Steep Grades Research Articles

Age-related driver injury occurrence from crashes at curve–grade combined segments

Objectives Due to their relatively complex roadway characteristics, horizontal and vertical curve segments are associated with decreased visibility and a higher risk of rollovers. Multiple studies have identified the associated risk of young and older drivers separately in such complicated driving environments. This study investigated the relationship between driver age and injury occurrence from crashes occurring along curve–grade combined segments. Methods Crash data recorded in Ohio State between 2012 and 2017 were used in this study. Driver age was categorized into 3 groups: teen (age <20 years), adult (age 20–64), and older adult (age >64). Descriptive statistics were summarized using random forest, gradient boosting, and extreme gradient boosting (XGBoost) to estimate the probability of a driver incurring an injury in case of a crash at curve–grade combined segments. The area under the receiver operating characteristics curve (AUROC) was used to select the best performing model. Partial dependence plots (PDPs) were used to interpret the model results. Results The probability of injury occurrence is different for older drivers compared to teen and adult drivers. Although teen and adult drivers showed a higher probability of sustaining injuries in crashes with an increase in the degree of curvature, older drivers were more likely to sustain injuries in roadways with higher annual average daily traffic (AADT), steeper grades, and more occupants in the vehicle. Older drivers were observed to have a higher probability of sustaining injuries during peak hours and when unrestrained compared to teen and adult drivers. Conclusions The results emphasize the significance of tailored education and outreach countermeasures, particularly for teen and older drivers, aimed at decreasing the likelihood of injuries in such driving environments. This research adds to the expanding body of knowledge concerning the age-related occurrence of driver injuries resulting from crashes at curve–grade combined segments. The study findings provide insights into the potential over- or underrepresentation of certain age groups in analyzing crash injury occurrence. The insights gained from the machine learning analysis could also assist policymakers, transportation agencies, and traffic safety experts in developing targeted strategies to enhance road safety and protect vulnerable age groups.

Impact of Band‐gap Gradient in Semi‐Transparent and Bifacial Ultra‐Thin Cu(In,Ga)Se2 Solar Cells

AbstractUltra‐thin Cu(In,Ga)Se2 (CIGSe) solar cells on transparent conductive oxide back contact reduce the material consumption of rare indium and gallium and simultaneously exhibit great potential for semi‐transparent bifacial application. For highly efficient CIGSe solar cells, a steep back Ga grading and Na treatment are expected. However, Na will promote the formation of highly resistive GaOx at the rear interface owing to Ga accumulation. In this work, the three‐stage co‐evaporation process is renewed and the effect of the deposition sequence in the first stage on the Ga distribution as well as the cross‐correlated influence of Na is explored. In particular, the standard deposition sequence of Ga+In is altered to start with In. When a thin In layer is pre‐deposited on the back contact, the fill factor and efficiency increase. The deposition of In+Ga+In in the first stage of CIGSe growth leads to efficiencies 28% (on average) higher than for the standard deposition sequence of Ga+In. Additionally, 2.74% efficiency is reached under rear and 9.32% under simultaneous front and rear illumination. Therefore, adapting the deposition sequence in the first stage of CIGSe growth is identified as a key to improving the device performance on transparent back contact.

High-concentration silver alloying and steep back-contact gallium grading enabling copper indium gallium selenide solar cell with 23.6% efficiency

Chalcopyrite-based solar cells have reached an efficiency of 23.35%, yet further improvements have been challenging. Here we present a 23.64% certified efficiency for a (Ag,Cu)(In,Ga)Se2 solar cell, achieved through the implementation of a series of strategies. We introduce a relatively high amount of silver ([Ag]/([Ag] + [Cu]) = 0.19) into the absorber and implement a ‘hockey stick’-like gallium profile with a high concentration of Ga close to the molybdenum back contact and a lower, constant concentration in the region closer to the CdS buffer layer. This kind of elemental profile minimizes lateral and in-depth bandgap fluctuations, reducing losses in open-circuit voltage. In addition, the resulting bandgap energy is close to the local optimum of 1.15 eV. We apply a RbF post-deposition treatment that leads to the formation of a Rb–In–Se phase, probably RbInSe2, passivating the absorber surface. Finally, we discuss future research directions to reach 25% efficiency.

