Risk evaluation by modeling of passing behavior on two-lane rural highways

Passing maneuver on rural two-lane highways is a complex task, which has a significant effect on capacity, level of service and safety. The maneuver is conditioned on the gap between two successive vehicles on the opposing lane. The minimum time to collision, defined as the remaining gap between the passing vehicle and the oncoming vehicle at the end of the passing process, expresses a measure of the risk involved in the passing maneuver.This paper develops a model that explains the minimum time to collision. The model formulation is based on the analysis of drivers’ passing decisions on two-lane rural highways using an interactive driving simulator. The simulator enables the collection of vehicle speeds and positions for different road and traffic scenarios. In addition to the driver simulator, participants responded to a questionnaire which collected information about their socio-demographic characteristics.The composed dataset was analyzed and processed to develop a model that predicts the risk associated with the passing behavior. Tobit regression models were found to be more suitable, in comparison to ordinary least square models and Hazard-based Duration models. The explanatory variables tested represent road geometry, traffic conditions and drivers’ characteristics. It was found that while the traffic related variables had the most important effect on the measure of risk chosen, factors related to the geometric design and the driver characteristics also had a significant contribution.     

Effects of oncoming vehicle size on overtaking judgments

During overtaking maneuvers on two-way highways drivers must temporarily cross into the opposite lane of traffic, and may face oncoming vehicles. To judge when it is safe to overtake, drivers must estimate the time-to-contact (TTC) of the oncoming vehicle. Information about an oncoming vehicle’s TTC is available in the optical expansion pattern, but it is below threshold during high-speed overtaking maneuvers, which require a large passing distance. Consequently, we hypothesized that drivers would rely on perceived distance and velocity, and that their overtaking judgments would be influenced by oncoming vehicle size. A driving simulator was used to examine whether overtaking judgments are influenced by the size of an oncoming vehicle, and by whether a driver actively conducts the overtaking maneuver or passively judges whether it is safe to overtake. Oncoming motorcycles resulted in more accepted gaps and false alarms than larger cars or trucks. Results were due to vehicle size independently of vehicle type, and reflected shifts in response bias rather than sensitivity. Drivers may misjudge the distances of motorcycles due to their relatively small sizes, contributing to accidents due to right-of-way violations. Results have implications for traffic safety and the potential role of driver-assistance technologies.     

Safety performance functions for crash severity on undivided rural roads

The objective of this paper is to explore the effect of the road features of two-lane rural road networks on crash severity. One of the main goals is to calibrate Safety Performance Functions (SPFs) that can predict the frequency per year of injuries and fatalities on homogeneous road segments. It was found that on more than 2000 km of study-road network that annual average daily traffic, lane width, curvature change rate, length, and vertical grade are important variables in explaining the severity of crashes. A crash database covering a 5-year period was examined to achieve the goals (1295 injurious crashes that included 2089 injuries and 235 fatalities). A total of 1000 km were used to calibrate SPFs and the remaining 1000 km reflecting the traffic, geometric, functional features of the preceding one were used to validate their effectiveness. A negative binomial regression model was used. Reflecting the crash configurations of the dataset and maximizing the validation outcomes, four main sets of SPFs were developed as follows: (a) one equation to predict only injury frequency per year for the subset where only non-fatal injuries occurred, (b) two different equations to predict injury frequency and fatality frequency per year per sub-set where at least one fa tality occurred together with one injury, and (c) only one equation to predict the total frequency per year of total casualties correlating accurate percentages to obtain the final expected frequency of injuries and fatalities per year on homogeneous road segments. Residual analysis confirms the effectiveness of the SPFs.     

Potential improvements of the presently applied in-service inspection of wheelset axles

Wheelset axles are safety relevant components because they are subject to high dynamic and static loads during operation. Therefore, they have to undergo periodic non-destructive examination to find potential defects before they can lead to failure. Minimizing the risk of fatigue failure for 3.5 million axles, potentially in service in Europe, was the objective of the 3.5 years R&D project EURAXLES which ended in April 2014. EURAXLES aimed to propose a global concept approach for axles design, production, and maintenance. An important objective within Work Package 5 was the analysis of the present status of in-service inspections. The strengths and weaknesses of the presently applied inspection systems and practices were evaluated with the aim to identify potential improvements provided by new technologies. That evaluation was firstly based on the results of a questionnaire which was distributed to the main European railway operators with the request to describe the testing procedures and equipment applied in their maintenance facilities. Secondly, the results of benchmark tests with presently applied ultrasonic inspection equipment were exploited for the analysis. These tests were performed at hollow axles and solid axles with implemented artificial defects.     

