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This research leveraged datasets from the Strategic Highway Research Program 2 (SHRP2) Naturalistic Driving Study (NDS) to explore the potential benefits of incorporating macroscopic measures derived from NDS into traditional safety modeling. Large datasets with traversals from more than 1,700 unique drivers were used to extract driving behavior on freeway segments. New sets of time series totaling over 1,600 h of driving were developed, including vehicle dynamics exclusively during car-following, while also tracking the spacing between the instrumented vehicle and the vehicle being followed. This paper focuses on the statistical modeling of crash frequency incorporating macroscopic metrics derived from the new time-series datasets as regards the mean, median, variance, and 85th percentile of vehicle spacing, vehicle speed, and traffic density. Results of this exploration indicate that an increase in the traffic density variance, an increase in the speed variance, and a decrease in the mean vehicle spacing had significant effects associated with increases in multi-vehicle crash frequencies. These results can be used to estimate the safety effect of countermeasures that may change speed, density, and or spacing, along with changes in annual average daily traffic (AADT).

This paper describes the efforts to evaluate the safety impacts of increasing the speed limit from 55 mph to 60 mph on selected two-lane, two-way state highway road segments in Minnesota, U.S. An empirical Bayes (EB) before–after analysis was used to estimate crash modification factors (CMFs) for both segments (1,909.11 mi) and intersections (1,722 3-leg and 1,191 4-leg). Aggregate analysis conducted using all the segment and intersection data showed a 2.9% increase in total crashes, a 2.5% increase in injury (KABC) crashes, and a 0.05% reduction in the injury (KAB) crashes. These results—along with before-and-after operating speed data from another study by Minnesota Department of Transportation (MnDOT) (2019) showing that the 85th percentile operating speed remained the same and that the mean operating speeds increased by 1 mph following the speed limit increase—can lead to a conclusion that the speed limit increase from 55 mph to 60 mph had a minor effect on combined segment and intersection crashes or operating speeds. It is important to note that these results are specific to the corridors that were selected by MnDOT for the increase in speed limit; caution must be exercised when extending these to systemwide increases in speed limits in Minnesota or in other states, and when estimating long-term effects of speed limit increases as operating speeds can change over a longer period of time.

With intensified global warming, accurate quantification of hydrological processes in seasonally frozen regions, particularly with irrigated overwinter crops, is necessary to develop management strategies that promote groundwater conservation. By incorporating a physically based freeze‐thaw cycle module into the Soil and Water Assessment Tool (SWAT‐FT) model, variations of surface hydrology and groundwater dynamics were systematically assessed in North China Plain under three Shared Socioeconomic Pathways during 2041–2070 and 2071–2100 periods between the conventional and improved SWAT models. Compared to the conventional SWAT model, the SWAT‐FT model predicted an increase in soil water content, decrease in irrigation, and an increase in percolation during the growing season of winter wheat. These discrepancies resulted in a 5% higher decline rates of shallow groundwater levels simulated by the SWAT model compared to the SWAT‐FT. Additionally, the SWAT‐FT model projected that the average decline rates of shallow groundwater levels were approximately 0.90 ± 0.16 m yr−1(SSP1‐2.6), 0.60 ± 0.46 m yr−1(SSP2‐4.5), and −0.17 ± 0.53 m yr−1(SSP5‐8.5), respectively, during 2071–2100 compared to the historical period. The SWAT‐FT simulations indicated that the decline rates in shallow groundwater levels were projected to either decrease slowly or potentially increase by the end of the 21st century under the SSP5‐8.5 scenario, potentially achieving equilibrium between shallow groundwater extraction and replenishment. Our study emphasized the importance of considering the freeze‐thaw processes to evaluate groundwater variations more accurately in response to climate change effects in temperate regions with an overwinter crop. As the Earth gets warmer due to climate change, it's important to understand how water behaves in places that have cold winters. This helps us manage our water resources better. We used a computer model called SWAT to study this in North China. We added a special module to the model to simulate the freezing and thawing of water. We looked at how water on the ground's surface and underground might change in different future climate scenarios. We compared the old model to the new one. Both models said that less water would evaporate from the ground, and more would be caught by plants in all scenarios compared to the past. The models were different in how much water evaporated from the ground and moved underground. The new model showed bigger differences during the winter wheat growing season when farmers often water their fields and water goes into the ground. The new model also predicted that the level of groundwater (water underground) might change in different ways based on the climate scenario. Our study shows that understanding how freezing and thawing affect water is important for predicting how groundwater will change because of climate change in places with winter crops.

The pedestrian countdown signals (PCS) treatment involves the display of a numerical countdown that shows how many seconds are left in the flashing DON’T WALK interval. Although many studies have attempted to evaluate the safety of PCS, the results have been inconsistent for many reasons, including inadequate sample size and the inability to control for possible bias from regression to the mean and from exposure. This study performed a before-after empirical Bayes analysis using data from 115 treated intersections in Charlotte, North Carolina and 218 treated intersections in Philadelphia, Pennsylvania to evaluate the safety effects of PCS. The evaluation also included 136 reference intersections in Charlotte, and 597 reference intersections in Philadelphia. Following the implementation of PCS, total crashes decreased by approximately 8% and rear-end crashes decreased by approximately 12%, and these reductions were statistically significant at the 95% confidence level. Pedestrian crashes decreased by about 9% and this reduction was statistically significant at the 90% confidence level. Economic analysis revealed a benefit-cost ratio of 23 with a low of 13 and a high of 32.

