How Can Retroreflective Clothing Provide More Safety Through Visibility in a Semi-Dark Urban Environment? a Study Taking Plac

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MASTER’S THESIS How can retroreflective clothing BY VIOLA SCHMITZ provide more safety through visibility in a semi-dark urban Royal Institute of Technology environment? KTH School of Architecture Master’s Program in A study taking place in Scandinavia. Architectural Lighting Design 2018-2019

24.05.2019 AF270X VT19-1

Tutor: Foteini Kyriakidou

Index

Abstract P. 2

1. Introduction P. 2 2. Background P. 3 2.1. Urban Background P. 4 2.2. Biological background P. 4 2.2.1. Reflexes and reactions P. 4 2.2.2. Types of vision P. 4 2.2.3. Effect of pattern P. 5 recognition 2.2.4. Human field of vision P. 5 3. Analysis P. 6 3.1. Analysis: Retroreflectors P. 6 3.2. Analysis: Existing products P. 7 4. Methodology P. 9 5. Methods P. 10 5.1. Survey: P. 10 Lines defining the human body 5.2. Video Experiment: P. 10 Designs in motion 5.2.1. Analysis: Location P. 10 5.2.2. Video Experiment P. 11 5.2.3. Procedure P. 12 5.3. Experimental survey: P. 12 Size of a human 5.4. Visualization: P. 13 Pattern recognition in surroundings 6. Results P. 14 6.1. Survey: P. 14 Lines defining the human body 6.2. Video Experiment: P. 15 Designs in motion 6.2.1. Analysis: Location P. 15 6.2.2. Video Experiment P. 16 6.2.3. Observation P. 17 6.3. Experimental survey: P. 17 Size of a human 6.4. Visualization: Pattern P. 17 recognition in surroundings 7. Discussion P. 18 8. Design Proposal P. 19 9. Conclusion P. 20

Appendix P. 21 List of Figure P. 35 References P. 38

Abstract

Being inconspicuous in the dark outdoors can cause accidents including physical injuries. To prevent pedestrian being involved in accidents it is necessary to make them most visible to approaching people.

This Master’s Thesis examines the use of retroreflective clothing in a semi-dark urban environment to provide safety through conspicuity. Through analysing the lighting situation in Stockholm, the ability of the human vision, reactions and existing products it has led to experiments and surveys to find the most efficient line placement and pattern to make an individual recognizable as human on approach.

The results were that body outlines and horizontal lines along joints made a human most identifiable. Most conspicuity was given when lines were wider than 2cm and patterns contrasted to the surroundings.

As the experiment was conducted in a semi-dark setting, different retroreflective design solutions might be more adequate for other lighting scenarios with more or less light.

Keywords: Retroreflectors, High-visibility clothing, personal protective equipment (PPE), Safety

1. Introduction

Various national backgrounds affect people’s behaviour around daylight. Looking at Sweden, the days through winter get immensely shorter and darkness increases. With the increasing darkness, individuals start to wear more and more attachable retroreflectors to make themselves visible in the dark. Unfortunately, few commercial products provide full safety. Most retroreflectors, especially on athleticwear, are too small to make a person visible and they are often placed at positions facing one direction. How can a retroreflector placed in the back make you visible when a bike or car approaches you from the front? Even if it is luckily the right position, is the pattern accurate enough to reveal that you are an actual person? To see how to take the most advantage out of retroreflectors it is necessary to examine how the placement of retroreflectors, their shape, and size on clothes can not only give the feeling of being safe but also give more safety in the darkness. In order to do so, this study will firstly investigate retroreflective materials, existing products, and pattern recognition. Secondly, based on experiments, the work will answer which placements on a human body are most important to make a human visible and which designs help to make a person stand out from the surroundings. Thirdly, a design will be presented as a product(s) solution to the problem that aims to improve visibility based on the research and experiment outcome.