Crash avoidance in response to challenging driving events: The roles of age,serialization, and driving simulator platform

We examined the crash avoidance behaviors of older and middle-aged drivers in reaction to six simulated challenging road events using two different driving simulator platforms. Thirty-five healthy adults aged 21–36 years old (M = 28.9 ± 3.96) and 35 healthy adults aged 65–83 years old (M = 72.1 ± 4.34) were tested using a mid-level simulator, and 27 adults aged 21–38 years old (M = 28.6 ± 6.63) and 27 healthy adults aged 65–83 years old (M = 72.7 ± 5.39) were tested on a low-cost desktop simulator. Participants completed a set of six challenging events varying in terms of the maneuvers required, avoiding space given, directional avoidance cues, and time pressure. Results indicated that older drivers showed higher crash risk when events required multiple synchronized reactions. In situations that required simultaneous use of steering and braking, older adults tended to crash significantly more frequently. As for middle-aged drivers, their crashes were attributable to faster driving speed. The same age-related driving patterns were observed across simulator platforms. Our findings support the hypothesis that older adults tend to react serially while engaging in cognitively challenging road maneuvers.     

Synthesis and sintering of tin-doped indium oxide nanoparticles with uniform size

The urea-based hydrothermal (UBH) method can synthesize indium tin oxide (ITO) nanopowders with good monodispersity and size uniformity. However, the resulting formation of high pressure CO₂ gas by the hydrolysis of urea during the hydrothermal process is unsafe. The pressure generated by the UBH method can be lowered by connecting the hydrothermal reactor to a vessel containing sodium hydroxide solution to quickly absorb CO₂ gas. ITO nanoparticles with particle sizes of 90 ± 3 nm and 40 ± 3 nm can be produced. The size of the as-prepared nanoparticles is readily controlled by adjusting the precursor concentration. Using properly mixed nanoparticles with a volume ratio of V_40 nm:V_90 nm = 30:70 as the raw materials, ITO can be sintered to a high and consistent density of 99.3–99.5% of the theoretical density.     

Differential effects of traffic sign stimuli upon speeding in school zones following a traffic light interruption

Motorists whose journey has been interrupted by signalized traffic intersections in school zones resume their journey at a faster vehicle speed than motorists who have not been required to stop. Introducing a flashing “check speed” sign 70 m after the traffic intersections counteracts this interruptive effect. The present study examined which aspects of a reminder sign are responsible for reducing the speeding behavior of interrupted motorists. When a sign that combines both written text and flashing lights was introduced, interrupted motorists did not speed, traveling on average 0.82 km/h below the 40 km/h speed limit when measured 100 m from traffic intersections. Alternatively, when only the flashing lights were visible the interrupted motorists sped 3.36 km/h over the 40 km/h speed limit. Similar vehicular speeds were observed when only the written text was visible and when no sign was present (7.67 and 7.49 km/h over the 40 km/h speed limit, respectively). This indicates that static reminder signs add little value over the absence of a school zone reminder sign; the presence of both cues is necessary to fully offset the interruptive effect. This study also highlights the benefit of using exogenous visual cues in traffic signs to capture drivers’ attention. These findings have practical implications for the design and use of traffic signs to increase compliance with posted speed limits.     

The effects of visibility conditions,traffic density,and navigational challenge on speed compensation and driving performance in older adults

Research on how older drivers react to natural challenges in the driving environment is relevant for both the research on mental workload and that on age-related compensation. Older adults (M age = 70.8 years) were tested in a driving simulator to assess the impact of three driving challenges: a visibility challenge (clear day, fog), a traffic density challenge (low density, high density) and a navigational challenge (participants followed the road to arrive at their destination, participants had to use signs and landmarks). The three challenge manipulations induced different compensatory speed adjustments. This complicated interpretation of the other measures of driving performance. As a result, speed adjustment indices were calculated for each condition and participant and composite measures of performance were created to correct for speed compensation. (These speed adjustment indices correlated with vision test scores and subscales of the Useful Field of View^®.) When the composite measures of driving performance were analyzed, visibility × density × navigational challenge interactions emerged for hazard RT and SD of lane position. Effects were synergistic: the impact of the interaction of challenge variables was greater than the sum of independent effects. The directions of the effects varied depending on the performance measure in question though. For hazard RT, the combined effects of high-density traffic and navigational challenge were more deleterious in good visibility conditions than in fog. For or SD of lane position, the opposite pattern emerged: combined effects of high-density traffic and navigational challenge were more deleterious in fog than in clear weather. This suggests different aspects of driving performance tap different resources.     