Sandwich structures are widely used due to their light weight, high specific strength, and high specific energy absorption. Three-dimensional (3D) printing has recently been explored for creating the lattice cores of these sandwich structures. Experimental evaluation of the mechanical response of lattice cell structures (LCSs) is expensive in time and materials. As such, the finite element analysis (FEA) can be used to predict the mechanical behavior of LCSs with many different design variations more economically. Though there have been several reports on the use of FEA to develop models for predicting the post-yielding stages of 3D-printed LCSs, they are still insufficient to be a more general purpose due to the limitations associated with the lattice prediction behavior of specific features, certain geometries, and common materials along with showing sometimes poor prediction due to the computationally cheap elements out of which these models have been composed in most cases. This study focuses on the response of different LCSs at post-yielding stages based on the hexahedral elements to capture accurately the behaviors of 3D-printed polymeric lattices made of the Acrylonitrile Butadiene Styrene material. For this reason, three types of lattices such as body centered cubic, tetrahedron with horizontal struts, and pyramidal are considered. The FEA models are developed to capture the post-yielding compressive behavior of these different LCSs. These models are used to understand and provide detailed information of the failure mechanisms and relation between post-yielding deformations and the topologies of the lattice. All of these configurations were tested before experimentally during compression in the z-direction under quasi-static conditions and are compared here with the FEA results. The post-yielding behavior obtained from FEA matches reasonably well with the experimental observations, providing the validity of the FEA models.Graphical Abstract

Nitrogen (N) loss is a significant source of water quality pollution in alluvial watersheds. However, the mechanisms linking N loss and elevated CO2concentration (eCO2) are not well recognized. In this study, we comprehensively calibrated the SWAT model equipped with a dynamic CO2input and response module to investigate the response mechanisms between multiform N losses and eCO2in a representative large‐scale watershed. Results revealed nitrate loss under eCO2exceeding 100% in some upstream zones under the SSP5‐8.5 scenario (P< 0.05) compared to the constant CO2concentration. This was directly related to the great increase in hydrological variables, which were the carriers of N losses, and the intensive inputs of N fertilizer. Results also found that nitrate leaching was greater than the other two processes for future periods, peaking at 309.3%, as compared to the baseline period. The findings suggested reducing fertilizer inputs by 10%–20% was promising, especially for reducing nitrate loss through runoff and leaching by up to 17.7% and 12.2%. This study explored the mechanisms of increased N loss in response to eCO2and provided scientific evidence for early warning and making decisions to improve water quality at a large watershed scale.

Cross-sectional and the empirical Bayes (EB) before–after are two of the most common methods for estimating crash modification factors (CMFs). The EB before–after method has now been accepted as one way of addressing the potential bias caused by the regression to the mean problem. However, sometimes before–after methods may not feasible because of the lack of data from before and after periods. In those cases, researchers rely on cross-sectional studies to develop CMFs. However, cross-sectional studies may provide biased CMFs through confounding. The propensity score (PS) matching method, along with cross-sectional regression models, is one of the methods that can be used to address confounding. Though PS methods are widely used in epidemiology and other studies, there are only a few studies that have used PS matching methods to estimate CMFs. The intent of this study is to evaluate and compare the performance of cross-sectional regression models using PS matching methods with the results from the EB and traditional cross-sectional methods. The comparisons were conducted using two carefully selected simulated datasets. The results indicate that optimal propensity score distance (PSD) matching with maximum variable ratio of 5 performed quite well compared with the EB before–after and the traditional cross-sectional methods.

This paper focuses on the compression behavior of additively manufactured or three-dimensional printed polymer lattice structures of different configurations. The body-centered cubic lattice unit cell, which has been extensively investigated for energy absorption applications, is the starting point for this research. In this study, the lattice structure based on the body-centered cubic unit cell was modified by adding vertical struts in different arrangements to create three additional configurations. Four lattice structure designs were selected for comparison: the basic unit cell (body centered cubic), body centered cubic with vertical struts added to all nodes in the lattice, body centered cubic with vertical struts added to alternate nodes in the lattice, and body centered cubic with gradient in the number of vertical bars in the lattice. Samples of all four designs were prepared using acrylonitrile–butadiene–styrene polymer by three-dimensional printing. The stiffness, failure loads, and energy absorption behaviors of all four configurations were determined under quasi-static compression loading. Specific properties were calculated by normalizing the test properties by the sample mass. It is observed from experimental data that selective placement of vertical support struts in the unit cell influences both the absolute and specific mechanical properties of lattice structures.

SWAT simulated corn LAI and yield of full irrigation matched measured data well.Stress algorithms adjusted corn LAI and yield unsatisfactory for limited irrigation.Stress algorithms only consider dominant stress factors such as water and temperature.Stress algorithms only adjust LAI and biomass rather than crop growth parameters.Long‐term measured field data are needed to develop new stress algorithms. Decreased groundwater levels of the Ogallala Aquifer have increased interest in simulating crop responses to deficit irrigation strategies to evaluate the sustainable irrigation management for profitable crop production. However, the ability of widely used simulation models to accurately represent crop responses to deficit irrigation is not thoroughly evaluated. Therefore, the objective of this research was to evaluate the efficacy of the plant stress algorithms in Soil and Water Assessment Tool (SWAT) to simulate corn (Zea maysL.) responses to deficit irrigation treatments. Results showed simulated corn leaf area index (LAI), biomass, and yield under full irrigation scenarios matched measured data reasonably well at two study sites. However, clear reductions in model performance statistics for corn LAI simulations were found under the deficit irrigation scenarios for both sites (Nash‐Sutcliffe efficiency [NSE] <0.49; percent bias [PBIAS] >14%). Additionally, considerable overestimation of yield occurred in the deficit irrigation scenarios for both sites (PBIAS >30% in most years). The unsatisfactory results from simulations of both LAI and yield under the deficit irrigation scenarios suggested potential deficiencies of the plant stress algorithms in SWAT. Two apparent limitations of the plant stress algorithms were (i) the equation for computing actual plant growth factor using a singular stress factor, determined by the maximum value of four plant stress factors of water, temperature, nitrogen, and phosphorus, and (ii) the computed actual plant growth factor only adjusting potential daily accumulations of LAI rather than modifying the shape of the LAI development by adjusting related parameters.