The focus of this study will be based on testing retroreflective clothing designs specifically on the situation of a biker meeting a pedestrian in a semi-dark urban space, since cycling counts to one of the most-used means.i

2. Background

2.1. Urban Background

Stockholm, Sweden is located with a 59° 20’N latitude and 18° 3’O longitude of the northern hemisphere. ii Approximately 1 million inhabitants iii have to deal with a long and dark winter and it’s difficulties. The minimum of daylight hours is at its peak on the 21st of December and contains 06:05h of daylight (Figure 1) iv.

Figure 1: 2019 Sun Graph for Stockholm

In addition, Stockholm is dealing with different light levels of a lot of contrast due to the mix of nature and the spatial areas. Assuming employed persons work in average from 9 till 16 o’clock, that would mean they most likely commute to work in civil or nautical twilight.

The most common public transportation in Stockholm is commuter trains, subways, boats, trams, buses, and bikes (Figure 2).v

Figure 2: Cycling routes in Stockholm: The common cycling route situations vary. Most likely Stockholm provides cycling lanes along the water or next to the street, which often leads through or along parks and ends up on car roads.

Therefore, a semi-dark environment can make it difficult to see people in the dark which can be dangerous for not only people who commute but also for bikers, pedestrian, walkers or runners in the outside environment.

2.2. Biological Background

Visibility in the dark can help to react on people and obstacles and help to prevent accidents. This has to take into account the facts of the adjustment of the human eye in a semi-dark or dark environment, pattern recognition, and reaction time.

2.2.1. Reflexes and reaction

The human body protects itself by reflexes and reactions. Reflexes are involuntary movements that can act on an impulse before that impulse reaches the brain, whilst reactions are movements caused by processing visual, acoustic or tangible information. A human reacts in average 0.25 seconds to a visual stimulus, 0.17 seconds to an audio stimulus, and 0.15 seconds to a touch stimulus. vivii

In a situation that two people in the dark react on each other, there will not be any reaction in terms of touch stimulus since they are on distance by the time they are supposed to react on each other. As most of the times headphones are used, it is also most likely that an individual reacts with the visual stimulus, which reacts with the slowest reaction time.

2.2.2. Types of vision

Therefore it is necessary to understand how the human eye adjusts in the dark to provide quickest reaction time.

The human eye focuses light to produce sharp images. There are three human visions which are photopic, mesopic, and scotopic vision. The scotopic vision works for very low light conditions and functions due to rod cells in the eye, which make objects visible, but they appear in black and white. The mesopic vision is made for low light conditions and combines the scotopic and the photopic vision. The photopic vision provides colour perception in well-lit conditions by using the eye’s cone cells. viii ix

The human eye can sense a factor of 1.000.000.000 different light signals, which can in a modification of light conditions rate down to a ratio of 1.000. It takes approximately 30 minutes that the human eye adapts from full sunlight conditions to complete darkness, while most of the adaption occurs in the first 5 minutes.x “Cone cells are able to regain maximum retinal sensitivity in 9-10 minutes of darkness whereas rods require 30-45minutes to do so.”xixii

Once the eye adapts to the darkness, the brain creates an image through shape identification or pattern recognition.

2.2.3. Effect of pattern recognition

The effect of pattern recognition is often seen in the appearance of animals which either adapt to their surroundings called camouflage (Figure 3) to hide or to scare enemies off which are often patterns similar to a strong and dangerous animal (Figure 4).

Figure 3: Camouflage: an almost invisible turtle

Figure 4: Venomous Coral Snake vs. Non-venomous king snake

In both cases, it is an adaption to the surroundings. Dame can vertical and horizontal lines look like a lamppost or railing in an urban environment. As soon as patterns are used, which are abstract to the surrounding, it will create a contrast and help the object become more visible.

