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

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How Can Retroreflective Clothing Provide More Safety Through Visibility in a Semi-Dark Urban Environment? a Study Taking Plac 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 0 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 1 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 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. 3 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. 4 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 5 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).
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