A significant portion of both fatal and total crashes occurs at intersections in the United States. Skew angle may be a significant contributor to these crashes. This paper examines the effects of intersection angle on intersection safety performance. With seven years of crash data from Minnesota and five years of crash data from Ohio, random forest regression data mining and negative binomial regression models were developed to estimate crash modification functions at three-leg and four-leg stop-controlled intersections with two-lane and multilane major legs. Where possible, the results were compared between the two states and used to develop average crash modification function curves. This study shows that over half of the intersection types experience the highest number of predicted crashes when the intersection angle between roadway legs is between 50 degrees and 65 degrees. These results have practical implications for engineers and safety professionals. First, the crash modification function curves supplement and revise the guidance for intersection angle in the Highway Safety Manualand Policy on Geometric Design of Highways and Streets. Second, the functions offer new guidance to agencies planning intersection improvements. Third, the crash modification functions can be used to determine the safety effect of changes in intersection angle.

This paper documents and illustrates a practice-ready procedure for estimating changes in crash frequency for specific application circumstances for three intelligent transportation system treatments—Closed Circuit Television Cameras (CCTV), Dynamic Message Signs (DMS), and Road Weather Information Systems (RWIS). The procedure will allow an agency to directly evaluate the change in safety that may be associated with a contemplated treatment. In effect, the approach mimics the application of a Crash Modification Function (CMFunction) in that each potential application will, in principle, have its own Crash Modification Factor (CMF). The procedure uses an empirical Bayes framework with safety performance functions (SPFs) for treatment and non-treatment reference sites. The paper also presents those SPFs, which were developed from Pennsylvania freeway data. In principle, this cross-sectional approach can be applied, as it has been, for other safety treatments where safety effects vary with application circumstance and where that variability cannot be captured with conventional before–after studies.

This study determined the crash modification factors (CMFs) associated with horizontal curve realignment using the before–after empirical Bayes method and compared the results from published CMFs from cross-sectional studies. This evaluation used data from rural, two-lane roads in California, North Carolina, and Ohio. The evaluation revealed a 68% reduction in total crashes, a 74% reduction in injury and fatal crashes, a 78% reduction in run-off-road and fixed object crashes, a 42% reduction in crashes during dark conditions, and an 80% reduction in wet-road crashes, all of which were statistically significant at the 95% confidence level. The results pertain to a range of site characteristics, the most important of which is the range of before and after degree of curve. The average degrees of curve in the before and after periods were 18.1 (with a minimum of 3.2 and a maximum of 52.1) and 6.9 (with a minimum of 0.0 and a maximum of 16.3), respectively. The average central angle of the curves was approximately 42° (with a minimum of 1 and a maximum of 117). The CMFs from this before–after evaluation are lower compared to CMFs estimated from two previous cross-sectional studies. There is a need for further research with a larger sample of sites to assess the reliability of the CMFs obtained from this before–after evaluation.

This paper presents the results of an evaluation of the flashing yellow arrow (FYA) treatment using data from signalized intersections in Nevada, North Carolina, Oklahoma, and Oregon. The evaluation method was an empirical Bayes before–after analysis. The treatments were divided into seven categories depending on the phasing system in the before period (permissive, protected–permissive, or protected), phasing system in the after period (FYA permissive or FYA protected–permissive), the number of roads where the FYA was implemented (one road or both roads), and the number of legs at the intersections (three or four). The first five treatment categories involved permissive or protected–permissive phasing in the before period. Intersections in these five treatment categories experienced a reduction in the primary target crashes under consideration: left turn crashes and left turn with opposing through crashes. The reduction ranged from 15% to 50%, depending on the treatment category. Intersections that had at least one protected left turn phase in the before period and had FYA protected–permissive left turn phase in the after period experienced an increase in left turn crashes and left turn with opposing through crashes, indicating that replacing a fully protected left turn with FYA will likely cause an increase in left turn crashes.

This study focuses on analysis of future climate change impacts on West Nishnabotna Watershed, using climate model data and an open source hydrological model—Soil and Water Assessment Tool (SWAT), which is run in Quantum Geographical Information System(QGIS) environment. The data required to simulate hydrological processes using SWAT plugin in QGIS (QSWAT) are Digital Elevation Model, land use/landcover map, soil map, slope map and climate data of the study area. The required climate parameters like maximum temperature, minimum temperature and precipitation are obtained from North American Regional Climate Change Assessment Program climate model database which are bias corrected for the study area using linear scaling method. SWAT model is setup using observed climate and the model calibration and validation is performed using SWAT Calibration and Uncertainty Program (SWAT-CUP). Simulations are run for historic (1971–1999) and future (2041–2069) climate conditions for the stream flow prediction. The climate change impact analysis like anomalies and trends in the hydrological regime of the watershed are carried out based on QSWAT simulation results.

The objective of this study was to develop crash modification factors for four treatment types: rectangular rapid-flashing beacon (RRFB), pedestrian hybrid beacon (PHB), pedestrian refuge island (RI), and advance yield or stop markings and signs (AS). From 14 cities throughout the United States, 975 treatment and comparison sites were selected. Most of the treatment sites were selected at intersections on urban, multilane streets, because these locations present a high risk for pedestrian crashes and are where countermeasures typically are needed most. For each treatment site, relevant data were collected on the treatment characteristics, traffic, geometric, and roadway variables, and the pedestrian crashes and other crash types that occurred at each site. Cross-sectional regression models and before–after empirical Bayesian analysis techniques were used to determine the crash effects of each treatment type. All four of the treatment types were found to be associated with reductions in pedestrian crash risk, compared with the reductions at untreated sites. PHBs were associated with the greatest reduction of pedestrian crash risk (55% reduction), followed by RRFBs (47% reduction), RIs (32% reduction), and AS (25% reduction). The results for RRFBs had their basis in a limited sample and must be used with caution.