2.2.4. Human field of vision

Most visibility is provided when an object is within the human field of vision, which is approximately 120° xiii

Figure 5: Human field of vision

3. Analysis

3.1. Analysis: Retroreflectors

Retroreflectors are materials with a surface that reflects light coming from any angle back to its source with a minimum of scattering. The first time used was 1937 to help drivers to see signs and to coordinate on asphalt roads. After 1980 the retroreflective materials made it on sneakers, backpacks, clothes, such as uniforms, and sports clothes to provide visibility in the dark. xiv xv The most commonly used retroreflectors are corner reflectors and cat-eye reflectors, which are most valuable as a safety device in road markings. xvi A corner reflector is consisting of three mutually perpendicular, intersecting flat surfaces, which reflect waves back directly towards the source (Figure 6). xvii

Figure 6: Corner reflector principle

Cat-eye reflectors are consisting of two pairs of reflective glass spheres set into a white rubber dome, mounted in a cast-iron housing (Figure 7 , Figure 8).xviii

Figure 7: Cat eye reflector as a bike reflector Figure 8: Cat eye reflector and its principle

Cat-eye reflectors are most useful in a foggy environment and are largely resistant to damage from snow. xix

According to the brand ‘brilliant’, reflectors on clothes factories most likely use retroreflectors (Figure 9) which reflects almost 100% of the light striking the material back to the source.xx

Figure 9: 2 principles of ‘brilliant’ reflectors.

3.2. Analysis: Existing Products

Retroreflective clothing and attachable

There is already a wide range of retroreflective attachable to help to make humans in the dark visible:

Figure 10: Reflective Lock Laces Figure 11: Nathan Strobe Light Figure 12: Reflective Safety Skin Color

Figure 13: Xinglet Figure 14: Reflective Ankle Bands Figure 15: Reflective Socks Figure 16: Reflective Pendant

Figure 17: Reflective Shoes: SSENSE x Figure 18: Nike – Reflective Jacket Figure 19: Nike – Reflective Reebok Run.r96 Joggers

Retroreflectors are most likely placed on clothes either on sports clothes or uniforms to provide visibility and with that feeling of safety.

The retroreflectors placed on most popular sports clothes are often small details, such as small, thin, single-placed lines (Figure 17,18,19).

These sports clothes are found at adidas and Nike which have their own category for reflective clothes on their website. Which means they are meant to have the use of providing visibility.

All these retroreflectors are made for casual use such as cycling, walking and dog walking.

In the workspace, there are different reflective safety clothes depending on the employment and their risk of injuries.

A fireman (Figure 20) and EMTs (Figure 21) for instance wears personal protection equipment (PPE), which includes retroreflective stripes as a basic defence against personal injury.xxi xxii

Figure 20: Firemans personal protective equipment (PPE) Figure 21: EMT wearing a reflective vest

Other professions such as policemen, construction site workers, road workers etc. are wearing retroreflective clothing for the same reasons.

The retroreflective surface of workspace equipment is by far bigger than retroreflectors used in a private casual pace.

4. Methodology

The presented analysis shows a wide range of existing retroreflective designs. Even if these products are advertised to provide visibility, own experiments were needed to show if these existing designs and own new designs are efficient and how they could be improved. The experiments could be tested in varieties of collisions of either pedestrian approaching pedestrian/joggers, bikers or cars. Not only varieties of objects qualify for the experiment, but also location, time of the day and reaction time could have a big impact.

The efficiency of the existing products depends on the perception of random people, therefore, to get most accurate results, the designs had to be uploaded to an online survey to be rated by these random people. How the designs are not only visible enough in freeze frame, it was decided to make the next experiment with a pedestrian or jogger meeting a biker in a park in a semi-dark environment. This shows if the biker would have enough time to react to the approaching person or not. The main light source is hence from the bicycle and could also expose where in Stockholm is already enough light to make an individual visible or not around a time when most people commute. To get a better overview of the light situation in the park, the lux-levels of the park had to be measured with a lux meter.

5. Methods

5.1. Survey: Lines defining the human body

To secure most safety in the dark through visibility, pedestrian have to be identified as humans to ensure that observers can react with quickest and most accurate movements.

The first survey aims to find the design which reveals a human by the most efficient retroreflector- line-placement on a human body.

