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Image credit: Mike Knell 959 words / 4-minute read When you hear the term "light pollution", what comes to mind? While it's actually a broad term encompassing effects both on the ground and in the night sky, most people think of it as the inability to see the stars at night. That effect in particular, called "skyglow", results from light emitted on the ground up toward the sky. That light scatters in the atmosphere, which redirects it back toward the ground. There it competes with starlight and causes the sky to look grayish and washed out. Thanks to research described in a new paper in the journal Science, we know that skyglow is increasing around the world at a stunning rate. The study, published in January, found the rate of increase is about ten percent per year when averaged around the world. Counting stars instead of lightsResearchers in Germany analyzed tens of thousands of observations made by citizen-scientists between 2011 and 2022 as part of the "Globe At Night" project. The organizers ask participants to first locate familiar constellations in the night sky. They present maps of those constellations showing differing numbers of stars to show varying degrees of skyglow. The participants decide among the charts which best matches their own local night skies. This provides robust estimates of night sky brightness that scientists can compare against other sources of data about light pollution. Globe At Night charts for the constellation Orion. To estimate the brightness of the night sky, participants compare these charts to the night sky from their locations and find the best match. The new work is the first large-scale analysis of the Globe At Night estimates. Until now, Earth-orbiting satellites provided the only global view of light pollution. Earlier studies involving satellite images concluded that light pollution on the ground grew at a much slower pace. A 2017 study concluded that the rate was around two percent per year in the first half of the last decade. Satellites flying blindThe new estimate in Science looks up from the ground instead of down from space, which may explain some of the difference. The satellites used to gather the night-lights data don't see blue light at all. They were not designed to make light pollution measurements in particular, so their onboard sensors aren't ideal for the job. Their insensitivity to blue light is a problem given how the color of light at night continues to change. Since around 2010, many cities across the world converted their stock of public lighting to new, white light-emitting diode (LED) technology. They did this in hopes of realizing major reductions in energy use and financial cost with these energy-efficient light sources. But white LED emits a lot more blue light than earlier lighting technologies. Satellites thus tend to under-count the amount of light at night they receive in space. That same blue light also scatters more strongly in the atmosphere than other colors. All other factors being equal, that effect explains in part why nights are getting brighter. A global composite view of the Earth at night in the year 2015 made from artificially colored orbital satellite data. The relative 'blindness' of satellites to blue light means images like this underrepresent the true extent of night lights on our planet. Image courtesy of NOAA/NASA. Besides to the color issue, satellites also miss some of the light directed upward from the ground because it becomes skyglow. Since they are above the atmosphere, satellites only detect light rays that reach them. Some of those rays never make it because they're redirected back down to the ground. So while ground-based observers saw their night skies brighten in the past decade, satellites recorded a much slower rate of change. Furthermore, some light sources emit in ways that makes it unlikely their light will be seen directly in space. Sources like lit windows of buildings and illuminated signs emit light toward the horizon. Those sources are among the most important contributors to skyglow, but very little light they emit gets to the satellites. And there is evidence that at certain hours of the night, those sources dominate light escaping from cities. Visual observers on the ground sense at least some of the "missing" light that satellites don't see. That way of estimating the brightness of the night accounts for both the increase in light emissions and a trend toward bluer sources. Citizen-scientists also extend the reach of light pollution studies. It's often easier to recruit them to count stars where they live than place light sensors in the field. That is especially true in very remote locations around the globe. Citizen science for global changeBut even considering that volunteers provided about 50,000 measurements in the preceding decade, the information is incomplete. Vast swathes of land contained no observers at all. That left scientists to make informed guesses in places like Africa, where satellites suggest night lights are increasing the fastest.
Although the study authors note that known methods of reducing light pollution yield reliable results, current initiatives aren't producing results. This concerns light pollution researchers and activists alike. Skyglow is one symptom of a larger problem involving overuse of artificial light at night. We know it has negative impacts on everything from wildlife to energy use, traffic safety, and more. It's about much more than whether we can see the stars at night. As more people realize the seriousness of the issue, governments are taking note. Countries like Mexico have recently classified light pollution as a form of environmental pollution. This can bring the mechanisms of existing environmental laws to bear on the problem. The failure to reduce light pollution has real and lasting effects on communities. Wasted outdoor light at night involves measurable social and financial costs. Yet the new study authors admit that these messages about light pollution might heard by governments if the data were better geographically distributed. More people participating in Globe at Night would improve the reliability of the results. If the number of participants increased by a factor of 10, we would begin to see trends on scales smaller than whole continents. As lead author Christopher Kyba said, "If we could do that, we would surely find places that are doing better than average, and we could try to figure out what they are doing right."
