branch

LED quantity

LED number

LED screen area

272 m2

LED Panelâ&#x20AC;&#x2122;s suspension height

Environmental characteristics at intersections

Field photos

A2 130 2

224 m2

150 m2

91 m2

15m

10m

C1 580 m2

150 m2

663 m2

168 m2

150 m2

663 m2

10m

22m

12m

10m

11m

According to the statistics, the majority (10/11) of typical LEDs covered an area over 100 ㎡, with two reaching as large as 600 ㎡, so a wide range of areas were affected. The height of most typical LEDs (7/11) was below 10m, and the backward distance of most typical LEDs (8/11) was less than 15m, which exerted a large impact on drivers because it was close to their visual field.

When analyzing the influence of typical LEDs in different spaces, we tried to find out the major influencing factors by conducting a correlation analysis between people‟s subjective feelings and the measured data at the road intersections where the questionnaires were distributed (Tab.8). Fig.18 Multiple interferences under complicated traffic conditions

Tab.8 Correlation between spatial features and drivers’ subjective feelings dissatisfaction dazzling discomfort LED quantity

Maluwan

Municipal Square

degree

at intersections

0.92

0.87

0.86

0.92

dissatisfaction dazzling discomfort LED quantity

Shengjing Hospital Wanhao

degree

at intersections

0.84

0.78

0.89

0.85

0.79

0.72

Questionnaire results showed that people exhibit the deepest feelings of the LEDs in Maluwan. Through comparative analysis, it was found that such measurement parameters as LED quantity and the area of a single panel were not the most prominent among these intersections. What was the most different was the complicated traffic conditions here (Fig.18).

The convergence of traffic flow from five directions formed a four-way intersection and two Y-shaped intersections here, with one-way traffic lanes and public buildings featuring a large passenger flow. Intricate traffic and passenger flow, together with the complicated traffic conditions Fig.19 Interference at normal intersections

and LEDs‟ locations, disturbed drivers for multiple times here (Fig.19 and 20). Drivers‟ viewpoint height

Cantilever-type

Panel‟s suspension height

1.2m

traffic lights 6m

15m

65m

118m

Fig.20 Analysis diagram of distraction

Brightness grade Brightness value （cd/㎡） Low brightness

1-400

Medium brightness

400-1000

High brightness

above 1000

Fig.9 LED brightness grades

3.3.2 Analysis of the optical properties of typical large outdoor LEDs 1) Analysis of the measurement results of typical large outdoor LEDs‟ brightness According to the established measuring method, we measured typical LEDs‟ brightness and conducted a statistical analysis (Fig.21), deriving the mean, maximum value and minimum value of brightness shown in Fig.18. And then, we carried out a statistical analysis of typical LEDs‟ brightness distribution interval according to the three levels of brightness (Tab.9, Fig.22). Fig.22 Distribution interval of typical LEDs‟ brightness values

Fig.21 Typical LEDs’ brightness values at test points

As the statistics suggested, 27% typical LEDs were mostly characterized by high brightness, seriously exceeding the standard ranges. Meanwhile, typical LEDs‟ brightness level showed a great difference.

2) Analysis of the measurement results of typical large outdoor LEDs’ dynamic flickering For those LEDs with the same brightness mean, the brighter the dynamic flickering was the greater harm it did to drivers. The lack of quantitative indicators in academic circles and the

Fig.23 Contrast between transient brightness variations and dynamic flickering with the same brightness mean values

industry made it impossible to normalize transient variation of LEDs‟ brightness. Range, standard deviation and dispersion coefficient, which were widely used in statistical data processing, were adopted to reflect the transient variation of LEDs‟ brightness in this survey.

Index name computing method

However, after statistical analysis, we found that these three indicators could not fully reflect the situation, so we put forward fluctuation value and fluctuation coefficient to reflect typical LEDs‟ dynamic flickering.

Fluctuation value

Take the typical LEDs C2, A3 and A1, D1 in Fig.23 as an example. The brightness mean of the

Function

The square root of the

Reflect the

arithmetic mean

transient

derived from the

brightness

deviation square of the variations of former value and the

typical LED

latter value

screens

former group was about 340cd/㎡, while the latter one was approximately 1200cd/㎡. The transient variation of LEDs‟ brightness varied greatly in these two groups, with C2 and A1 showing obvious

The square-mean ratio of the arithmetic

greater variations. We carried out a statistical analysis of typical LEDs‟ transient fluctuation values and fluctuation

Fluctuation

means derived from

coefficient the deviation square of the former value and

coefficients based on the data obtained from field measurement (Fig.21, Tab.10).

the latter value

Reflect the brightness variations and dynamic flickering degree of typical LED panels