To test which designs can reveal a human body, 15 retroreflective designs were created based on the product research of commercial brands for private use, safety equipment and based on lines placed in proportion to the anatomical background of a human. All 15 designs were in a 2D frontal view, shown in highest contrast of a black background to only make the retroreflective design visible. All designs were uploaded to an online survey where participants, regardless their age, gender or cultural background, could rate in a scale from 1 to 10 (1 not identifiable, 10 easy identifiable) how easily a human was identifiable by only the line placement.

5.2. Video Experiment: Designs in motion

However, it is necessary to see if the previously mentioned retroreflective designs are present enough to be visible in reality and help to identify a human when being in motion or on the other hand, to see where are lacks in the urban lighting that retroreflective clothes are even necessary.

5.2.1. Analysis: Location

To test these aspects, it was essential to analyse one of the biggest parks used as crossing path in Stockholm. Rålambshovsparken (Figure 22) is located west of Stockholm’s city centre and is therefore surrounded by commuters, such as pedestrian and bikers. The park provides light levels (Figure 23) from full darkness to fully lit-up spaces, which contributes to a wide range of adequate results of testing retroreflectors in different lit-up environments.

Figure 22: Location of Rålambshovsparken

Figure 23: Pictures of the Park

To see how evenly the park is lit up, an illuminance map was created, measured with a lux meter on the 5th of April 2019 after 21:30 o’clock which means the light levels got measured in between an astronomical twilight up till a night atmosphere which is equal to the Swedish winter daylight on a peak day of 21st of December between 16:39 till 6:52 o’clock (Figure 1). A satellite map also visualizes the surroundings to show which obstacles created shadows and which materials might reflect light already.

5.2.2. Video Experiment: Designs in motion

To see how the retroreflective designs work in reality and to see if the factor of ‘motion’ can change the perception of identifying a human body, it was necessary to test them in a 3D scale in the above mentioned location. Out of all designs of the first survey, 4 designs were chosen to be tested in motion: the least, the average, the easiest identifiable design and one construction site design. The lines width of the designs were between 1,5 and 4 cm.

A runner, wearing those different retroreflectors, approaches from 4 different directions running towards a biker (Figure 24).

Figure 24: Tested running routes

Each situation with each design was filmed with a camera in an average height of 135cm, which is approximately the height of a biker’s vision. To have the same light requirements, there was a bike lamp with 300lumen attached below the camera in an average bike lamp height of 110cm (Figure 25).

Figure 25: Experiment set-up

5.2.3. Procedure

All 16 videos were recorded with clear sky conditions on the 4th of April 2019 between 21:30 and 22:30 o’clock. The videos were uploaded in an online survey, where the participants had to say at which second they saw motion and at what time they could identify it as a person and if it was cause of the retroreflectors. To know in which scale they were watching the videos, the survey ended with the final question which device they watched the videos with.

The distances of the running routes were measured in advance to understand how far in distance the runner was identified.

To not influence the results by a specific pattern, the videos were played in a random order, so the observers see the runner always approaching from different directions and in different light levels.

5.3. Experimental survey: Size of a human

Essential is to know how far a person is in distance to react on it in the quickest way.

When the highest and the lowest part of the human body is visible, it is understandable how tall and maybe how far a person is in distance. But what if the lines are missing which define the highest and lowest part of a human or lines are placed unproportionally to the human anatomy?

To see how easy people can understand the proportions of a human body, two 2D-retroreflective designs were uploaded on an online survey where participants had to guess how tall a person (Figure 26) is just by seeing the retroreflectors. This action helps to understand which parts of the body are most important to highlight to find an optimal retroreflective line placement.