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Image credit: NPS / Will Pedro 753 words / 3-minute read In January 2022 we wrote here about 'astrotourism', a kind of night-sky themed ecotourism, was "on the rise". The intervening year has seen this industry grow by leaps and bounds around the world. As the COVID-19 pandemic fades, people are hungry to see the world again and experience new adventures. For many who have never seen a starry night sky, an astrotourism experience fits the bill. There are a few places in the world where this mode of tourism is already well developed. For example, the Mackenzie region of New Zealand has a thriving local astrotourism industry. Many places have the right mix of dark night skies and daytime allure, but few have achieved such success. Those that do stand to gain much in the way of economic development, particularly in rural and economically depressed areas. The U.S. state of Utah is one of the exceptions. While famous as a winter playground for the "greatest snow on earth", tourists now flock to the Beehive State for other reasons. According to the Utah Office of Tourism, dark skies now have a higher public and media uptake than skiing. The magic of dark night skies above, with the celebrated beauty of the Utah landscapes and its vast public lands below, is a strong visitor enticement. That is especially true for families with children who have never experienced the splendor of the stars. In a sense, the modern idea of astronomy-themed tourism started in this part of the world. In 1969, formal stargazing programs were first offered to the public at Bryce Canyon National Park. As word of the region's night skies spread, early efforts to commercialize the experience took root. Opportunities available to Utah astrotourists now run the gamut from guided, small-group stargazing to astronomy-themed river running and 'glamping' experiences. While its full economic value to the state has yet to be quantified, there are reasons to think that Utah is already benefitting. One study, published in 2019, predicted that astrotourism will account for $6 billion worth of economic activity in the region during the 2020s. The surge in post-pandemic tourism means that number is probably on the low side of what's possible. Utah ranks number one with more accredited International Dark Sky Places than any other state or province in the world. Its dry climate and often favorable weather yield some of the finest night skies in the developed world. Travelers come to Utah from heavily light polluted places such as the East and West U.S. coasts, Europe and Asia to experience this firsthand. The government of Utah has taken notice, and it has begun to incorporate dark skies into the state's branding. For example, the Utah Governor has declared April as Utah Dark Sky Month for the past two years. And beginning in 2023 the state will offer a themed license plate to motorists. When seen during their travels to other states, it serves as an advertisement attracting more tourism. An early design concept for the Utah dark-sky specialty license plate, making its debut in 2023. Officials have come to recognize astrotourism as one of the most profitable sectors in the ecotourism industry. While famous for its "Mighty 5" U.S. National Parks set among the stunning scenery of southern Utah, daytime-only visits have a milder economic impact. Realizing that "half the park is after dark", astrotourism activities in and near the Mighty 5 offer further recreation opportunities to visitors. This not only adds significant value to visitor experiences, but it means more revenue for tourism operators and local governments alike. Even one night spent stargazing adds an overnight stay and two meals to a visitor's tab. This represents a highly profitable proposition.
The state's Office of Tourism developed a well-considered dark sky toolkit, debuting in 2022. One segment of that toolkit, "An Industry Guide To Astrotourism," offers a particularly powerful set of guidance and resources. As the field becomes increasingly professionalized, this level of state support helps bring new operators into the industry. It also grows a local knowledge base that can help with the development of new tourism products. Utah has become a best-practice model for the economic development possibilities of astrotourism. It provides clear, actionable information to interested communities and their affiliated DMOs (Destination Marketing Organizations). To this it adds branded marketing elements that reinforce a strong connection between Utah outdoor recreation and night skies. The result is a recipe for success to which people in other parts of the world now look as an example to guide their own local efforts. Dark-sky tourism now has a bright future, and Utah leads the way.
