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dc.rights.licenseRestricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.
dc.contributorFigueiro, Mariana Gross
dc.contributorRea, Mark Stanley, 1950-
dc.contributorLeslie, Russell P.
dc.contributorKalsher, Michael J.
dc.contributor.authorSahin, Levent
dc.date.accessioned2021-11-03T08:05:59Z
dc.date.available2021-11-03T08:05:59Z
dc.date.created2014-01-17T14:43:03Z
dc.date.issued2013-08
dc.identifier.urihttps://hdl.handle.net/20.500.13015/991
dc.descriptionAugust 2013
dc.descriptionSchool of Architecture
dc.description.abstractThe findings of the laboratory studies were the first to show that long-wavelength light (630 nm) increases objective measures of alertness and performance during the afternoon and early evening hours. In addition, it was shown that white light (3000 K) is also effective in increasing alertness during the daytime and early evening hours, accompanied by better reaction time performance. Although the alerting effect of light at night has been linked to short-wavelength sensitivity of the human circadian system, present results together with previous work suggest that, the alerting effects of light are not entirely dependent on acute melatonin suppression.
dc.description.abstractFuture work should include approaches to independently modulate the activity of the photoreceptors in the eye and identify their contribution to the acute alerting response to light exposure both in laboratory and field settings. To this end, future studies should be designed to investigate the irradiance and spectral sensitivity of the light-induced alerting mechanism over the course of 24 h. Before any lighting intervention aiming at increasing alertness of the train drivers during the operation can be applicable, a number of significant hurdles would need to be overcome, the most important one is visibility. Future follow-up research should aim to conduct human factor studies to investigate the optimal solution in delivering light to the drivers' eye without compromising their visual abilities.
dc.description.abstractBy having a pioneering approach in being the first study to employ the long-wavelength light as a stimulus in studies investigating the alerting effects of light during the daytime, we believe, our findings will provide a base knowledge and excite researchers' interests in conducting future studies to better identify the mechanism behind the light-induced alertness. We also believe that showing the effectiveness of long-wavelength light on acute alertness during the day and night, could be of great interest for several layers of the general population, such as shift workers. Our results will encourage designers and decision makers to initiate more research for understanding how light affects train drivers' alertness and performance not only during the operation, but also during the breaks and rest times. Our study provides potential benefits that support accident prevention strategies that may help reduce the social and economic consequences of accidents.
dc.description.abstractBeing first to test the daytime and nighttime alerting effects of long- and short-wavelength light in an operational context in railway transportation, our results showed a promising trend, in parallel with our expectations: that red and blue light exposure increased drivers' performance in energy consumption, speed and red light violation. Although differences were not statistically significant, drivers consumed 8% and 7% less energy when they were exposed to blue and red light at night, respectively. Drivers also had less red light and speed violations under red and blue lighting conditions compared to the dim light condition at night.
dc.description.abstractAlthough, from the present results, it is not possible to identify the underlying mechanisms contributing to light-induced changes in alertness, we believe, the ipRGCs along with classical photoreceptors drive this mechanism. Our results suggest a mechanism that is more sensitive to longer-wavelengths during the daytime and to shorter-wavelengths during the nighttime indicating that the ipRGCs may either receive larger input from cone photoreceptors or weight this input more during the daytime. Another possibility is that the classical photoreceptors, such as the L-cones, mediate the alerting effects of long-wavelength light during the daytime. During the nighttime, melanopsin response seems to drive the information along with contributions of rods/and cones.
dc.description.abstractThe present thesis study investigated how various light exposures affect subjective measures of sleepiness, objective measures of alertness, and performance both during the daytime and the nighttime in the laboratory conditions and in a simulated work environment. The four laboratory studies were divided into two main groups: '1-h EEG' and '10-h EEG' studies. The 1-h EEG studies aimed at investigating how exposure to short-wavelength (470 nm, 40 lx) and long-wavelength lights (630 nm, 40 lx) during the middle of the afternoon (1430 h) and late evening (2300 h) affected objective measures of alertness (power reduction in alpha, alpha-theta, and theta ranges) on participants with regular sleep schedules. The 10-h EEG studies, on the other hand, aimed at investigating how exposures to long-wavelength (630 nm, 210 lx) and white (3000 K, 360 lx) light, at the same irradiance level (1.1 W/m2), during the daytime (0700, 1100, and 1500 hours) and nighttime (1900, 2300, and 0300 hours) affected objective measures of alertness (power reduction in alpha, alpha-theta, and theta ranges) and performance (change in visual and auditory reaction time, and tracking scores). The secondary goal of the 10-h EEG studies was to start investigating whether the alerting effect of light was dependent on the perceived color information. The objective of the field study was to investigate how exposure to short-wavelength (470 nm, 40 lx) and long-wavelength lights (630 nm, 40 lx), compared to dim light, affected driving performance of professional train drivers in a simulated work environment.
dc.description.abstractAlertness, an activation state of the brain, is influenced by the interplay between the circadian timing system (circadian process) and the duration of time awake (homeostatic process). The circadian process is regulated by the endogenous circadian pacemaker, which is synchronized daily with the environment by the 24-hour light/dark patterns incident on the retina. In diurnal species, the circadian process promotes alertness during the day and sleep at night. On the other hand, the homeostatic process accumulates sleep pressure as the number of waking hours increases. Most studies to date have associated the alerting effects of light, particularly short-wavelength light, to its ability to suppress nocturnal melatonin production, which signals nighttime to the body in diurnal species. Recent studies, however, have shown alerting effects of long-wavelength (red) light, which does not suppress melatonin. Moreover, other studies showed that white or narrowband short-wavelength lights during daytime, when melatonin levels are low, increase measures of alertness.
dc.language.isoENG
dc.publisherRensselaer Polytechnic Institute, Troy, NY
dc.relation.ispartofRensselaer Theses and Dissertations Online Collection
dc.subjectLighting
dc.titleAlerting effects of light : implications for railway transportation
dc.typeElectronic thesis
dc.typeThesis
dc.digitool.pid170172
dc.digitool.pid170173
dc.digitool.pid170174
dc.rights.holderThis electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
dc.description.degreePhD
dc.relation.departmentSchool of Architecture


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