Figure 26: Example design of 2nd survey

5.4. Visualization: Pattern recognition in surroundings

Based on the research of the effects of pattern recognition of animals, it is necessary to understand the visual view of contrasting surroundings in the dark and which patterns are even quickest recognisable in contrast to the surroundings. Urban elements which are lit up in the dark or get highlighted by their material reflections, are often linear objects such as railings and lampposts. As a test which lines or designs are in contrast to the surrounding background and is therefore easy visible, there were 4 pictures created showing vertical and horizontal lines on a black background symbolizing lit up railings and lamppost in night time. A randomly retroreflective line design was placed in the picture to see which one of them really stands out in between their surroundings:

Figure 27: Pattern recognition in surroundings

6. Results

6.1. Survey: Lines defining the human body

58 participants rated 15 designs from a scale from 1 to 10 (1 not identifiable, 10 easy identifiable) how easy a human was identifiable by only the line placement (Appendix A).

Design detail Hard identifiable (1-3) Identifiable (4-7) Easy identifiable (8-10) Human body outline 1,02% 17,16% 81,82% No highlights at body centre 72,4% 27% 0,6% Small detail retroreflectors 79,3% 19,85% 0,85%

The human body was rated as easyily identifiable, as soon as…

… the human body had an outline. … lines were thicker. … horizontal lines along the joints were added. … small parts of the shoulder, arms and legs were pointed out. … the design had evenly spread horizontal and vertical lines without add-ons.

The human body was rated as not identifiable, as soon as…

… the centre of the body was not highlighted. … the dimensions were not clear e.g. when horizontal lines were unproportionally or not placed along the joints.

One of the easiest identified designs (Appendix A) was Design 1 (Figure 28), which has the combination of horizontal lines along the joints and an outline of the human body with 2cm wide stripes. Design 2 (Figure 29) was in the average of identifiability, working with stick figure design, showing the full length of the body with 2cm wide stripes. One of the least easy identifiable design was Design 3 (Figure 30) which only had small reflective details with 1,5cm wide lines, without showing the full length of the body nor making visible where the joints are placed. Design 4 (Figure 31) had 4cm wide lines and shows the typical construction site design, which got average rated.

Figure 28: Design 1 Figure 29: Design 2 Figure 30: Design 3 Figure 31: Design 4

6.2. Video Experiment: Designs in motion

6.2.1. Analysis: Location

In Figure 32 it shows clearly that on one half of the park are high trees planted which produce a lot of shadows and block light which raises the contrast of light level in the park. Reflections on the water do not light up the park, but it provides visibility to see the edge of the waterfront.

Figure 32: Satellite View of Rålambshovsparken Figure 33: Illuminance Map of Rålambshovsparken

The illuminance map in Figure 33 reveals the different light intensities and 3 colour temperatures in the park. Focusing on both maps at the same time, the maps suggest that lampposts are mostly placed along paths where trees are planted. Light almost does not reach the centre of the park according to the measurements of the lux meter.

In the survey of the video experiment, 23 participants responded to the answer if they could identify the runner due to the presence retroreflectors (Appendix B.2).

location

Pedestrian was 26% 39% 58,75% 42,5% visible by existing light sources Pedestrian was 74% 61% 41,25% 57,5% visible only through retroreflectors

Only in one of the locations, it was a well-enough lit up space that more than 50% of the observers saw the person approaching just by the already existing light sources. That means that either the existing light sources are not producing enough light to make a runner quick enough visible or, that the existing light sources were not placed well enough that the retroreflectors got activated.

6.2.2. Video Experiment: Designs in motion

In terms of putting the 2D-designs in a 3D-scale, all of the retroreflectors helped to make the runner visible. 23 participants answered the online survey and gave responses to how quick they saw motion and when they could identify that the motion comes from a human (Appendix B.1).

Built upon the first survey was not only Design 1 (Figure 28) the one being easiest identifiable as a human, it also provided the quickest reaction time of the 4 tested designs in the Video Experiment. The second quickest reaction time showed Design 2 (Figure 29) and Design 4 (Figure 31), whilst Design 4 is using more retroreflective surface than Design 2. Through the small retroreflective surfaces of Design 3 (Figure 30) it was difficult for participants to identify the approaching runner quickly, which was leading to the result of the slowest reaction time of all 4 tested designs.

