Objective: Nighttime crashes are overrepresented on the U.S. highway system. Roadway lighting, which provides additional visibility by supplementing vehicle headlights, has been identified as an effective countermeasure to improve nighttime safety. However, the existing literature does not provide a thorough understanding of the effects of street lighting photometric characteristics on nighttime crash occurrence on roadway segments. This study aimed to investigate the relationship between lighting photometric measures and nighttime crash risk on roadway segments and develop a crash modification function/factor (CMF).
Methods: The research team collected horizontal illuminance data on 440 roadway segments between 2 successive signalized intersections in Florida for 2012–2014 and matched 4 years of nighttime and daylight crash data (2011–2014). Random parameter negative binomial models were estimated for both nighttime and daylight crash frequencies. The expected night-to-day crash odds ratio, as an equivalent of CMF, was derived from the fitted models with the correction of estimation variances. The confidence intervals (CIs) of the developed CMF were estimated using the Cox method.
Results: The coefficient of the mean of horizontal illuminance is significantly negative in the nighttime model. The coefficients of the standard deviation of horizontal illuminance are significantly positive and normally distributed in both the nighttime and daylight models. The significance of the standard deviation in the daylight model captures the confounding effects—a high standard deviation correlates with high traffic exposures, poor safety design standards, and low maintenance quality. The CMF based on the expected daylight-to-day odds ratio was developed as an exponential function of the increments and the increment squares of the mean and the standard deviation of horizontal illuminance. Its 95% CIs indicate that the CMF is almost significant over the whole range. Other significant variables contributing to nighttime crash risk include annual average daily traffic, truck percentage, segment length, access density, undivided roads, and urban/city limits.
Conclusions: Horizontal illuminance characteristics have a significant impact on nighttime crash risk on roadway segments. An increase in the mean of horizontal illuminance, indicating an improvement in average lighting level, tends to decrease nighttime crash risk; an increase in the standard deviation, representing a poor uniformity of lighting pattern on a roadway segment, is more likely to raise nighttime crash risk. Because the 2 measures are strongly correlated in a low mean range (<0.44 fc), the 2 photometric measures need to be considered together to interpret the safety effects of lighting patterns. The standard deviation shows better performance in measuring lighting uniformity on a roadway segment than the traditional ratios (max-to-min and mean-to-min). However, a new photometric measure is needed to capture the true lighting pattern influencing driver vision at night. 相似文献
This work is focused on the recovery of yttrium and zinc from fluorescent powder of cathode ray tube (CRT). Metals are extracted by sulphuric acid in the presence of hydrogen peroxide. Leaching tests are carried out according to a 22 full factorial plan and the highest extraction yields for yttrium and zinc equal to 100% are observed under the following conditions: 3 M of sulphuric acid, 10% v/v of H2O2 concentrated solution at 30% v/v, 10% w/w pulp density, 70 °C and 3 h of reaction.Two series of precipitation tests for zinc are carried out: a 22 full factorial design and a completely randomized factorial design. In these series the factors investigated are pH of solution during the precipitation and the amount of sodium sulphide added to precipitate zinc sulphide. The data of these tests are used to describe two empirical mathematical models for zinc and yttrium precipitation yields by regression analysis. The highest precipitation yields for zinc are obtained under the following conditions: pH equal to 2–2.5% and 10–12% v/v of Na2S concentrated solution at 10% w/v. In these conditions the coprecipitation of yttrium is of 15–20%.Finally further yttrium precipitation experiments by oxalic acid on the residual solutions, after removing of zinc, show that yttrium could be recovered and calcined to obtain the final product as yttrium oxide. The achieved results allow to propose a CRT recycling process based on leaching of fluorescent powder from cathode ray tube and recovery of yttrium oxide after removing of zinc by precipitation. The final recovery of yttrium is 75–80%. 相似文献
Light pollution is one of the most rapidly increasing types of environmental degradation. Its levels have been growing exponentially over the natural nocturnal lighting levels provided by starlight and moonlight. To limit this pollution several effective practices have been defined: the use of shielding on lighting fixture to prevent direct upward light, particularly at low angles above the horizon; no over lighting, i.e. avoid using higher lighting levels than strictly needed for the task, constraining illumination to the area where it is needed and the time it will be used. Nevertheless, even after the best control of the light distribution is reached and when the proper quantity of light is used, some upward light emission remains, due to reflections from the lit surfaces and atmospheric scatter. The environmental impact of this "residual light pollution", cannot be neglected and should be limited too. Here we propose a new way to limit the effects of this residual light pollution on wildlife, human health and stellar visibility. We performed analysis of the spectra of common types of lamps for external use, including the new LEDs. We evaluated their emissions relative to the spectral response functions of human eye photoreceptors, in the photopic, scotopic and the 'meltopic' melatonin suppressing bands. We found that the amount of pollution is strongly dependent on the spectral characteristics of the lamps, with the more environmentally friendly lamps being low pressure sodium, followed by high pressure sodium. Most polluting are the lamps with a strong blue emission, like Metal Halide and white LEDs. Migration from the now widely used sodium lamps to white lamps (MH and LEDs) would produce an increase of pollution in the scotopic and melatonin suppression bands of more than five times the present levels, supposing the same photopic installed flux. This increase will exacerbate known and possible unknown effects of light pollution on human health, environment and on visual perception of the Universe by humans. We present quantitative criteria to evaluate the lamps based on their spectral emissions and we suggest regulatory limits for future lighting. 相似文献