Severity of disability related to road traffic crashes in the Spanish adult population

BackgroundThe severity of disability related to road traffic crashes has been little studied, despite the significant health and socio-economic impacts that determine victims’ quality of life.ObjectiveTo estimate the consequences of road traffic crashes on the severity of disability, in terms of individuals’ capacity to execute activities and perform tasks in their current environment, using aids.MethodsCross-sectional study conducted on community-dwelling participants in the “2008 National Survey of Disability”, with data on 91,846 households having 20,425 disabled persons, 443 of whom had disability due to road traffic crashes. We measured severity using two indicators, i.e., the Capacity (CSI) and Performance (PSI) Severity Indices.ResultsThe highest proportion of disability was mild (CSI = 70.5%; PSI = 80.8%), while 7.6% (CSI) and 4.9% (PSI) was severe/complete respectively. The moderate/severe disability rate was 0.6 per thousand on the CSI, decreasing to 0.4 per thousand on the PSI. No differences were observed by age or sex. Moderate/severely disabled persons had a fourfold higher probability of being retired or unfit for work. Mental and nervous system impairments were more closely related to moderate/severe/complete problems of capacity and performance (p < 0.001), disability for carrying out general tasks and demands, and interpersonal interactions and relationships (p < 0.001). Being permanently bedridden (p < 0.001), receiving aids (p < 0.001), family support (p < 0.05) and moving home (p < 0.05) increased with an increase in the level of severity.ConclusionRoad traffic crashes mainly cause mild disability. Moderate/severe disability is associated with lower work capacity, greater functional dependence, and increased need of aids, moving home and family support.     

Who are the traffic offenders among ethnic groups and why?

Marginalized populations, particularly ethnic minorities, are often at a higher risk of being involved in traffic crashes and committing traffic violations. Prominent explanations for this “ethnic traffic risk gap” include cultural and socioeconomic factors, usually measured at an aggregate level. In particular, it has been hypothesized that ethnic minorities commit traffic violations as a form of social resistance to what they perceive to be an oppressing regime. The current study examined the mechanisms underlying traffic violations at the individual level within a single ethnic minority, Israeli-Arabs. The study sample (n = 231) included a group of known offenders (n = 60) and non-offenders (n = 171), all of which completed the Traffic Violation Questionnaire. The results show that offenders and non-offenders tended to have different types of occupations, although these did not translate into significant differences in level of income. Offenders reported significantly lower levels of trust in some hegemonic institutions (the police, government ministries) but not others (parliament, the juridical system). However, offenders displayed remarkably different daily activity patterns, including much higher exposure to traffic (3 h/day vs. 0.75) and more complex trip patterns. Our results find little support for the social resistance hypothesis, as it fails to explain the differential treatment of hegemonic institutions. Daily activity patterns stand out as a central mechanism influencing the risk of violations. These results suggest policymakers should adopt a holistic approach for traffic safety interventions but avoid monolithic views of ethnic minorities which may lead to an inefficient use of resources.     

Prototype impact tests on ultimate impact resistance of PC rock-sheds

To confirm the ultimate impact-resistant capacity of Prestressed Concrete (PC) rock-sheds constructed over the highways in Japan, prototype impact tests are conducted by using two types of PC rock-shed frames: inverted L frame and fully rigid frame. The two types are of equal dimensions: span length=10.1 m, upper flange width=150 cm, column height=4.65 m. The impact tests are performed by iteratively and freely dropping a 3000/5000 kg steel weight onto the center of each frame covered with a 90 cm thick sand cushion. The results obtained from this study are as follows: (1) the fully rigid frame has more than 1.7 times the impact-resistant capacity of the inverted L frame with reference to input impact energy; (2) the fully rigid frame can effectively disperse the sectional forces over the whole structure; (3) the inverted L frame and fully rigid frame PC rock-sheds designed based on allowable stress design procedure have more than three and five times the margin against collapse, respectively.     