Train Timetable Optimization for Suppressing Traction Power Fluctuations, Especially on Mountainous Railway Lines with Long, Steep Grades

Railways traversing steeply sloping plateaus in mountainous regions face severe environmental conditions. However, weak external power grids and severe fluctuations in traction power threaten the stability of the grids and pose risks to train operation. To date, little research has focused on train timetable optimization in such mountainous regions, while simultaneously considering their impact on the power grid. In the present work, we took a mountain the railway was under construction as an example to study train timetable optimization of mixed passenger and freight railways to reduce their impact on weak power grids. The 372.47-km mountain railway, on which the study was based, is an electrified railway running from Qamdo to Linzhi in western China. An optimization model of train uniformity and optimal passenger travel time was constructed, and a two-layer improved genetic algorithm proposed to obtain the optimal solution. This was shown to effectively save energy, reduce load fluctuations, and suppress voltage fluctuations to reduce railroad operational impact on the power grid.

Simulation study on the influence of longitudinal dynamic force on extreme-long heavy-haul trains

PurposeThe objective of this study is to investigate the impact of longitudinal forces on extreme-long heavy-haul trains, providing new insights and methods for their design and operation, thereby enhancing safety, operational efficiency and track system design.Design/methodology/approachA longitudinal dynamics simulation model of the super long heavy haul train was established and verified by the braking test data of 30,000 t heavy-haul combination train on the long and steep down grade of Daqing Line. The simulation model was used to analyze the influence of factors on the longitudinal force of super long heavy haul train.FindingsUnder normal conditions, the formation length of extreme-long heavy-haul combined train has a small effect on the maximum longitudinal coupler force under full service braking and emergency braking on the straight line. The slope difference of the long and steep down grade has a great impact on the maximum longitudinal coupler force of the extreme-long heavy-haul trains. Under the condition that the longitudinal force does not exceed the safety limit of 2,250 kN under full service braking at the speed of 60 km/h the maximum allowable slope difference of long and steep down grade for 40,000 t super long heavy-haul combined trains is 13‰, and that of 100,000 t is only 5‰.Originality/valueThe results will provide important theoretical basis and practical guidance for further improving the transportation efficiency and safety of extreme-long heavy-haul trains.

Vibro-acoustic performance of graded piezoelectric metamaterial plates

This work investigates the vibro-acoustic performance of graded piezoelectric metamaterial plates. A piezoelectric layer with electrodes segmented in a regular lattice is attached over a rectangular, simply-supported panel to realize the electromechanically coupled metamaterial plate, rendering a geometrically periodic structure. The grading is achieved in the electric domain, as each unit cell’s inductive shunt resonant frequency can be tuned independently. We investigate two first-order grading patterns based on linear variations along one and both dimensions of the plate and evaluate their impact on vibration attenuation, sound power, kinetic energy, and acoustic radiation efficiency. The graded metamaterial plates outperform the periodic locally resonant counterparts in vibration and radiated sound power attenuation. Moreover, sound radiation efficiency may increase within the attenuation band for steep grading patterns related to the vibration localization phenomenon. The results show that piezoelectric metamaterial plates with reconfigurable properties are an interesting alternative for enhanced vibro-acoustic performance.

Slope stress criteria as a complement to traffic stress criteria, and impact on high comfort bicycle accessibility

A high-comfort bike network that connects people's homes with their destinations is crucial to attracting more people to cycling. While avoiding high traffic stress is one critical dimension of comfort, another is avoiding steep climbs. In this study, we propose “Steepness Level” criteria that can complement Level of Traffic Stress criteria for evaluating bike networks, drawing from best-practice guidelines and behavioral studies that show tradeoffs cyclists make between steep grades and additional distance. We then apply these criteria to Montreal's bike network, along with Level of Traffic Stress criteria, to determine the impact of considering steepness limitations on bike accessibility. For some situations, adding steepness limitations has a small impact on accessibility while in others, it makes many neighborhoods inaccessible that, based on traffic stress alone, would be considered accessible. And where the topography creates a natural barrier (a ridge) with a single gently sloped corridor passing through, we demonstrate that applying low-traffic-stress treatments in this corridor would increase the fraction of central Montreal that is accessible by bike from 33% to 50%.