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Understanding the Bortle Scale12/1/2022 Image credit: Dark Sky Consulting 854 words / 3-minute read The brightness of the night sky at a given location is an important indicator of the health of the nighttime environment. Many factors influence what we see when we look up at night, as we recently wrote about here. Light pollution is only one factor to consider, albeit an important one. Rather than thinking only about brightness, sometimes one hears about night sky "quality". While the ways we characterize the the night sky can be rather technical, we wish for something simple. A convenient shorthand, first described two decades ago, offers such an approach: the Bortle Scale. Devised by amateur John Bortle, the scale is a simple and intuitive way to classify night sky quality. Everyone is familiar with scales that rank this or that over a range of, say, one to ten. The Bortle Scale ranges from one to nine, and it works backward: a better night sky gets a smaller number. The value of sky quality estimates Taking a small step back, why do we care about any of this? Quantitative measurements of sky quality are best, but data are often difficult to get. But it's much easier to get more people out in the field who can make subjective assessments. In turn, researchers can keep tabs on how conditions are changing in different places due to light pollution. We can also use this information to assess how well lighting retrofits are going, or to identify potential new astrotourism sites. But the question of "how dark is the night sky" is more complex than it seems on the surface. Besides artificial skyglow, there are many natural sources of light in the night sky. The contributions of these sources span a large range in brightness, and they vary in time; no two nights at the same location are ever the same. Other means of assessing night sky brightness are often not very consistent, making comparisons difficult. This also complicates quantitative measurements, so we end up relying on long-term statistical distributions that characterize the probability of any particular night having any particular sky quality. A simple approach That's where the Bortle Scale comes in. It aims to reduce some of the complexity of quantitative measurements while retaining the value of simple comparisons between sites. The scale divides night sky quality into nine levels ranging from badly light-polluted city skies to pristine rural skies:
For each level, it lists several distinguishing characteristics that users can look for. With some practice, users can tell the different levels apart with reliability. Because the Bortle Scale levels roughly overlap ranges of other sky quality indicators, it can be predictive. For example, the website lightpollutionmap.info provides an estimate of the Bortle Scale for any location with a click of the mouse. The instance below shows an area on the western outskirts of London, U.K., is a "Bortle 5" site. The Bortle level serve as a first guess of what quantitative measures of sky brightness might show. Of course, the Bortle Scale approach has its own drawbacks. It involves a subjective assessment specific to a particular observer. In that sense, it is "impressionistic" and depends on the conditions of a particular night. It's also sensitive to an observer's experience and visual acuity. The boundaries between the Bortle levels are often "fuzzy", calling for further shades of difference that the system doesn't permit. Yet with further impressions by other observers, the picture can become clearer. A study of citizen science data collected as part of the Globe At Night project supports this idea. Researchers compared thousands of visual night sky brightness estimates to satellite measurements and found good correspondence. They found that visual impressions "depend strongly on artificial skyglow and could be used to track lighting changes worldwide." Power in numbers Despite its limitations, Bortle Scale estimates have distinct value. Over time, variations among observers will even out and a 'typical' sky quality at a site emerges. The numbers can suggest places worthy of more study, and especially of quantitative measurements. Repeated site visits may suggest slow changes in sky quality over time, for better or worse. In particular, the first notion of degrading night skies may be a slide in the Bortle level.
And the Bortle Scale represents a comfortable language for use in talking to the public and elected officials. It can help support dark-sky conservation efforts by making the subject easier to understand. A straightforward rating can even impart a sense of familiarity to those who otherwise know little about light pollution. What is the Bortle Scale number for your location? You can look for it on lightpollutionmap.info, or try making your own estimate using John Bortle's original description. What you discover in the process might surprise you! Need help interpreting your results? Or maybe you want to take the next step and make more rigorous measurements of your site quality? Contact us today for advice.