This study presents an application of the SWAT model (Soil and Water Assessment Tool) in two meso-scale catchments in Poland (Upper Narew and Barycz), contrasting in terms of human pressures on water quantity and quality. The main objective was multi-variable and multi-site calibration and validation of the model against daily discharge, sediment and nutrient loads as well as discussion of challenges encountered in calibration phase. Multi-site calibration and validation gave varied results ranging from very good (daily discharge) to acceptable (sediment, nitrogen and phosphorus loads in most of gauges) and rather poor (individual gauges for all variables) in both catchments. The calibrated models enabled spatial quantification of water yield, sediment and nutrient loads, indicating areas of special concern in terms of pollution, as well as estimation of contribution of pollution from different sources, indicating agriculture as the most important source in both catchments. During the calibration process a number of significant issues were encountered: (i) global vs. local parametrization, (ii) simulation of different pools of water quality parameters in reservoirs and streams and (iii) underestimation of NO3-N loads in winter due to farmers practices. Discussion of these issues is hoped to aid SWAT model users in Poland in a deeper understanding of mechanisms of multi-variable and multi-site calibration.

This paper describes a study that used data from rural two-lane roads in Arizona to illustrate two issues. One issue is the importance of selecting an appropriate sample size for calibrating the Highway Safety Manual(HSM) predictive models based on the desired accuracy of the calibration factor, instead of relying on the guidance from the HSM (the HSM recommends 30 to 50 sites with at least 100 crashes per year but provides no statistical basis for this guidance). The second issue is the usefulness of estimating calibration functions when individual calibration factors do not provide a proper fit of the local data. On the basis of the outcome of the exploration of these two issues, this study recommends a simple calibration function for predicting total crashes on rural two-lane roads in Arizona. This paper also provides a brief overview of a procedure in Microsoft Excel that can be used by practitioners (after appropriate training) to estimate simple calibration functions.

Diverging diamond interchanges (DDIs) are increasingly popular because they provide improved traffic operations and cost savings. On the basis of theory, DDIs should be safer than conventional diamonds, but previous empirical safety studies have been limited. The objectives of this work were, therefore, to conduct a broader safety evaluation of DDIs and to recommend a crash modification factor (CMF) for the conversion of a conventional diamond to a DDI. The team analyzed seven of the earliest DDIs in the United States. Four were in Missouri and other sites were in Kentucky, New York, and Tennessee. The team collected more than 28 site years of crash and other data before intersection conversion and more than 19 site years of data after their conversion. The primary analysis was before and after with comparison sites to account for trends and potential simultaneous event biases. The results showed that crashes were reduced at most of the sites, and the team recommended a CMF of 0.67, meaning that installation of a DDI to replace a diamond should reduce all crashes by 33%. The reduction in injury crashes was even larger, with the team recommending a CMF of 0.59. Other analyses indicated that DDI installation should mean a substantial reduction of angle and turning crashes, with some reduction in rear-end crashes as well, although rear-end crashes will still be the dominant crash types after DDI installation. Clearly, DDIs offer potential safety benefits, and agencies should consider them strongly as replacements for conventional diamonds.

High nitrate concentrations in streams have become a widespread problem throughout Europe in recent decades, damaging surface water and groundwater quality. The European Nitrate Directive fixed a potability threshold of 50 mg L−1for European rivers. The performance of the Soil and Water Assessment Tool model was assessed in the 1110‐km2Save catchment in southwestern France for predicting water discharge and nitrate loads and concentrations at the catchment outlet, considering observed data set uncertainty. Simulated values were compared with intensive and extensive measurement data sets. Daily discharge fitted observations (Nash‐Sutcliffe efficiency coefficient = 0.61, R2= 0.7, and PBIAS = −22%). Nitrate simulation (1998–2010) was within the observed range (PBIAS = 10–21%, considering observed data set uncertainty). Annual nitrate load at the catchment outlet was correlated to the annual water yield at the outlet (R2= 0.63). Simulated annual catchment nitrate exportation ranged from 21 to 49 kg ha−1depending on annual hydrological conditions (average, 36 kg ha−1). Exportation rates ranged from 3 to 8% of nitrogen inputs. During floods, 34% of the nitrate load was exported, which represented 18% of the 1998–2010 period. Average daily nitrate concentration at the outlet was 29 mg L−1(1998–2010), ranging from 0 to 270 mg L−1. Nitrate concentration exceeded the European 50 mg L−1potability threshold during 244 d between 1998 and 2010. A 20% reduction of nitrogen input reduced crop yield by between 5 and 9% and reduced by 62% the days when the 50 mg L−1threshold was exceeded.

The Soil and Water Assessment Tool (SWAT) model has emerged as one of the most widely used water quality watershed‐ and river basin–scale models worldwide, applied extensively for a broad range of hydrologic and/or environmental problems. The international use of SWAT can be attributed to its flexibility in addressing water resource problems, extensive networking via dozens of training workshops and the several international conferences that have been held during the past decade, comprehensive online documentation and supporting software, and an open source code that can be adapted by model users for specific application needs. The catalyst for this special collection of papers was the 2011 International SWAT Conference & Workshops held in Toledo, Spain, which featured over 160 scientific presentations representing SWAT applications in 37 countries. This special collection presents 22 specific SWAT‐related studies, most of which were presented at the 2011 SWAT Conference; it represents SWAT applications on five different continents, with the majority of studies being conducted in Europe and North America. The papers cover a variety of topics, including hydrologic testing at a wide range of watershed scales, transport of pollutants in northern European lowland watersheds, data input and routing method effects on sediment transport, development and testing of potential new model algorithms, and description and testing of supporting software. In this introduction to the special section, we provide a synthesis of these studies within four main categories: (i) hydrologic foundations, (ii) sediment transport and routing analyses, (iii) nutrient and pesticide transport, and (iv) scenario analyses. We conclude with a brief summary of key SWAT research and development needs.

Data from 282 signalized intersections in Charlotte, North Carolina, were used to examine the safety effect of converting the signals to composite LED bulbs. An empirical Bayes before-and-after method was used for the evaluation. Since this was a blanket installation by the city of Charlotte, a comparison group of stop-controlled intersections was used to account for possible trends during the study period. Crash modification factors (CMFs) were estimated for three- and four-leg intersections for eight different crash types including crashes at dawn and dusk and in dark conditions. For three-leg intersections, all CMFs were higher than 1.0; this factor indicates a possible increase in crashes due to the LEDs. However, none of these CMFs were statistically different from 1.0 at the .05 significance level. For four-leg intersections, the CMFs associated with rear-end crashes were lower than 1.0 and statistically significant at the .05 level; this finding indicates a reduction in these crash types following the changeover to the LEDs. There was substantial difference between the sites in terms of the effect of the LEDs. The reasons for these differences are not known at this time. Future research should investigate whether LEDs are more or less beneficial depending on the characteristics of the intersection including type of area, sight distance, traffic volume, and phasing scheme.