Design, construction and monitoring of concrete roadway pavement at extremely steep longitudinal slopes

ABSTRACT Most conventional roadway pavements are not constructed at grades greater than 15% due to construction limitations and/or motor vehicle operator safety concerns; however, there are conditions, especially in the developing world, where roadways must be built at extremely steep longitudinal slopes. Currently, there are limited published design procedures for extremely steep concrete roadways, and little guidance on either the type, shape, or spacing of sliding restraint devices for these pavements. This paper presents an original design methodology for concrete roadways at slopes of 15–60% with integral concrete lug anchors to resist sliding where the design computes a sliding factor of safety of the earth pressure resistance developed by the lug anchors as compared to the downhill forces acting on the concrete pavement from gravity, vehicle loading and vehicle braking. A case study of a concrete roadway construction project, which uses the lug anchor design methodology with slopes of 23–58% and with limited right of way, is also presented. Many valuable lessons were learned during the construction of a roadway at such steep grades, including novel ways to transport and place fresh concrete and the fabrication of specialised equipment to screed and smooth concrete on a steep slope.

Design and Implementation of an Electric Skibus Line in North Italy

To enhance the current Public Transport (PT) service in the northern Italian region of Lombardy, this work tries to plan fully a new electric Skibus line connecting the cities of Santa Caterina and Livigno. As a first try outside the city environment, the electrification study is set on a limited mountain zone hence featured by steep grades and cold temperatures. In the first part of the paper, the energy consumed by an electric bus working in such a context is assessed, and from the learned outcomes, proper charging infrastructure is proposed. From the found results, the introduction of a new electric bus line in the chosen region seems feasible. Finally, in the last part of the work the performances of an electric bus fleet are compared with that of a diesel one, in terms of fuel costs and Well-to-Wheel (WTW) emissions. The results prove that an electric fleet would be more convenient for both the economic and the environmental aspects.

Steep sulfur gradient in CZTSSe solar cells by H2S-assisted rapid surface sulfurization.

Sulfur/selenium grading is a widely used optimization strategy in kesterite thin-film solar cells to obtain a bandgap-graded absorber material and to optimize optical and electrical properties of the solar-cell device. In this work, we present a novel approach to introduce a [S]/([S] + [Se]) grading for Cu2ZnSn(S,Se)4 solar cells. In contrast to commonly used methods with slow process dynamics, the presented approach aims to create a fast sulfurization reaction on the surface of pure selenide kesterite absorbers by using highly reactive H2S gas and high sulfurization temperatures in a rapid flash-type process. With a combination of X-ray photoelectron spectroscopy, X-ray emission spectroscopy, Raman spectroscopy, and Raman-shallow angle cross sections spectroscopy, we gain depth-varied information on the [S]/([S] + [Se]) ratio and discuss the impact of different process parameter variations on the material and device properties. The results demonstrate the potential of the developed process to generate a steep gradient of sulfur that is confined mainly to the surface region of the absorber film.

Use of Field Flexural Demand Data for Reliability-Based Analysis and Design of Concrete Railroad Sleepers

Concrete is the dominant sleeper material choice for demanding locations on heavy axle load (HAL) freight railroads with steep grades, sharp curves, and high annual gross tonnage. Center flexural cracking is one of the most common factors limiting the service life of concrete sleepers in North America, and rail seat cracking has also been documented as a performance concern. As such, development and implementation of a structural design method that enables optimization of sleeper design for varied applications and loading environments will reduce initial capital cost and recurring maintenance expense. Field instrumentation has been developed to reliably capture revenue service field flexural demands, facilitating a probabilistic design method for the flexural capacity of concrete sleepers with bending data as the primary input. This paper presents a design process based on structural reliability analysis concepts whereby target values for reliability indices (β) for new designs are obtained and compared with existing designs for further design optimization. New (proposed) designs are quite different from current ones. For HAL freight, a reduction in rail seat bending capacity of approximately 40% is justified, reducing the size of the rail seat cross section by approximately the same magnitude. In most cases the proposed designs have fewer prestressing wires and a higher centroid of prestressing steel. In all cases the flexural capacities at the sleeper center and rail seat are better balanced from a structural reliability standpoint.