Color centers and charge state recharge in γ-irradiated Yb:YAP

Gamma-ray irradiation induced color centers and charge state recharge of impurity and doped ion in 10 at.% Yb:YAP have been studied. The change in the additional absorption (AA) spectra is mainly related to the charge exchange of the impurity Fe²⁺, Fe³⁺ and Yb³⁺ ions. Two impurity color center bands at 255 and 313 nm were attributed to Fe³⁺ and Fe²⁺ ions, respectively. The broad AA band centered at 385 nm may be associated with the cation vacancies and F-type center. The transition Yb³⁺ → Yb²⁺ takes place in the process of γ-irradiation. Oxygen annealing and γ-ray irradiation lead to an opposite effect on the absorption properties of the Yb:YAP crystal. In the air annealing process, the transition Fe²⁺ → Fe³⁺ and Yb²⁺ → Yb³⁺ take place and the color centers responsible for the 385 nm band was destroyed.     

Heating aging behavior of Al–8.35Zn–2.5Mg–2.25Cu alloy

In the present work, the influence of heating aging treatment (HAT) on the microstructure and mechanical properties of Al–Zn–Mg–Cu alloy was investigated. When the final aging temperature (FAT) was lower than 180 °C, the hardness increased with the decreasing of heating rate, however, in the case of the FAT was higher than 180 °C, the variation of hardness was opposite. The electrical conductivity of Al–Zn–Mg–Cu alloy increased with the decrease of heating rate regardless of FAT. The tensile strength, yield strength and conductivity of the Al alloy after (100–180 °C, 20 °C/h) HAT increased by 1.6%, 4.5% and 14.1% than that after T6 treatment, respectively. The precipitates sequence of HAT was coincident with that of isothermal aging, which is SSS → GP zone → η′ → η. With the increase of FAT and the decrease of heating rate, the fine precipitates became larger and the continuous η phase at grain boundary grew to be individual large precipitates. The HAT time was decreased about 80% than that for T6 treatment, indicating HAT could improve the mechanical properties, corrosion resistance and production efficiency with less energy consumption.     

Manufacturing of lightweight low-current Nb3Sn ADR magnets operating at 10 K

Adiabatic demagnetization refrigerators (ADRs) using superconducting magnets are under development for cooling many NASA instruments. Due to higher efficiency of cryocoolers at 10 K, Nb₃Sn magnets operating at 10 K are favored for space ADRs. Further, magnets need to be as light as possible and have low operating currents. This paper discusses technologies for the manufacture of lightweight, low-current Nb₃Sn magnets and reports on testing of a 35 mm bore by 60 mm long magnet. This magnet weighed less than 1 kg and successfully produced 3 T at 11.5 K with an operating current of 8 A.     

Fabrication of a PVC membrane samarium(III) sensor based on N,N′,N″-tris(4-pyridyl)trimesic amide as a selectophore

A new ion-selective electrode for Sm^3 + ion is described based on the incorporation of N,N′,N″-tris(4-pyridyl)trimesic amide (TPTA) in a poly(vinylchloride) (PVC) matrix. The membrane sensor comprises nitrobenzene (NB) as a plasticizer, and oleic acid (OA) as an anionic additive. The sensor with the optimized composition shows a Nernstian potential response of 19.8 ± 0.5 mV decade^? 1 over a wide concentration range of 1.0 × 10^? 2 and 1 × 10^? 6 mol L^? 1, with a lower detection limit of 4.7 × 10^? 7 mol L^? 1 and satisfactor applicable pH range of 3.6–9.2. Having a short response time of less than 10 s and a very good selectivity towards the Sm^3 + over a wide variety of interfering cations (e.g. alkali, alkaline earth, transition and heavy metal ions) the sensor seemed to be a promising analytical tool for determination of the Sm^3 +. Hence, it was used as an indicator electrode in the potentiometric titration of samarium ion with EDTA. It was also applied to the direct samarium recovery in binary mixtures.     

Insights into the structures,energies and electronic properties of nesquehonite surfaces by first-principles calculations

By using the first-principles calculations, the structure, energies and electronic properties of four commonly exposed surfaces for the nesquehonite crystal were investigated. The needle-like nesquehonite whisker is well developed with smooth side faces and irregular hexagonal end faces. Surface energy results indicate that the (1 0 1) surface is the most stable surface and corresponds to the side face. The density of dangling bond has a positive relationship with surface energy and the (1 0 1) surface has the least dangling bonds. In terms of relaxed surface energy, the order of relaxed surfaces is (1 0 1) < (2 0 0)-H < (3 0 1) < (2 0 0)-M < (0 0 4). During surface relaxation, the changes in the length of Mg-O bonds and hydrogen bonds contribute to generating a more stable surface with a lower surface energy. The PDOS (partial density of states) of these surfaces are mainly dominated by Mg and O atoms. A small peak value is found in the PDOS of (1 0 1) and (3 0 1) surfaces, which have less exposed Mg-O bonds. Electron transfer causes changes in the length of Mg-O bonds. A more active surface will obtain a larger value of transferred electrons during surface relaxation.     