This study examined the safety impacts of converting late nighttime flash operation to normal phasing operation at signalized intersections by using the empirical Bayes, the univariate full Bayes, and multivariate full Bayes before-and-after methods. Data were obtained from the North Carolina Department of Transportation for 61 treatment sites and 395 reference intersections that remained on late nighttime flash operation from 2000 to 2007. The results from the empirical Bayes method are almost identical to those of the univariate full Bayes. The full Bayes method offered more flexibility in selecting the functional form of expected crashes at similar sites (similar to the safety performance function in the empirical Bayes) and in addressing uncertainty in the data. Compared with the univariate full Bayes, the multivariate full Bayes with the multivariate Poisson lognormal (MVPLN) model provided better results based on much lower deviance information criterion values. The MVPLN model was favored and the recommended crash reduction factors are 48% (±66%), 53% (±8%), and 57% (±7%) for nighttime total, injury and fatal, and frontal impact crashes, respectively.

Two related evaluation studies that were conducted under NCHRP Project 17-35 are presented. The research objective was to use the most appropriate analytical methods and the best available data to build on previous research in developing crash modification factors (CMFs) for two treatments for reducing crashes related to traffic signal change intervals: modifying the change interval and installing dynamic signal warning flashers. Three evaluation methods were used as appropriate—the empirical Bayes before-after method, the comparison group before-after method, and cross-sectional multiple regression models. A secondary objective of using cross-sectional models for some evaluations was to examine the comparability of before-after and cross-sectional studies, a subject of topical interest in CMF development. There was a general safety benefit to installing dynamic signal warning flashers, with indications that crash reductions could be obtained overall and for several crash types, including injury, angle, and heavy-vehicle crashes. For the change-interval modification, the before-after study results showed significant reductions (at the 5% level) in total, injury, and rear-end crashes under various scenarios. For both treatments, the results from the cross-sectional analysis were relatively consistent with those from the before-after analysis.

Money should be spent on research that promises the most value for the dollar, but how does one estimate the value of research? This paper suggests a logical and quantitative approach for estimating the dollar value of a class of proposed road safety research projects that aim to estimate the safety effects of various actions. The purpose of such research is to improve the ability to predict the safety effects of future actions because more accurate predictions would result in fewer incorrect decisions. With more correct decisions, investment is more cost-effective. This final outcome is what gives such research its value. The task of assigning a dollar value to proposed research is doable. The logic and the computations are described. The estimated dollar value, when coupled with the cost of research, can be used to prioritize proposed research projects.

The performance of a pedestrian safety device, the rectangular rapid flash beacon (RRFB), was evaluated at a street crossing of Florida's Pinellas Trail, a shared-use path where the majority of trail users were bicyclists. An elevated video camera beside the trail and several hundred feet from the crossing was used to collect before-and-after data for more than 1,000 bicyclists and pedestrians. The delay before trail users began to cross was reduced after the RRFB was installed. Bicyclists and pedestrians yielded considerably less, and motorists considerably more, after the installation. Yielding by motorists increased from 2% before to 35% after installation of the RRFB. When the flasher was activated, motorist yielding was 54%. In the before period, 82% of trail users were able to cross the intersection, whereas 18% were trapped in the middle. In the after period, these values were 94% and 6%, respectively. Installation of the RRFB increased the safety of trail users at the crossing. However, the device is not fail-safe, and communities that use it at trail crossings should be aware of this limitation. Education could help increase the percentage of trail users who push the button to activate the RRFB and increase motorist knowledge about the requirement to yield to pedestrians at crossings. Periodic police enforcement or the development of a passive detection system could also be helpful.

Crash modification factors (CMFs) are listed in the Highway Safety Manual and other authoritative publications. This information does not allow the reader to distinguish between the predictions of safety effect that can be made confidently and are likely to lead to correct decisions and those that can easily be wrong. Nor can it be known how transferable past research results are to decisions about future actions to be implemented under different circumstances. The conceptual framework described in this paper aims to provide guidance for research about CMFs and for meta-analyses. The central claim is that CMFs are random variables and are not universal constants that apply everywhere at all times. The smaller the standard deviation of a CMF, the more confident the related decision making can be. Therefore, the aim of research into CMFs is to reduce their standard deviations. Ways to do so efficiently are indicated. The requisite theory and equations are provided.

This study estimated crash modification factors (CMFs) from before-after evaluations of two treatments targeted at reducing left-turn crashes at signalized intersections: (a) changes from permissive to protected-permissive phasing and (b) the implementation of a flashing yellow arrow for permissive left turns. Results of the first evaluation—based on 59 intersections in Toronto, Ontario, Canada, and 12 in North Carolina—indicated a substantial reduction in left-turn opposing through crashes, especially at intersections at which more than one leg was treated, and a small percentage increase in rear-end crashes. For the second evaluation (the implementation of the flashing yellow arrow)—based on data from 51 signalized intersections in Oregon, Washington State, and North Carolina—the results indicated a safety benefit at locations with some kind of permissive left-turn operation before and a disbenefit at locations that had a protected-only operation before. The study estimated the standard deviation of the distribution of the CMF in addition to the conventionally estimated standard error of the mean CMF value. For several CMFs, the standard deviation of the distribution was larger than the standard error of the mean value of the CMF and indicated a substantial variation in the effect of the treatment across different sites. This finding indicates the need for further research into the development of crash modification functions instead of CMFs and for the use of large treatment databases to undertake a more extensive disaggregate analysis of the safety effects. The finding also emphasizes the importance of providing a more explicit consideration of CMF variability in future editions of the Highway Safety Manual.