Geotechnical solutions for high-rise construction in the areas with significant elevation

The high attractiveness of the Black Sea coast in the Russian Federation, the ongoing work to create a world-class resort infrastructure lead to the need for the high-rise buildings’ construction and other heavy structures on steep grades that characterize most of the coastal strip. In such cases, they try to find the solutions that do not lead to a significant amount of earthwork when deepening the required number of floors under the stain of a high-rise building. However, with a large steepness of the relief, the excavation volume is always significant. Excavation during the engineering preparation of the territory and the development of deep pits leads to a loss of the slopes’ stability and, consequently, to the complex foundations’ solutions, engineering protection and overhead structures.

Peak Responses To Graded Exercise Protocols In Young Children

The Bruce protocol (Bruce) is a progressive treadmill test with an aggressive initial grade that was developed for use in adults, and is often used to assess cardiac patients. Due to the steep grade, young children may terminate the Bruce prematurely. The University of Kentucky Pediatric Exercise Physiology Lab has developed a protocol (PEP Lab) with lower grades which we hypothesized would be better tolerated and potentially elicit greater peak VO2 and cardiovascular responses. PURPOSE: To compare peak oxygen uptake (pVO2; ml·kg-1·min-1), heart rate (pHR; bpm), systolic blood pressure (pSBP; mmHg), and respiratory exchange ratio (pRER) responses to the Bruce versus the PEP Lab in 43 (22 boys) young (7-11 yr old) children of varying adiposities. We also evaluated each subject’s perception of difficulty between the two protocols. METHODS: Subjects completed the Bruce and the PEP Lab protocols in a random order 1 week apart. pVO2 and pHR were determined with an integrated metabolic system, and pSBP was determined by manual auscultation. Verbal encouragement was provided during both testing sessions and test completion based on volitional fatigue. Results are expressed as mean ± SE and significance p < 0.05. RESULTS: The Bruce versus PEP Lab pVO2 (43.6 ± 1.5 vs 43.9 ± 1.5) and pHR (186.6 ± 2.0 vs 188.2 ± 2.2) did not significantly differ. However, pSBP during the Bruce was significantly lower (136.4 ± 1.4 vs 141.3 ± 1.1) and the Bruce pRER was significantly higher (1.065 ± 0.018 vs 1.013 ± 0.014) than the PEP Lab. Bruce and PEP Lab protocol pVO2, pHR, pSBP, pRER were significantly correlated (r = 0.61, 0.47, 0.53 and 0.42, respectively). The majority (88%) of the children perceived the Bruce to be more difficult. CONCLUSIONS: : A less steep protocol can elicit similar cardiopulmonary results as the Bruce. Protocols that are perceived as less difficult may help guarantee that children do not terminate their exercise tests prematurely to reaching their true pVO2. Supported by the University of Kentucky Pediatric Exercise Physiology Lab Endowment; NIH National Center for Advancing Translational Sciences through grant number UL1TR001998. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

Operational Evaluation of Climbing Lanes on Steep Grades and Heavy Trucks

Nearly 99% of Colombian roads have two lanes. In order to improve their level of service (LOS), they have been turned into multilane roads through the doubling of existing highways without technical criteria to justify such transformation, and without considering more appropriate alternatives such as auxiliary lanes. Due to Colombia’s mountainous topography and the high weight/power ratio of the vehicles in circulation, research on auxiliary lanes has been carried out to clarify their applicability. However, operational evaluation procedures such as the Highway Capacity Manual (HCM) may not be representative for the infrastructure and vehicles in Colombia.The hypothesis is that the operational benefits of climbing lanes on two-lane roads with Colombian infrastructures and trucks are higher than the HCM estimate. The objective is to carry out an operational evaluation of the effect of auxiliary lanes on traffic in 84.000 scenarios, and to determine threshold values of operational indicators in order to provide guidance for a better design of this kind of infrastructure.The operational analysis was performed on a virtual road with an auxiliary lane with Colombian trucks and a variety of road geometry and traffic features. Traffic operations were simulated with TWOPAS, part of the Interactive Highway Safety Design Model (IHSDM), for which the computational program PEMAT was created. The results demonstrate the benefits of auxiliary lanes on the improvement of Percent Time Spent Following (PTSF) and Average Travel Speed (ATS), and define criteria for geometric design.