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Image credit: M. O'Neill / NPS 766 words / 3-minute read Many people are feeling stressed out these days. In the wake of the COVID-19 pandemic and with major economic and political uncertainties ahead, it's understandable that so many people experience anxiety. The frenetic pace of life enabled by technology disconnects us from our roots in nature. As professionals debate the reality of 'nature deficit disorder', an increasing number of people look for solace in the natural world. Can access to a clear, dark night sky, and the awe it inspires, actually make us feel happier? The psychology of wonderAs a practicing psychotherapist, Ada Blair found herself asking that very question a few years ago. "I have a longstanding interest in how encounters with nature, including the sky, may positively impact wellbeing and even lead to transformation," she says. Having spent time on Sark, a small island in the English Channel that became an International Dark Sky Community in 2011, she experienced it firsthand. She wondered if the effect would stand up to scientific investigation. Blair found that the dark nights on Sark, which has almost no electric lighting, led residents to "a widespread belief that observing the night sky results in positive (and sometimes transformative) feelings." Her interviews with islanders revealed an internalized idea that their sense of wellbeing was in part supported by ready access to a dark night sky. Even before Blair began her investigation, there was evidence that exposure to artificial light at night influenced mental health. Higher levels of light at night correlate with a variety of disorders, [1,2] ranging from insomnia to depression. That in turn suggests that access to nighttime darkness is just as important to maintain good health. But could exposure to cosmic light also influence our sense of wellbeing? Conquering fear (of the dark)We don't yet have a lot of scientific evidence to establish a strong relationship between dark skies and happiness. But Dajana Bjelajac, of the University of Novi Sad, Serbia, and her co-authors see signs of a deep connection. "The relationship between humans and natural darkness has always been a dreadful one," they write. "People would admire the heavens, but at the same time, as diurnal beings, we have been and still are relentlessly searching for the best method to tame the night and bring the light into it." [3] Darkness can be terrifying for some people, although the source of that fear may have to do with a sense of vulnerability. Fear of darkness may equate to a fear of being unable to escape perceived danger. [4,5] If people sense that they are in safe spaces at night, their anxiety can ease and they are then able to enjoy the night sky. The effect of living in light polluted places like cities might influence this: when people fear for their safety in cities, they can transfer that fear to rural places. A safe space to be happyAstrotourism can create safe outdoor spaces at night for participants to shed some of that fear and enjoy the wonder of the night sky. It brings people closer to nature, which can further ease fear and promote feelings of safety. Given the lockdowns of the past few years, people are ready get back out into the world and experience new and varied forms of tourism. Some experiences, like dark night skies, may even help heal some of the trauma many have felt. In protected places accessible to the public, like certified International Dark Sky Places, people can find the sense of security they need to have such experiences. It can be something they share with friends and family, much as people thousands of years ago did when dark night skies loomed larger in human culture than they do today. Even fleeting glimpses of starry skies may be meaningful. Recent research results suggest that quality of nature experiences, rather than their frequency or duration, is more reliably predictive of mental health and wellbeing outcomes. [6] In "The Value of the Night Sky", economist Terrell Gallaway writes of the different ways we can look at natural nighttime darkness as a natural and economic resource. "The night sky is a superlatively wondrous and deeply threatened natural asset," he writes. "As an asset, the night sky is extraordinary in many ways beyond its obvious beauty and grandeur." The senses of wonder and awe that the night sky evoke might be the tonic that a weary world needs in troubled times. Whether it's conservation planning, field surveys or lighting policy formulation, we can help your achieve your goals in protecting the night. Contact us today to find out more. References[1] Yu, Z., Hu, N., Du, Y., Wang, H., Pu, L., Zhang, X., Pan, D., He, X., & Li, J. (2022). Association of outdoor artificial light at night with mental health among China adults: a prospective ecology study. Environmental Science and Pollution Research (Vol. 29, Issue 54, pp. 82286–82296). https://doi.org/10.1007/s11356-022-21587-y