Tab.10 Typical LEDs‟ fluctuation coefficients Number of

Mean value of LEDs

Fluctuation

Mean value of LEDs

Fluctuation

（cd/㎡）

coefficient

（cd/㎡）

coefficient

1108

0.55

347

0.62

1719

0.36

504

0.63

336

0.38

1338

0.36

518

0.67

403

0.59

2359

0.18

415

0.84

557

0.66

LEDs

Number of LEDs

25 20 15 10 5 0 A1 A2 A3 B1 B2 C1 C2 C3 D1 D2 E 0-400

400-1000

>1000

As shown by the statistics, nearly half of the typical LEDs had large transient fluctuation values and fluctuation coefficients. People complained a lot about the extremely dazzling panels, especially the No.1 panel in Maluwan and the No.2 panel in Taiyuan Street. In a word, adjustments were urgently needed. 3) Analysis of the measurement results of typical large outdoor LEDs’ colors Using the Google image color principle, we divided LEDs‟ main colors into seven series, including red, orange, yellow, green, blue, purple and white. Taking as an example the C2 panel in Taiyuan Street, we recorded the panel‟s pictures every 4 seconds and the process lasted for 3 minutes. And then, we analyzed the pictures‟ main colors images, as shown in Fig.25 and Fig.26.

Fig.26 Proportion of LED‟s each color light in the total

Fig.25 Example of analyzing the colors of C2‟s continuously-shooting photos

Below was the statistical analysis of the main colors of 11 panels and 495 photos. As shown in Fig.27, the main colors of each panel varied greatly. On the whole, white, blue and red made up the largest proportion, accounting for 83% of the total. The results of questionnaires indicated that red, white, yellow and blue, had the biggest influence on people, accounting for 85% of the main colors. So this factor was in desperate need of control. 4) Analysis of the measurement results of typical large outdoor LEDs’ contrast ratios

Fig.27 Statistical analysis of different panels‟ colors

We chose five typical sites in Heping District of Shenyang Province to measure their background environment‟s brightness (see appendix) and calculated the BLR values to measure whether the LED brightness here was moderate (Tab.11). Since outdoor brightness was affected by multiple complicated factors, we conducted the measurement in each area for several times at the nights of common weather in Shenyang, namely, a fine day with slight dusts. Tab.11 Typical LEDs‟ BLR values Site

average

A Shengjing

B Municipal

Hospital

Square

Maluwan

Taiyuan Street

Wanhao

9.26

0.47

1.76

2.23

0.39

16.23

30.35

12.94

28.88

10.51

brightness BLR

It could be seen from Tab.12 that the brightness of LEDs‟ background environment ranged from a few tenths of cd/m2 to a few cd/m2 while LEDs‟ average brightness reached hundreds or even thousands of cd/m2, displaying a large difference. And the BLR values in Taiyuan Street and

Note: BLR is the evaluation scale of apparent brightness. BLR=24 log（L panel brightness/L 0.35 ）- 17 background brightness

the Municipal Square were above 20, indicating a relatively brighter level. The brightness levels of Tab.12 Relationship between BLR values and subjective evaluations

the rest three areas were moderate. 【Summary】

BLR value

subjective evaluations

≤0

too dark

relatively dark

moderately bright

the LEDs display too strong dynamic flickering, with the fluctuation coefficient over 0.5. Finally,

relatively brighter

partial LEDs‟ main colors are white and red. The brightness is raised to a rather high level as a

≥40

too bright

The following three conclusions can be reached by sorting out and analyzing the data obtained from the field measurement of typical large outdoor LEDs. First, most LEDs‟ brightness is above the standard level and the minimum value of some is above the specified value. And then, half of

result of these extremely pure colors. All these have negatively affected drivers. The deep-rooted reasons can be divided into the following aspects through the analysis and summary of this survey. 1. The strategy of not affecting LEDs‟ advertising effects while guaranteeing driving safety has not been worked out yet.

2. Poor administration of LEDs‟ optical properties

3. Lack of quantitative indexes to measure LEDs‟ dynamic flickering, making it difficult to become standardized and reasonable.

4. Imperfect regulations, without specifications on LED panels‟ colors

These problems involve the study and administration of LEDs, so the settlement depends on the study of the proper parameters of LEDs‟ optical properties and the standardized administration of LEDs‟ settings. As these factors‟ impacts on drivers may do harm to driving safety and men‟s life, it is pressing to study LEDs‟ proper parameters and reasonable settings.

4. Suggestions for Planning and Administration 4.1 Suggestions for the planning and administration of large outdoor LEDs We need to consider from the perspectives of advertising designers, exhibitors and regulators to build a good LED planning and administration system. LED advertising designers: When designing advertisements, designers should consciously select the appropriate content, such as avoiding flash, videos and those sensitive ads like the underwear campaigns.