Crash modification factors (CMFs) are listed in the Highway Safety Manual and other authoritative publications. This information does not allow the reader to distinguish between the predictions of safety effect that can be made confidently and are likely to lead to correct decisions and those that can easily be wrong. Nor can it be known how transferable past research results are to decisions about future actions to be implemented under different circumstances. The conceptual framework described in this paper aims to provide guidance for research about CMFs and for meta-analyses. The central claim is that CMFs are random variables and are not universal constants that apply everywhere at all times. The smaller the standard deviation of a CMF, the more confident the related decision making can be. Therefore, the aim of research into CMFs is to reduce their standard deviations. Ways to do so efficiently are indicated. The requisite theory and equations are provided.

Shared lane markings (sharrows) convey the message that motorists and cyclists must share the travel way on which they are operating. The purpose of the markings is to create improved conditions for bicycling by clarifying where cyclists are expected to ride and reminding motorists to expect cyclists on the road. A before-after evaluation was conducted to compare how cyclists and motorists operated on a street with parallel parking in Cambridge, Massachusetts, with no markings versus with sharrows placed 10 ft (3.05 m) from the curb. This evaluation, which was part of a broader FHWA study on sharrows, was intended to help determine whether an alternative to the 11-ft (3.4-m) spacing recommended in the 2009 version of the Manual on Uniform Traffic Control Devices would be effective. Operational and safety measures for bicyclists and motorists were examined. Overall, safety effects appeared to be associated with the installation of the sharrows placed 10 ft (3.05 m) from the curb. Perhaps the most important effect was the 14-in. (36-cm) increase in spacing between motor vehicles in the travel lane and parked motor vehicles when no bicycles were present. This effect increased the operating space for bicyclists. Many variables related to the interaction of bicycles and motor vehicles also showed positive operational and safety effects.

Empirical Bayes (EB) before-after evaluations provide the average safety effectiveness estimate for safety improvement treatments that have been implemented on a group of sites. When multiple improvements have been installed at each site, a single effectiveness estimate is provided for the combination of improvements. To obtain individual safety effectiveness estimates for the improvements by the current EB method, separate studies of each improvement must be conducted. Alternative EB methods may be applied, however, when sites that have the combined improvements installed and sites that have all but the desired improvement to be estimated are both available. This paper examines the safety evaluation methodology, safety effect estimators, and statistical test of significance for these alternative EB methods. The recent study of the safety edge treatment is used to illustrate these methods. Recommendations include the conduct of individual EB analyses for study sites with and without the desired treatment and the estimation of the effect directly from the results. It was found that a statistical test of significance could be conducted by generating a confidence interval from the estimated variance of the estimates. Areas for further research were also identified.

Many studies have been conducted to estimate the traffic safety impacts of roadway construction. Overall, the results of the analyses have varied widely, a variance traditionally attributed to site-to-site and project-to-project differences. In this paper, researchers describe an effort to use empirical Bayesian (EB) techniques to develop crash modification factors (CMFs for construction zones on the basis of temporal factors). Specifically, separate CMFs were estimated for various conditions, including time-of-day (e.g., daytime, nighttime), work status (e.g., activity, inactivity), and temporary traffic control (e.g., lane closure, no lane closure). Daily project inspector diaries from 64 freeway construction projects in four states were analyzed to determine hours of work, hours and locations of temporary lane closures, and the number of travel lanes closed during each work period. Researchers used EB methods in a before-during study design to investigate the safety impacts of the work zone conditions. Work activities that required the temporary closure of one or more travel lanes resulted in the largest CMFs (i.e., the largest increases in crashes), followed by periods of work activity that did not require a lane closure (i.e., work was occurring in the median or beyond the edge of the travel lanes). The lowest increase in crashes occurred during periods when work was not occurring at a project. The CMFs during work activity did not vary significantly between daytime and nighttime conditions when there was a lane closure. The results suggest that EB methods can be useful in assessing temporal factors that influence road safety.

A coordinated effort is under way to develop a Highway Safety Manual (HSM) for use in making quantitative estimates of the safety performance of specific highway types and quantitative estimates of proposed improvements to specific highway types. The highway types being addressed in the first edition of HSM are rural two-lane highways, rural multilane highways, and urban and suburban arterials. Explicit consideration of pedestrian safety on urban and suburban arterials is considered critical to implementation of the first edition of HSM. The objective of the present research was to develop a methodology for quantifying the effects of existing site characteristics and proposed improvements on urban and suburban arterials on pedestrian safety. The pedestrian safety prediction methodology has been developed to function as a component of the overall safety prediction methodology for urban and suburban arterials proposed for the first edition of HSM. In the present research, a methodology for prediction of vehicle-pedestrian collisions at signalized intersections was developed. This methodology includes base models for three- and four-leg signalized intersections and several accident modification factors.

Automated speed enforcement programs were evaluated worldwide to ascertain the effectiveness of such programs at achieving safety benefits. Unlike previous reviews on this topic, a critical review process was used to determine the most likely range of probable safety effects of fixed and mobile automated speed enforcement programs. Among the 90 studies from 16 countries that were initially identified as potential safety evaluation studies, 13 met the criteria for detailed methodological review. On the basis of evidence from the best-controlled evaluation studies, injury crash reductions in the range of 20% to 25% appear to be a reasonable estimate of site-specific safety benefit from conspicuous, fixed-camera, automated speed enforcement programs. No conclusions were reached regarding site-specific effects of mobile enforcement programs. Estimates of systemwide crash reductions likely attributable to covert, mobile speed enforcement programs were based on different subsets of crashes (daytime casualty crashes and daytime speed-related crashes) and were limited to two studies, but also were in the range of 20% to 25%.

This study conducted a before-after evaluation by means of the empirical Bayes methodology for four types of treatments at signalized intersections with data from Winston-Salem, North Carolina. The results indicated that changing to protected left-turn phasing from permissive or permissive-protected phasing could lead to a virtual elimination of left-turn crashes but other crashes, which were likely to be less severe, could increase. Conversion from nighttime flashback to regular phasing seemed effective in reducing nighttime crashes. Replacing 8-in. signal heads with 12-in. heads seemed effective in reducing right-angle crashes, but this measure could increase other, less-severe crashes. Adding another red-signal lens to an existing one or changing from permissive to permissive-protected left-turn phasing did not seem particularly effective in reducing crashes, but these results were not definitive because they were based on a limited number of sites. Further research using data from other jurisdictions is needed, so that more definitive conclusions can be made about the safety effectiveness of these treatments.