Figure 34: Example: Video experiment reaction time on motion (blue) and human recognition (green)

Participants watched the videos in 52% of the cases with Computer and in 48% of the cases on their smartphone (Appendix B.2) which means, they had a much smaller scale to see the retroreflective designs in motion than in a real-life situation. Nevertheless, the quickest reaction time was shown in the first location (Figure 34), with Design 1 (Figure _28) when observers reacted after 3:14sec on motion, which is in distance of 26 meters to the camera or the symbolic biker.

6.2.3. Observation: Video Experiment - Designs in motion

The movement was more visible when the retroreflectors were placed along the joints. As soon the feet were not lit up it was hard to know how tall the approaching person is and resulting not knowing how far in distance the person is moving.

As soon as the runner approached very narrow from the sides, the retroreflectors did not get activated, as a result of the light source below the camera was not reaching with its angle towards the retroreflector.

6.3. Experimental survey: Size of a human

Figure 35: Size of a human – design 1 Figure 36: Size of a human – design 2

A B C D E Design 1 9% 4% 26% 48% 13% Design 2 4% 18% 44% 30% 4%

Table 1: Results - Size of a human designs

Regarding how important proportions of line placements are, the study shows the experimental survey ‘Size of a human’. As seen in Figure 35 and Figure 36 the correct length of the body is along line E. In Table _ it shows clearly though that only 13% (3 out of 23) of participants for Design 1 and 4% (1 out of 23) of participants for Design 2 were able to guess the right size of the body by just seeing the retroreflective design.

6.4. Visualization: Pattern recognition in surroundings

The pictures above (Figure 27) show clearly that as long as patterns are similar to the surroundings, it is hard to see them quickly. As more abstract the pattern is to the surroundings as more it stands in contrast to it.

7. Discussion

The present study shows the value of retroreflectors to make pedestrian more conspicuous at night in Stockholm, Sweden. The findings noted that pedestrian have to be identified as humans to ensure that observers can act with quickest and most accurate reactions.

The results of the placement of the design on clothing show that a human body is easiest identifiable when the outline of the human body is visible, when horizontal lines go all the way around the body, when the designs are placed along the joints and when the highest and lowest part of the body is visible.

This conclusion directly leads to the aspect that a design has to be proportional to the human anatomy. As soon as lines are not placed on the joints but a few centimetres higher, observers have trouble knowing the person’s height; therefore the information is missing on the distance of the person, which can lead to inaccurate reaction time and its consequences. The experimental survey, asking for the size of a human just by seeing the design, revealed that almost no person guessed the correct size. Participants were used to designs based on proportions of the human body, which gave them the illusion of a much smaller person since the lines were higher placed than the joints in reality.

In the video experiment, designs were tested in motion which added the idea that retroreflectors are easier visible as bigger they get. Retroreflective stripes with 2cm width seemed to be big enough to provide visibility.

The video experiment was also showing that the bicycle light source has not a wide enough angle to reach to the sides of the bicycle, which often made the retroreflectors not activated when the runner approached from the side. This means that either bicycle lamps should have a wider range they can lit up by e.g. placing an additional light source facing sideways or that the urban lighting has to be improved to make pedestrian, in general, more visible.

This idea leads to the question of how the designs could be applicable in other cities in different latitudes. The design principles of how a human body is easiest identifiable would still be the same, but depending on how much light in the surroundings is given, maybe fewer retroreflectors would be needed.

When the design blends in with its surroundings, it becomes more challenging to provide visibility; thus, contrast must be provided. This notion suggests that by using designs with horizontal and vertical lines, it is harder to see in surroundings of lampposts and railings, while using e.g. dots, crosses or wave designs would give a high contrast to be more visible. This means the designs would need to be adapted to every situation. If a wave design would be used close to the water, the contrast of the design and the surrounding would be maybe not high enough to make the person visible.

Also if everyone in the same area would wear clothes with the same design, they would build a new surrounding with their clothes, which means the contrast from each design would probably not be high enough to make one specific person visible. That means that there should be several different designs to make each person visible enough. This could be another investigation of how many same designs are actually good to use to still provide safety through visibility.