In this paper, yttrium recovery from fluorescent powder of lamps and cathode ray tubes (CRTs) is described. The process for treating these materials includes the following: (a) acid leaching, (b) purification of the leach liquors using sodium hydroxide and sodium sulfide, (c) precipitation of yttrium using oxalic acid, and (d) calcinations of oxalates for production of yttrium oxides.Experimental results have shown that process conditions necessary to purify the solutions and recover yttrium strongly depend on composition of the leach liquor, in other words, whether the powder comes from treatment of CRTs or lamp. In the optimal experimental conditions, the recoveries of yttrium oxide are about 95%, 55%, and 65% for CRT, lamps, and CRT/lamp mixture (called MIX) powders, respectively. The lower yields obtained during treatments of MIX and lamp powders are probably due to the co-precipitation of yttrium together with other metals contained in the lamps powder only. Yttrium loss can be reduced to minimum changing the experimental conditions with respect to the case of the CRT process. In any case, the purity of final products from CRT, lamps, and MIX is greater than 95%.Moreover, the possibility to treat simultaneously both CRT and lamp powders is very important and interesting from an industrial point of view since it could be possible to run a single plant treating fluorescent powder coming from two different electronic wastes. 相似文献
PROBLEM: Conventional low beams headlamps do not provide sufficient illumination for nighttime visibility on curves. METHOD: This analytical study evaluated the advantages and disadvantages of several curve-lighting strategies that involve moving one or both low beams by various amounts. Two curve radii were examined for both curve directions, using representative tungsten-halogen and high-intensity discharge low-beam patterns. The dependent variable was the maximum distance of 3-lux illumination (combined from both lamps) at a plane 0.25 m above the roadway for seven lateral positions. RESULTS: For short-radius, left and right curves, moving both lamps in parallel should substantially increase the visibility of objects in one's lane of travel, in several additional lanes of travel to the left and right, and off the road. DISCUSSION: Because of the lateral trade-offs of advantages and disadvantages for large-radius curves, additional research is needed to better understand the desirable approach for these types of curves. IMPACT ON INDUSTRY: Moving both lamps in parallel into the curve is recommended for small-radius curves. 相似文献
In view of the increasing interest in the development and dissemination of technologies for harnessing new and renewable sources
of energy in India, there have also been some efforts towards their use in the domestic lighting sector. However, the cumulative
number of Solar Photovoltaic (SPV) lighting systems such as SPV lanterns and solar home lighting systems in India is far below
their theoretical potential despite government subsidy programmes. One of the major barriers is the high capital investment
in these systems. The Clean Development Mechanism (CDM) provides industrialized countries with an incentive to invest in emission
reduction projects in developing countries to achieve a reduction in CO2 emissions at lowest cost that also promotes sustainable development in the host country. SPV lanterns and solar home lighting
systems could be of interest under the CDM because they directly displace greenhouse gas emissions while contributing to sustainable
rural development. However, only two SPV projects have been submitted under the CDM so far. This study assesses the maximum
theoretical as well as the realistically achievable CDM potential of SPV lanterns and solar home lighting systems in India.
The SPV lantern project is financially viable at a certified emissions reductions (CER) price of 34 € whereas the solar home
lighting project is financially viable at a CER price of 46 €. While the maximum mitigation volume is about 35 million tonne
CO2 on an annual basis, an estimate of achievable CER levels is done using the past diffusion trends of SPV systems. We find
that annual CER volumes could reach 0.8 to 2.4 million by 2012 and 5.6 to 13.6 million by 2020. This would require that the
government sets the subsidy level for SPV lighting systems at a level that allows them to become viable with the CER revenue.
From a macro-economic point of view this makes sense if the sustainability benefits are deemed sufficiently high to warrant
promotion of this type of project.
An analysis of the impacts on Mexican energy demand and associated carbon dioxide (CO2) emissions in the year 2005 due to efficient lighting in the commercial and residential sectors and cogeneration in the industrial
sector is presented. Estimation of CO2 abatement costs and an incremental cost curve for CO2 mitigation options are considered. These technologies are cost effective opportunities, and together are projected to reduce
CO2 emissions in 2005 by nearly 13 percent. Implementation of efficient lighting is already part of the demand side management
(DSM) programs of the Mexican state-owned utility. However, there are important barriers that may hinder the implementation
of large scale cogeneration plants. 相似文献