FHWA organized a pooled fund study of 26 states to evaluate low-cost safety strategies as part of its strategic highway safety effort. One of the strategies chosen to be evaluated was the installation of flashing beacons at stop-controlled intersections. The intent of flashing beacons is to reduce the frequency of crashes related to driver unawareness of stop control. Geometric, traffic, and crash data were obtained at stop-controlled intersections for 64 sites in North Carolina and 42 sites in South Carolina. Empirical Bayes methods were incorporated in a before-after analysis to determine the safety effectiveness of installing flashing beacons while accounting for potential selection bias and regression-to-the-mean effects. Overall, installation of flashing beacons in North Carolina resulted in statistically significant reductions in total, angle, and injury-plus-fatal crashes. The intersections in South Carolina experienced little change following the introduction of flashing beacons, but the combined results from both states still indicated a statistically significant reduction in angle and injury-plus-fatal crashes. An economic analysis indicated that standard flashing beacons can achieve a 2:1 benefit-cost ratio.

Biaxially cube textured polycrystalline Cu(200) substrate tapes were produced for high temperature superconducting (HTS) coated conductor applications. A comparison is made between Cu substrates fabricated by reverse cold rolling followed by recrystallization, from stock materials that were obtained in the form of extruded rod and rolled plate. Detailed x-ray diffraction (XRD) studies and orientation imaging microscopy (OIM) were performed to measure the in-plane alignment, out-of-plane alignment, and microtexture at various deformation levels and annealing temperatures. The rod starting geometry proved to have superior biaxial alignment with a predominant (220) deformation texture after rolling. Phi (?) scan and psi (?) scan XRD reveals that the best in-plane and out-of-plane alignment, measured in terms of full width half maximum (FWHM) values of 5.4° and 5.8°, were obtained at 99.5% reduction in thickness and 750?°C annealing temperature. OIM microtexture results indicate that more than 97.5% of grains had less than 10° misorientation with no observable twinning.

This paper examines the operational effects of converting a 14-ft-wide curb lane to an 11-ft-wide travel lane with a 3-ft-wide undesignated lane at various locations in Broward County, Florida. Six midblock sites with various configurations were selected for study. Two of the midblock sites had previously been striped with the 3-ft undesignated lane, and these served as comparison sites. Videotapes were taken of bicyclists riding through the midblock and intersection locations before and after placement of the 3-ft undesignated lane striping. At the locations where the 3-ft stripe was already in place, the videotaping was done to examine whether changes were occurring over time. Software was used to extract images at all midblock locations so that before and after lateral spacing measurements could be obtained. After the new striping, (a) bicycles were ridden, on average, 7 to 9 in. further away from the gutter pan seam; (b) motor vehicles were driven, on average, 6 to 12 in. farther away from the gutter pan seam; (c) passing motor vehicles were driven, on average, 3 to 5 in. closer to bicycles at curb and gutter sites; conversely, passing motor vehicles were driven, on average, 4 to 5 in. farther away from bicycles at the sites where the stripe was already in place; and (d) the addition of the stripe at new locations had the effect of reducing the amount of motor vehicle encroachment into the adjacent lane on these multilane roadways.

The large‐scale monitoring and estimation of crop yield is essential for food security in Mexico. This study developed and validated a method of monitoring and estimating corn (Zea maysL.) yield by means of satellite and ground‐based data. In autumn–winter 1999 and spring–summer 2000, eight locations under irrigated and nonirrigated conditions in corn valleys of Mexico were localized by Global Positioning Systems (GPS) and were sampled every 15 d. Photosynthetic active radiation (PAR), leaf area index (LAI), crop development stage (DVS), planting dates, and grain yield data were gathered from the field. The normalized difference vegetation index (NDVI) was derived from NOAA‐Advanced Very High Resolution Radiometer (AVHRR) images. A growth model was developed to integrate satellite and ground data. Net primary productivity (NPP) was estimated using PAR and NDVI. Dry weight increase (kg ha−1d−1) was determined considering NPP and the partitioning factor. Results indicated that the model accounts for 89% of the variability in yields under irrigated conditions and 76% under nonirrigated conditions. The methodology seems advantageous in large‐scale monitoring and assessment of corn yield.

The Advanced Very High Resolution Radiometer (AVHRR) data acquired by the National Oceanic and Atmospheric Administration's (NOAA) satellites provide daily observations of the Earth's surface. While NOAA-14 data from ascending orbits are operationally used for global vegetation monitoring; NOAA-15 data from descending orbits could provide additional daily coverage. The normalized difference vegetation index (NDVI), derived from the solar reflective data, is linked to vegetation condition and plant biomass production on land surfaces. Because a single AVHRR scene is seldom completely cloud-free, maximum value compositing (MVC) of multi-date NDVI data is widely used to minimize cloud contamination. While ten-day composites from NOAA-14 AVHRR data may not be cloud-free; critical short-term changes in vegetation condition may be lost in composites created over longer time periods. AVHRR data of Texas obtained from NOAA-15 (morning satellite) and NOAA-14 (afternoon satellite) were used in our study on the potential benefits of merged morning and afternoon NDVI data sets for crop monitoring. A strong correlation was observed between NOAA-14 and NOAA-15 NDVI data derived from top-of-atmosphere (TOA) reflectance.

Mixed-ligand complexes [MX2(MBPY)] (M = PdIIor PtII; X = Cl−, I−, N−3or NO2−; MBPY = 4,4′-dimethyl-2,2′-bipyridine) have been prepared and characterised by elemental analyses, conductivity measurements, i.r., electronic absorption and 1H-n.m.r. spectroscopic techniques. The cyclic voltammograms of these complexes suggest the involvement of the metal dπ orbital in the one-electron oxidation process and the π* orbital of the MBPY in the one-electron reduction process. [Pt(MBPY)(N3)2] shows solution-state luminescence at room temperature.