Tribological behavior of Ni3Al matrix self-lubricating composites containing WS2, Ag and hBN tested from room temperature to 800 °C

Ni₃Al matrix self-lubricating composites (NMSC) containing varied amounts of WS₂, Ag and hBN (WAh) with weight ratio of 1:1:1 were fabricated by in situ technique using spark plasma sintering. The friction and wear properties of NMSC against the commercial Si₃N₄ ceramic ball at the load of 10 N and sliding speed of 0.234 m/s for 80 min from room temperature to 800 °C were investigated. The results showed that the tribological properties of NMSC strongly depended on the addition content of WAh. Moreover, NMSC with 15 wt.% WAh and 5 wt.% TiC exhibited the relatively lower friction coefficients and the less wear rates from RT to 800 °C. The excellent tribological behavior of NMSC with 15 wt.% WAh and 5 wt.% TiC was attributed to the synergetic action of composite lubricants of WAh and reinforced phase of TiC.     

Engineering properties of lightweight aggregate concrete made from dredged silt

Silt dredged from reservoirs can be hydrated and sintered into lightweight aggregate for producing lightweight aggregate concrete (LWAC). The densified mixture design algorithm (DMDA) was employed to manufacture LWAC using 150 kg/m³ of water at different water-to-binder ratios (w/b = 0.28, 0.32 and 0.4) using lightweight aggregates of different particle densities (800, 1100 and 1500 kg/m³). The engineering properties of the LWAC thus obtained were examined. Results show that the fresh concrete meets the design requirement of having slump of 250 ± 20 mm and slump flow of 600 ± 100 mm. With respect to hardened properties, the compressive strength, ultrasonic pulse velocity and thermal conductivity were found to decrease with increasing w/b ratio but increase with increasing aggregate density. Moreover, higher aggregate density also resulted in less shrinkage. The surface resistivity exceeding 20 kΩ-cm also matched the design objective. The experimental results prove that LWAC made from dredged silt can help enhance durability of concrete.     

Amperometric glucose sensor based on enhanced catalytic reduction of oxygen using glucose oxidase adsorbed onto core-shell Fe3O4@silica@Au magnetic nanoparticles

Monodisperse Fe₃O₄ magnetic nanoparticles (NPs) were prepared under facile solvothermal conditions and successively functionalized with silica and Au to form core/shell Fe₃O₄@silica@Au NPs. Furthermore, the samples were used as matrix to construct a glucose sensor based on glucose oxidase (GOD). The immobilized GOD retained its bioactivity with high protein load of 3.92 × 10^? 9 mol·cm^? 2, and exhibited a surface-controlled quasi-reversible redox reaction, with a fast heterogeneous electron transfer rate of 7.98 ± 0.6 s^? 1. The glucose biosensor showed a broad linear range up to 3.97 mM with high sensitivity of 62.45 μA·mM^? 1 cm^? 2 and fast response (less than 5 s).     

Preparation of SiC ceramics by aqueous gelcasting and pressureless sintering

Gelcasting is an attractive forming process to fabricate ceramic parts with complex shape. In the present work, aqueous gelcasting of SiC was studied. SiC slurry (50 vol.%) for gelcasting was prepared with sintering assistants, Al₂O₃ and Y₂O₃. The slurry was solidified in situ to green body with relative density of 55.9 ± 0.9% and flexural strength of 13.9 ± 0.7 MPa. SEM shows that ceramic powders in green body compact closely by the connection of polymer networks, and that the pores decrease greatly with the size less than 1 μm. SiC samples were also obtained by the process of gelcasting and pressureless sintering at 2000 °C for 1 h in Ar atmosphere. The relative density and flexural strength of SiC sintered body are 97.3 ± 0.4% and 637 ± 156 MPa, and the hardness and toughness are 20.68 ± 0.80 GPa and 3.85 ± 0.23 MPa m^1/2, respectively.