8. Design Proposal

The design principles visualized:

Figure 37: outlines Figure 38: vertical Figure 39: highlight Figure 40: pattern contrasted to surroundings Lines along joints The top and bottom

Also 2cm thickness of lines enhance conspicuity. The following examples for design solutions were created:

Figure 41: optimum design Figure 42: modified design in general surroundings in general surroundings

9. Conclusion

This study examined how retroreflective clothing can provide more safety through conspicuousness in a semi-dark urban environment.

Sweden is dealing with an increasing lack of daylight while winter season. This lack causes a deficiency of safety through inconspicuousness in the darkness to the many pedestrian and bikers commuting through Stockholm. Visibility in the dark is only provided by the adjustment of the human eye which can adapt to the specific light level by recognizing contrast. This is significant when two individuals approach each other to enhance their reaction time and movement.

Products based on retroreflectivity can assist to reveal an individual in the dark. As analysed, most of the products for private use are not reaching their highest efficiency due to too small sized designs, wrong placements or too neutral patterns. Safety equipment gives a hint of how retroreflective lines have to be placed to make a human visible.

Based on the researches and experiments, the most important design principles were extracted, which help to make an individual conspicuous: outlines of the human body, horizontal lines along the joints, highest and lowest part of the body being highlighted, lines wider than 2cm and patterns contrasted to the surroundings.

The next step to take the study further would be firstly how not only retroreflective clothes but also how retroreflective attachables could be improved to provide visibility in the dark. Secondly how the retroreflective clothing would behave in a different spatial space e.g. along a well-driven road. Thirdly how the retroreflective clothes would need to be changed due to different seasons and last if the person is also visible enough for car drivers to provide quickest enough reaction time to prevent accidents.

Appendix

Appendix A:

Appendix B.1:

Appendix B.2:

List of Figures

Figure 1: 2019 Sun Graph for Stockholm https://www.timeanddate.com/sun/sweden/stockholm , 23.05.2019

Figure 2: Cycling routes in Stockholm https://www.slowtravelstockholm.com/resources-practicalities/biking-in-stockholm/ , 23.05.2019

Figure 3: Camouflage: an almost invisible turtle Own representation bv Viola Schmitz

Figure 4: Venomous Coral Snake vs. Non-venomous king snake https://study.com/academy/lesson/batesian-mimicry-examples-definition-quiz.html , 10.05.2019

Figure 5: Human field of vision https://www.mensenjoy.com/visione-periferica-uomini/ , 10.05.2019

Figure 6: Corner reflector principle https://uk.m.wikipedia.org/wiki/%D0%A4%D0%B0%D0%B9%D0%BB:Corner_reflector.svg , 04.05.2019

Figure 7: Cat eye reflector as a bike reflector C.T. Kiss, M. Kumagai, D. K. Tinsworth etc. , ‘BICYCLE REFLECTOR PROJECT’, P.6

Figure 8: Cat eye reflector and its principle C.T. Kiss, M. Kumagai, D. K. Tinsworth etc. , ‘BICYCLE REFLECTOR PROJECT’, P.4

Figure 9: 2 principles of ‘brilliant’ reflectors. https://brilliantreflective.com/what-is-reflective-material/ , 02.05.2019

Figure 10: Reflective Lock Laces https://www.amazon.com/LOCK-LACES-Reflective-Elastic-Shoelaces/dp/B00OJLNKAI , 02.05.2019

Figure 11: Nathan Strobe Light https://bayrunningshop.co.uk/products/nathan-strobe-light , 02.05.2019

Figure 12: Reflective Safety Skin Color https://www.columbusrunning.com/products/reflective-skin-reflective-skin , 02.05.2019

Figure 13: Xinglet http://www.amphipod.com/products/visibility/reflective-vests/xinglet , 02.05.2019

Figure 14: Reflective Ankle Bands https://www.ginifab.com/custom_bracelets/reflective_ankle_bands.html , 02.05.2019