In-vehicle navigation and route guidance systems have been proposed as solutions to the congestion problem. For these systems to be effective, drivers should be able to understand the information and respond in a safe manner. Some of the human factors issues associated with the design of these systems are discussed. The focus is on the safety and human factors issues while the person is driving on the road. The following issues are addressed in detail: mode of information presentation, information content and format, message timing, display location, and driver interaction with devices. Conclusions and areas for future research are also provided.

Abstract: A new approach for controlling microstructure development during hot working processes is proposed. This approach is based on optimal control theory and involves state-space type models for describing the material behavior and the mechanics of the process. The effect of process control parameters such as strain, strain rate, and temperature on important microstructural features can be systematically formulated and then solved as an optimal control problem. This method has been applied to the optimization of grain size and process parameters such as die geometry and ram velocity during the extrusion of plain carbon steel. Experimental results of this investigation show good agreement with those predicted in the design stage.

Different canopy characteristics of industrial eucalyptus may lead to differences in water evaporation and availability to plants. This study aims to understand rainfall partitioning in a young clonal plantation (age of 2–4.5 years) of three eucalyptus species by relating tree parameters: diameter at breast height, total height, and leaf area index. We measured rainfall, throughfall, stemflow and litter interception, along with the tree parameters. The eucalyptus trees had rainfall interception varying between 22 mm (for 178 mm of rainfall) and 42 mm (for 87 mm of te rainfall), throughfall between 106 mm (for 186 mm of rainfall) and 44 mm (for 74 mm of rainfall), and stemflow between 0.5 mm (for 92 mm of rainfall) and 1.4 mm (for 24 mm of rainfall). For the three species, rainfall interception varied between 12 and 48%, throughfall between 57 and 90%, and stemflow between 0.3 and 5.4%. The coefficient of determination between interception and rainfall was 0.76, indicating interception depends on other variables, possibly including antecedent rainfall, rainfall intensity, and seasonality. Interception decreased with a reduction in leaf area index caused by eucalyptus defoliation. The E. benthamii had 0.75 mm of throughfall per 1 mm of rainfall, whereas in E. dunnii and E. saligna, these ratios were 0.71 and 0.68, respectively. Stemflow in E. benthamii and E. dunii had a higher positive relationship with the diameter at breast height of the trees, whereas in E. salignathe highest relationship was with the rainfall. These results contribute to establishing management strategies, such as choosing suitable eucalyptus species to local climate, and to improve the synchronization of crop-demand versus soil-water-supply while maintaining streamflow to fulfill ecological and production needs.

Ecological and hydrological impacts are expected when watersheds are under commercial eucalyptus. In this study we evaluated event-based hydrology and sedimentation in paired watersheds under commercial eucalyptus and grasslands cover. Flow, suspended sediment concentration, and sediment production were measured and simulated with the Limburg Soil Erosion Model (LISEM) in paired hydrographic watersheds located in southern Brazil; one occupied with 7-years old Eucalyptus salignaplantation (forest watershed-FW; 0.83 km2) and another Pampa biome with native and exotic grasses used for beef cattle production (grassland watershed-GW; 1.10 km2). The effect of rainfall on hydrological and sedimentological variables was more evident in GW compared with FW. The shape of the hydrograph was steepest in GW, with rapid, marked increase and decrease in flow during rainfall. The parameters changed for model calibration in FW and GW were soil saturated hydraulic conductivity, initial soil moisture, and Manning roughness coefficient, whereby the statistical performance was classified as good (NSE> 0.75). Fourteen events different from those used in the calibration process were validated for FW and GW, with NSE index classified as “good” and “very good” for hydrology. Our study shows limitations of LISEM in calibrating and validating the sediment yield for individual events due to the spatial variability of factors controlling soil erosion. The validated modeling results of this study may be applied in simulating soil and crop scenarios in watersheds cultivated with commercial forest and grassland for grazing.

Fatigue performance of Inconel 718 (IN718) parts built using laser powder bed fusion (L-PBF) is often poorer than that of the cast and wrought alloy parts. This is because of detrimental effects arising from the microstructures such as brittle phases and anisotropy as well as porosities. To improve fatigue performance of L-PBF IN718, two types of post processes namely hot isostatic pressing (HIP) (performed at 980 °C, 100 MPa and 4 h) and shot peening (performed at 0.45 mmA intensity and 200 % coverage) were employed individually as well as sequentially on different specimens in addition to a standard processing route consisting of L-PBF build followed by solution annealing and double aging heat treatment. Porosities were considerably reduced by HIP-ing (from 0.39 % to 0.08 % porosity volume ratio) but this did not translate to improvements in fatigue performance. This can be attributed to the presence of inclusions and yield strength reduction resulting from γ” solutionisation. High compressive residual stresses of close to 1 GPa were recorded following shot peening regardless of whether HIP-ing was carried out prior to the shot peening. Improvement in fatigue lives particularly at high stress levels was observed on shot peened specimens without HIP-ing (H + SP) which can be explained by the compressive residual stresses that delay the onset of fatigue crack initiation. Shot peening applied on the HIP-ed specimens (H + HIP + SP) however, resulted in fatigue performance deterioration. This is related to the harmful tensile stresses that must exist alongside the compressive residual stresses in a shot peened surface, as evident from the location of the sub-surface crack initiations near the residual stress transition region approximately 300 μm from the free surface. In this case, detrimental effects arising from tensile stresses appear to have outweighed the benefits from compressive stresses on fatigue performance.

The article offers information on USLIMITS2, a Web-based application released by the U.S. Federal Highway Administration's (FHWA) Office of Safety in 2012. Created to help State and local departments in determining safe, reliable and logical speed limits, USLIMITS2 is an updated version produced by a research team led by the University of North Carolina Highway Safety Research Center. It also features case studies which highlight the use of USLIMIT2 in real-life situations.