Formation of Ga double grading in submicron Cu(In,Ga)Se2 solar cells by pre-depositing a CuGaSe2 layer

By introducing a pre-deposited CuGaSe2 layer, a steep Ga back grading has been formed in a submicron CIGS layer with a high-temperature process for the first time.

The Heart, and: Devotional, and: Letter to My Sister, Waking in a Car in Wilmington, North Carolina

The Heart, and: Devotional, and: Letter to My Sister, Waking in a Car in Wilmington, North Carolina Colby Cotton (bio) The Heart When it stops, it stops: I'll be a washed corpseunder a field of artificial flowers, blood-drained,a wad of cotton in my septum and anus.It is what it is, my father said,when the dog had to diethe vet shaved the hind leg of our animal,and pressed a needle in him. Roses never grewas my mother hoped, despite eggshell,fertilizer, despite her walkingbelow the bedroom windows singingto the mounds of dirt, despitethe success of bougainvilleas,which were cream and flecked in pink.She watched all summer, the blue and white cupsopen on the petals of an aster, flieshover and land on the stamens. But noroses. When my sister moved out, and away,I sometimes found my father lying downin her bed, watching throughthe window, trucks shift downon the steep grade of Hinkley Hill, dustdrift from the road, and settlein the cut grass. I spent the summer swallowing gravelfrom the drive as he slept. I thought,this is what death is: the called ambulance:laying out on a bed of wheels under anesthesiaa lightness in my head and stomach—when you die, you die. I stay up nights [End Page 160] writing about the hay lofts I worked in,the radio on a power strip, strainingforgettable music through the beamsas I thumbed the incision; the smell of icein the bowls of the mortuaries tonight.A careful weighing of my brainon the scales against the heart, and liver. Devotional After Lowell I never could existin the hoot of barred owls.The writhe of rat snakesby the creeks of Jasper.You were alwayssomewhere distant:waking in a dented truckand a clean shave;or dozing under dome lightsat the wheel, breakingthe meridian toward a fieldI worked. I was alwayssomewhere waiting:pitching hay in the heatof silos and stood, steam-less,by the cattails and creek bedsas You drove the curved roadto the end of my image.I have found holinessin the cipher of rustalong wheel wells.In threshers. Have pressedmy boot into the tilled [End Page 161] ground and held inthe scent of soil. Lord,I have only listened.When I look upfrom my desk at night,there is still footfallthrough the rustof leaves. My cold toeson linoleum, tile. Once,anything could have happened:I walked through the forestwith my rifle and cockedthe hammer. I lay besidetrain tracks and bit the barrel.Lord, why did I live here.How do I die? Letter to My Sister, Waking in a Car in Wilmington, North Carolina In seven nights of silence I woke to seven drawingsof a ram, pinned along my walls. Spit six bullets in a tin cup, and trailed my handsalong the hall to the solitary screen of the porch, trying to decide what was real.How once we entered the white coops with a bucket of grain, and cut our red hair in the back lawn when it grew longas cardinal's wings. How each white feather in the grass still spins the single thread of morning.And I just sit here, and farmhands descend the riverbank. [End Page 162] Their bodies on skiffs slice the smooth, dark water.I have never wanted to live in this town, where once we walked the cold line of linento the sweet gums, and the bloodless petals of crocuses unfurled in the ditches.Before your eyes ever met coast. Before you washed sand from skin there was the aching mare,and a colt in the stall. The blue cord I plucked like guitar string. How many timesI've seen you in the cold wiring of a jay, arcing the iced lawn, I don't know.But today I felt your figure pass the rows of radishes as a light snapped on. I would walk youinto the sumac. Would breathe life into a...