LED exhibitors: When setting properties, exhibitors should strictly abide by the requirements of relevant specifications to control LEDsâ&#x20AC;&#x; spatial settings and optical properties. In addition, they need to

Fig.28 Relationships between LED designers, exhibitors and administrative departments

maintain the screen quality all the time in case low quality LED screens cause frequent flickering.

Regulators: Guarantee the consistency between supervision departmentsâ&#x20AC;&#x; regulations and the relevant specifications executed by local departments to avoid a fragmented regulatory framework. Strengthen the supervision and control of the LEDs located within cities, requiring every LED to register the Outdoor Advertising Registration Certificate to achieve the one-on-one parameterized control and administration. Design reasonable regulating ways and regularly supervise in a planned manner. The LED planning department and administration department should be Fig.29 Ideal plane model of LEDs at intersections

combined into one. Besides, in terms of the play time, the northern areas and southern areas are suggested to set the time before 10pm and 11pm, respectively because of their difference in nightlife. 4.2 Suggestions for large outdoor LEDs’ spatial settings 4.2.1 The ideal space model at intersections Corresponding requirements Quantity

not more than 2 LED panels

Panel’s suspension height

not less than 15 meters at intersections

Area of panels

not more than 30% of the building‟s area

Direction of setting

LED panels should be set along roads, with the image faces the walking directions

Fig.30 Ideal vertical model of LEDs at intersections

4.2.2 Particular cases The LED settings under com plex traffic conditions should not be treated in the same way, but be evaluated and considered separately. For example, attention should be paid to the relative

space position between LEDs and traffic signals at Y-shaped intersections to avoid the overlapped projection of drivers‟ visions, traffic signals and LEDs.

√

Fig.31 Schematic diagram of special space handling

Fig.32 Suggestions for switching LED images

4.3 Suggestions for the adjustment of large outdoor LEDs’ optical properties

According to the analysis and summary of questionnaires‟ results, measured data and spatial settings, we divide the control of LEDs‟ optical properties into the following three aspects.

References: [1] Electronic area standard of the People‟s Republic of China, Generic specification for LED panels (SJ/T11141—2003) [2] Shanghai local standards, Shanghai Ambient (Decoration) Lighting Specifications (DB31／T316—2004) [3] Shenyang local standards, Administration of Outdoor Electronic Display Settings in Shenyang, 2014 [4] Yu Tingting, Study on how large LEDs at intersections affect drivers’ vision at night, Tianjin University, 2011.

[5] Liu Gang, Yu Tingting, Dang Rui and Song Mingjie, Research and analysis of LEDs’ lighting situation at intersections in Tianjing at night, China Illuminating Engineering Journal, No.3 2012 [6] Fang Jing, Xiao Hui and Bing Heliang, Light pollution in cities— thoughts on LEDs’ brightness, China Illuminating Engineering Journal, 2013 Supplement [7] Lu Long, Scheme design of adjusting ambient brightness and LED panels’ brightness, Advanced Display, No.140, 2012 [8] Li Qian, Pan Jiangen, Method of accurately measuring LED panels’ optical properties, Advanced Display, No.140, 2012 [9] Wang Jian, Zhao Minglong, Influence of drivers’ visual features and psychological factors on traffic safety, Henan Science & Technology, Second half of 2010 [10] Xi Yucheng, Chen Xuesong, Limitations on LED panels’ light pollution in public areas, Domestic Unity Issue Number CN31-1424/TB, No.237, 2013 [11] Xu Wenhong, Zhuang Meilin, Yang Yongcheng and Cao Min, Study on the evenness of LED street lights’ color temperature distribution, China Light & Lighting, No.1, 2012 [12] Lu Qingrong, Brief description of LED panels’ industrial standards and implementing situations, Chinese Journal of Liquid Crystals and Displays, No.6, 2007 [13] W.Kurdthongmee. Design and implementation of an FPGA-based multiple-color LED display board [J].engineering science, 2009, (29):327-336