[2] Tancredi, S., Urbano, T., Vinceti, M., & Filippini, T. (2022). Artificial light at night and risk of mental disorders: A systematic review. Science of The Total Environment (Vol. 833, p. 155185). https://doi.org/10.1016/j.scitotenv.2022.155185 [3] Bjelajac, D., Đerčan, B., & Kovačić, S. (2020). Dark skies and dark screens as a precondition for astronomy tourism and general well-being. Information Technology & Tourism (Vol. 23, Issue 1, pp. 19–43). https://doi.org/10.1007/s40558-020-00189-9 [4] Boomsma, C., & Steg, L. (2012). Feeling Safe in the Dark: Examining the Effect of Entrapment, Lighting Levels, and Gender on Feelings of Safety and Lighting Policy Acceptability. Environment and Behavior (Vol. 46, Issue 2, pp. 193–212). https://doi.org/10.1177/0013916512453838 [5] Blöbaum, A., & Hunecke, M. (2005). Perceived Danger in Urban Public Space. Environment and Behavior (Vol. 37, Issue 4, pp. 465–486). https://doi.org/10.1177/0013916504269643 [6] Richardson, M., Passmore, H.-A., Lumber, R., Thomas, R., & Hunt, A. (2021). Moments, not minutes: The nature-wellbeing relationship. International Journal of Wellbeing (Vol. 11, Issue 1, pp. 8–33). https://doi.org/10.5502/ijw.v11i1.1267
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Image credit: Brecht Bug (CC BY-NC-ND 2.0) 1280 words / 5-minute read Depending on where you live in the world, you may have seen them already. Some look like small computer monitors in shop windows showing opening times. Others are larger-than-life roadside billboards that seem like oversized televisions. They all use electronic displays to convey information, and at night they emit light. While these illuminated signs have different trade names, they are displacing earlier means of communicating messages at night. What does this mean for light pollution? Can these signs actually be good for the night? Digital signs: advertising of the futureThere is no doubt that illuminated signs are in demand by advertisers and other users. They allow broadcasting messages, commercial or otherwise, at all hours of the day and night. To make messages legible at night, signs use various types of illumination. "Conventional" illuminated signs often involve upward floodlighting that can spill light past the sign edges and into the night sky. While a better approach lights from the top down and uses shielded luminaires, light spill and trespass can be a problem. Even light fully captured by the sign surface ends up, in part, lost to the sky due to reflection and scattering. Digital signs make the sign surface itself luminous, usually through the controlled use of light-emitting diodes (LEDs). The light is not only bright and colorful, but also dynamic. The brightness of the message can vary to remain legible in conditions ranging from full daylight to total darkness. The displays can synthesize any color and rapidly change the assignment of light to individual pixels. The sign face can reconfigure to show a new message within a fraction of a second. Some displays can even show full-motion video. These displays are big business. Market Research Future estimates that the digital billboard market will be worth almost $42 billion worldwide by 2030. Grand View Research expects that market value to increase by about 8% a year through the 2020s. LED technology is driving this growth. As equipment prices fall, more advertisers adopt LED for its configurability and high energy efficiency. It enables them to serve more ads at a lower cost of operation. In short: the future of outdoor advertising is digital. It's a future that consists of more lighted signs at night. Your results may varyLike LED technology generally, this could be good or bad depending on the details. For this lighting application, as for others, LED has a lot of desirable characteristics. Its light is very directional, meaning that it doesn't tend to spread out much as it travels. Owners of displays can thus target the light in space to reach more of its intended audience with less waste. Further, the brightness, timing, and color are controllable, serving advertisers' needs with attention-catching visuals. This can mean using less light to convey messages compared to conventional sign lighting techniques. But, like in many area lighting applications, LED is often deployed with little concern for light waste. Digital signs often have very wide angular fields of view in the name of maximizing visibility. They're often over-bright given the strong directional nature of LED. Results of a 2010 study suggest that owners of digital signs operate them at brightnesses several times higher than those of most conventional illuminated signs. [1] Viewers can perceive them as harsh, yielding a lot of glare that makes it difficult to read the message. Digital signs broadcast their light sideways at angles that are bad for skyglow. Unlike other kinds of lighting, shielding isn't a convenient option for limiting this impact. Shielding would be so large to impose unacceptable wind loads on structures. Lack of vertical controls is the big problem. Designs direct much of the surface light upward and not toward advertisers' potential customers. We don't have much in the way of hard data on these signs' contributions to skyglow or light pollution on the ground. But we can make some educated guesses based on what we know about them. While it is arguable that they may become an important new source of light pollution, the jury remains out on their exact effect. A problem for nighttime safety?There are concerns about the impact these signs may have on public