Predicting injury severity and crash frequency: Insights into the impacts of geometric variables on downgrade crashes in Wyoming

Abstract Road deaths, injuries and property damage places a huge burden on the economy of most nations. Wyoming has one of the highest truck-related fatality rates among the states in the US. The high crash rates observed in the state is as a result of many factors mainly related to the challenging mountainous terrain in the state, which places extra burden on truck drivers in terms of requiring higher levels of alertness and driving skills. The difficult geometry of roads characteristic of mountainous terrain in terms of steep grade lengths adds extra risks of fatalities or injuries occurring as a result of a crash. These risks are more pronounced for truck-related crashes due to their weight and sizes. As part of the measures to reduce the incidence of truck-related crashes on mountainous areas, the Wyoming Department of Transportation (WYDOT) initiated a study to investigate causes of truck crashes on downgrade areas of Wyoming. Several studies have investigated the contributory factors to severe injury crashes but the focus has mostly been on level sections. This study analyzed the contributory geometric factors of truck crashes on downgrades by estimating three crash prediction negative binomial models. These models took into account the injury severity of the crashes. The results indicate that downgrade length, shoulder width, horizontal curve length, number of lanes, number of access points and truck traffic on the highway all impact truck-related crashes and injury frequencies on downgrades in Wyoming. The results of this study will be helpful to future downgrade road design policy aimed at reducing downgrade truck related crashes.

Impact of High-Altitude on Truck’s Climbing Speed: Case study in Qinghai-Tibet Plateau Area in China

Truck’s climbing performance is an important consideration in traffic safety, efficiency, and highway geometric design. With the infrastructure development in high-altitude area in China, more attention needs to be paid on truck’s climbing performance in such area. In this article, truck’s climbing speed in high-altitude area was examined through field tests on different grade sections at different altitudes. Truck’s speed-distance curves were built at different altitudes and the impact of altitude on truck’s climbing speed was explored based on the test results. It was shown that, within the altitude range of 3000~5000m, altitude had an obvious influence on test truck’s decelerating and accelerating performance. Truck’s speed decreased faster on steep grades and increased slower on gentle grades with the increase of the altitude. Also, the stable speed that test truck could maintain on a certain grade was lower at a higher altitude. In addition, test truck’s theoretical speed-distance curves at the sea level were estimated through truck’s dynamic model. Compared with the theoretical crawl speed, a negative effect of altitude change (from 0 to the altitude above 3000 m) was found on truck’s climbing performance.

Experimental investigation of pedestrian evacuation using an extra-long steep-slope evacuation path in a high altitude tunnel fire

This paper presents outcomes of a field experiment involving a random sample of pedestrians evacuating from a newly-constructed long tunnel at high altitude through an extra-long evacuation path with a steep grade. Adverse survival conditions include high altitude, reduced oxygen, long distance, and the steep slope of the evacuation path. Research methods include field experiments, questionnaires and interviews. Response time, route choice, movement time, speed change, and reaction to technical installations were recorded and discussed both in the tunnel and the evacuation path. The influence of adverse survival conditions was analyzed and compared with general evacuation cases. The human factors, including pedestrians’ genders, ages and emotional states were also investigated. The results of this study have resulted in guidance on evacuation planning and procedures and suggestions regarding technical installations in the tunnel, such as way-finding signs, loudspeakers, continuous lights and handrails.

Local Dynamic Stability of the Locomotion of Lower Extremity Joints and Trunk During Backward Upslope Walking

Backward slope walking was considered as a practical rehabilitation and training skill. However, its gait stability has been hardly studied, resulting in its limited application as a rehabilitation tool. In this study, the effect of walking direction and slope grade were investigated on the local dynamic stability of the motion of lower extremity joints and trunk segment during backward and forward upslope walking (BUW/FUW). The local divergence exponents (λS) of 16 adults were calculated during their BUW and FUW at grades of 0%, 5%, 10%, and 15%. Mean standard deviation over strides (MeanSD) was analyzed as their gait variability. Backward walking showed larger λS for the abduction-adduction and rotational angles of knee and ankle on inclined surface than forward walking, while λS for hip flexion-extension angle at steeper grades was opposite. No grade effect for any joint existed during BUW, while λS increased with the increasing grade during FUW. As to the trunk, walking direction did little impact on λS. Still, significant larger λS for its medial-lateral and vertical motion were found at the steeper grades during both FUW and BUW. Results indicate that during BUW, the backward direction may influence the stability of joint motions, while the trunk stability was challenged by the increasing grades. Therefore, BUW may be a training tool for the stability of both upper and lower body motion during gait.