Appendix I

Survey on Outdoor LED Panels’ Impact on Night Driving Safety at Intersections Date: Place: We are the students of Shenyang Jianzhu University. Considering that the large electronic panels (hereinafter referred to as LED panels) exert an increasingly significant influence on driving security at night, we try to figure out to what degree the LED panels and the related impact factors affect driving safety at intersections through this survey. This survey is only for our study. You may rest assured that your personal information is confidential. Thank you for your cooperation! Gender: Male□ Female□ Age: 18-29 □ 30-49 □ above 50 □ 8. Do you feel uncomfortable with the LED panels‟ dynamic flickering 1. What‟s your education background? A. Below senior high school B. Senior high school (including technical secondary school) here? A. Extremely uncomfortable B. Relatively less uncomfortable C. Undergraduate (including junior college) D. above undergraduate C. Slightly uncomfortable 2. What‟s the type of your vehicle (classified by purposes)? D. No uncomfortable feelings E. Relatively comfortable A. Private Cars B. Buses C. Taxis D. Others 9. Does the LED screen quantity at intersections affect you? 3. How long have you been driving? A. Significantly affected B. Relatively less affected A. Less than one year B. 1-5 years C. 5-10 years D. above 10 years C. Slightly affected D. Basically not affected E. Not affected at all 4. How often are you affected by external interferences when doing things at ordinary 10. Which light colors of LED panels do you feel most uncomfortable times? with? (You may choose more than one option) A. Always B. Often C. Occasionally D. Rarely E. Never A. Red B. Yellow C. Blue D. Green E. Orange 5. Will LED panels distract your attention from driving at night? F. Purple G. White A. Significantly distracted B. Relatively less distracted C. Slightly distracted 11. Which of the following LEDs‟ impact factors affect you most during D. Basically not distracted E. Not distracted at all night driving? (You may choose more than one option) 6. When driving at night, have you recognition ability affected by the LED screens here? A. Panel brightness B. Dynamic flickering C. Image colors A. Significantly affected B. Relatively less affected C. Slightly affected D. Several LEDs E. Panel size F. Panel‟s suspension height D. Basically not affected E. Not affected at all G. Others_______ If A/B/C is chosen, your recognition of which items have been affected by LED panels? 12. What suggestions would you put forward for setting LED panels at (You may choose more than one option) intersections? Or what improvements would you like to see? A. Traffic signs B. Traffic signal lights C. Pedestrians and bicycles __________________________________________________________ D. Turning vehicles E. Others __________ __________________________________________________________ 7. Do you think the LED panels here dazzling? A. Extremely dazzling D. Basically not dazzling

B. Relatively less dazzling E. Not dazzling at all

C. Slightly dazzling

Appendix II: Field measurement instruments and principles 1) Principles of selecting typical samples The typical sampling method was used in this survey to select the intersections where LED panels will be investigated, mainly according to drivers‟ collective opinions and the LED quantity at intersections. A total of five typical intersections were finally chosen. Among them, two intersections have 3 LED panels, two intersections have 2 LED panels and one intersection has one LED panel.

Fig. a Photo of measuring instruments

2) Measuring instruments Measuring instruments include: 1 L88 optical brightness meter, 2 range finders, 1 tape, 1 second chronograph, 1 camera, 1 recording book and 1 private car (Fig. a). 3) Measuring principles Tab.3 Principles of field measurement

Measuring time

The days with fine weather, moderate humidity and good atmospheric visibility between February, 2014 and April, 2014 were selected as the measuring time. Each measurement began at 19:30.

Measuring sites

A LED panel can be seen as an area light source and the brightness level at the normal direction is the highest. Therefore, the measuring sites were selected where LED panels affect drivers‟ vision to the largest degree. Meanwhile, the sites were parallel to the stop line at road intersections (Fig. b).

Height of measuring vision

Try to simulate driving situations as much as possible during measuring. The height of measuring vision was set as 1.20m by referring to drivers‟ driving vision.

Dotting position

The dotting position of optical brightness meter is roughly set in the center of large LED panels during the measurement of large outdoor LEDs‟ optical property parameters.

Fig. b Schematic diagram of measuring sites selection

Fig. c Schematic diagram of background light measurement

Measuring duration

Measure each large LED panel at typical road intersections for 3 minutes. The time interval of recording large LED panels‟ brightness variations is 4 seconds.

Taking photos

Record of large outdoor LED panels‟ photos synchronizes with the record of brightness data. The time intervals are both 4 seconds/time and the length of recording photos is 3 minutes.

Use the L88 optical brightness meter for measurement. Select nine directions east-southeast-south-southwest-west-northwest-north-northeast-central above each Measuring measuring site. Measure three times in each direction and take the average. The background measuring height is 1.5m. Meanwhile, try to avoid the interferences of the light from brightness buildings and the scattered light from street lamps during measurement to obtain the sky brightness data of the typical sites (Fig. c).

几 Tab.3 Appendix III: Measurement table of typical LED panels’ transient brightness Time interval (s)

100

104

108

112

116

120

124

128

132

136

140

144

148

152

156

160

164

168

172

176

180

Brightness (xcd/㎡) Time interval (s) Brightness (xcd/㎡) Time interval (s) Brightness (xcd/㎡) Time interval (s) Brightness (xcd/㎡)

Site

Brightness mean

Brightness maximum

Brightness minimum

Range

Appendix IV: Measurement table of ambient light at typical intersections Measuring site

Intersection between Sanhao Street and Wenhua Road

Measuring direction

North

Northeast

East

Southeast

Ambient brightness values

South

Southwest

West

Northeast

Average brightness

BLR

Central