Figure 15: Reflective Socks https://www.iamlocale.com/socks/one-inch-reflective-band-socks , 02.05.2019

Figure 16: Reflective Pendant https://www.dhgate.com/product/ornament-bag-reflective-pendant-bag- pendant/414583241.html , 02.05.2019

Figure 17: Reflective Shoes: SSENSE x Reebok Run.r96 https://sneakernews.com/2018/06/21/ssense-reebok-runr-96/ , 02.05.2019

Figure 18: Nike – Reflective Jacket https://www.nike.com/de/t/veste-de-running-shield-pour-7BTDpBzN/855643-010 , 02.05.2019

Figure 19: Nike – Reflective Joggers https://www.nike.com/de/t/shield-phenom-herren-laufhose-rT2gnm/AJ6711- 010?nst=0&cp=euns_kw_pla!fr!goo!cssproducts!c!!!302634061104&gclid=CjwKCAjw5pPn BRBJEiwAULZKvj8KXxsckzRQ3w9ys7TMt_TP5FPVN4Wk7tz5CANG6YI0oTS5mWa2fhoC18EQAvD_BwE &gclsrc=aw.ds , 02.05.2019

Figure 20: Firemans personal protective equipment (PPE) Mark C. Henry & Edward R. Stapleton, ‘EMT Prehospital Care’, Jones & Bartlett Learning, Burlington, 2012, 4th edition edited by Dennis C. Edgerly, p.40

Figure 21: EMT wearing a reflective vest

Mark C. Henry & Edward R. Stapleton, ‘EMT Prehospital Care’, Jones & Bartlett Learning, Burlington, 2012, 4th edition edited by Dennis C. Edgerly, p.40

Figure 22: Location of Rålambshovsparken https://www.google.com/maps/place/Stockholm,+Schweden/data=!4m2!3m1!1s0x465f763 119640bcb:0xa80d27d3679d7766?sa=X&ved=2ahUKEwiX4bnNnrDiAhWDD2MBHff3AK8Q8gEwAHoE CAoQAQ , 23.05.2019

Figure 23: Pictures of the Park Own representation bv Viola Schmitz

Figure 24: Tested running routes Own representation bv Viola Schmitz

Figure 25: Experiment set-up Own representation bv Viola Schmitz

Figure 26: Example design of 2nd survey Own representation bv Viola Schmitz

Figure 27: Pattern recognition in surroundings Own representation bv Viola Schmitz

Figure 28: Design 1 Own representation bv Viola Schmitz

Figure 29: Design 2 Own representation bv Viola Schmitz

Figure 30: Design 3 Own representation bv Viola Schmitz

Figure 31: Design 4 Own representation bv Viola Schmitz

Figure 32: Satellite View of Rålambshovsparken https://www.google.com/maps/place/Stockholm,+Schweden/data=!4m2!3m1!1s0x465f763119640bc b:0xa80d27d3679d7766?sa=X&ved=2ahUKEwiX4bnNnrDiAhWDD2MBHff3AK8Q8gEwAHoECAoQAQ , 23.05.2019

Figure 33: Illuminance Map of Rålambshovsparken Own representation bv Viola Schmitz

Figure 34: Example: Video experiment reaction time on motion (blue) and human recognition (green) Own representation bv Viola Schmitz

Figure 35: Size of a human – design 1 Own representation bv Viola Schmitz

Figure 36: Size of a human – design 2 Own representation bv Viola Schmitz

Figure 37: outlines Own representation bv Viola Schmitz

Figure 38: vertical lines along joints Own representation bv Viola Schmitz

Figure 39: highlight the top and bottom Own representation bv Viola Schmitz

Figure 40: pattern contrasted to surroundings Own representation bv Viola Schmitz

Figure 41: optimum design in general surroundings Own representation bv Viola Schmitz

Figure 42: modified design in general surroundings Own representation bv Viola Schmitz

Appendix: Own representations bv Viola Schmitz

Tabel 1: Own representations bv Viola Schmitz

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