safety, given their typical brightnesses. Data suggest that digital signs are more effective than conventional ones in drawing drivers' attention away from the road. [2] When messages displayed on digital signs change very rapidly, drivers may be further distracted. [3] Yet we still do not have definitive evidence that implicates digital signs in raising the incidence of vehicle crashes. [4] It is important to distinguish the source of any presumed distraction. Is it the illumination, or is it the (changing) messages? Again, we don't know. The situation resembles that of road safety involving the use of mobile telephones. While hands-free equipment was first thought to be a safer approach, studies have not shown this to be always true. [5,6] It may be that talking on the phone while driving, rather than the manner in which one uses the phone, is most distracting. The way forwardSuccess in dealing with these concerns is a combination of technological innovation and common-sense regulation. Advertisers have an interest in ensuring that viewers see and read their messages. This can contribute in a positive way to reducing light pollution from digital signs. At the same time, viewers will not read messages on very bright signs. In fact, such signs may annoy them, causing them to form a negative opinion of advertisers. There are some signs that sign manufacturers understand this. Some companies are testing technology that limits the range of angles in which digital signs are directly viewable. This is in part due to increased municipal regulation of digital signs in the U.S. An important Supreme Court decision in City of Austin, Texas v. Reagan National Advertising of Austin, LLC (2022) affirmed the right of cities and towns to regulate these signs. Regulation ensures adequate stakeholder input and public oversight. And further design innovation will make for more efficient sign operations, lowering costs. There are emerging best practices for how to operate digital signs in ways that don't harm the night sky. In 2019, the International Dark-Sky Association released its "Guidance for Electronic Message Centers (EMCs)". This document suggests ways to operate and regulate digital signs to reduce their impacts on the nighttime environment. In the same year, the Illuminating Engineering Society introduced similar standards in its RP-39-19 document. A body of knowledge is also emerging around how to regulate digital signs in the U.S. municipal context. For example, Scenic Utah offers a "primer" for communities that seek to enact ordinances regulating these signs. The ideas are simple: Limit digital sign brightness and size; the product of these is the total light emission of the sign. Place strict constraints on allowed sign brightnesses. Impose curfews prohibiting sign illumination during overnight hours. And wherever possible, restrict digital displays to single-color messages on black backgrounds. These rules reduce light pollution from digital signs while ensuring that their messages are clearly legible. The rising market dominance of digital signs is an indicator of progress. As with previous lighting technologies, they present a challenge: to balance user needs against the equally valid need to protect the night from light pollution. Dark-skies advocates are working with municipal officials and advertising representatives. They are finding solutions that work for all involved. Many communities have no rules on the books governing the use of digital signs. It is preferable to put such rules in place before digital signs arrive in your city or town. Contact us today to find out how we can help craft durable ordinance language regulating digital signs. References[1] Luginbuhl, C., et al. (2010). Digital LED Billboard Luminance Recommendations How Bright Is Bright Enough? White paper. http://www.illinoislighting.org/resources/DigitalBillboardLuminanceRecommendation_ver7.pdf
[2] Dukic, T., Ahlstrom, C., Patten, C., Kettwich, C., & Kircher, K. (2013). Effects of Electronic Billboards on Driver Distraction. Traffic Injury Prevention, 14(5), 469-476. https://doi.org/10.1080/15389588.2012.731546 [3] Belyusar, D., Reimer, B., Mehler, B., & Coughlin, J. F. (2016). A field study on the effects of digital billboards on glance behavior during highway driving. Accident Analysis & Prevention, 88, 88-96. https://doi.org/10.1016/j.aap.2015.12.014 [4] Oviedo-Trespalacios, O., Truelove, V., Watson, B., & Hinton, J. A. (2019). The impact of road advertising signs on driver behaviour and implications for road safety: A critical systematic review. Transportation Research Part A: Policy and Practice, 122, 85-98. https://doi.org/10.1016/j.tra.2019.01.012 [5] Lipovac, K., Đerić, M., Tešić, M., Andrić, Z., & Marić, B. (2017). Mobile phone use while driving-literary review. Transportation Research Part F: Traffic Psychology and Behaviour, 47, 132-142. https://doi.org/10.1016/j.trf.2017.04.015 [6] Caird, J. K., Simmons, S. M., Wiley, K., Johnston, K. A., & Horrey, W. J. (2018). Does Talking on a Cell Phone, With a Passenger, or Dialing Affect Driving Performance? An Updated Systematic Review and Meta-Analysis of Experimental Studies. Human Factors: The Journal of the Human Factors and Ergonomics Society, 60(1), 101–133). https://doi.org/10.1177/0018720817748145 |