Horizontal Curves Research Articles

Effect of emergency medical service response time on fatality risk of freeway crashes: Bayesian random parameters spatial logistic approach.

Emergency medical service (EMS) serves as a pivotal role in linking injured road users to hospitals via offering first aid measures and transportation. This paper aims to investigate the effect of emergency medical service (EMS) response time on the fatality risk of freeway crashes. Crash injury severity data from Kaiyang Freeway, China in 2014 and 2015 are employed for the empirical investigation. A Bayesian random parameters spatial logistic model is developed for analyzing crash severity. Bayesian inference of the random parameters spatial logistic model demonstrates the importance of reducing EMS response time on minimizing the fatality risk of freeway crashes. Fatality odds would increase by 2.6% for 1 min increase in EMS response time. Additionally, vehicle type, crash type, time of day, horizontal curvature, vertical grade, and precipitation are also found to have significant effects on the fatality probability of freeway crashes. It is crucial to reduce EMS response time to decrease the fatality likelihood of freeway crashes. Some countermeasures have been proposed to shorten EMS response time.

Influence of Curve Geometry Factors on Driver’s Speed Decision Making When Passing through a Horizontal Curve

Influence of Curve Geometry Factors on Driver’s Speed Decision Making When Passing through a Horizontal Curve

Strengthening of the railroad track for high-speed traffic on the Bukhara-Misken section

In the article the work of ballast prism and subgrade is considered, on the basis of analysis two-layer reinforcement from geotextile is offered, also strengthening by water-soluble polymer in conditions of sandy zone on high-speed sections of railroads is suggested. The principle of stationarity of the total potential energy of deformable Lagrangian systems is used to determine the stress-strain state of the earth bed. The dependences between the components of stress and strain tensors characterizing specific models of the medium have been established, and an elastic ground medium with no residual deformation from external load has been considered. And also offer designs of sleepers with concave surface, which will increase the service life and ensure the reliability of its operation on horizontal and vertical curves of railroads. A new fluoroplastic under-rail gasket, which does not change its characteristics during 5 years, contacting with the base of the rail, flat inner support surface, contacting with the sleeper, reduces load vibration from the rolling stock on the sections of high-speed traffic is offered.

Numerical and Experimental Investigation of the Influence of Backpressure on a Confined Impinging Jet for Small Nozzle-to-plate Spacing

In order to further extend understanding of the heat transfer characteristics under an enclosed area, the influence of backpressure on a single impingement jet with small nozzle-to-plate spacing (H/D) is studied. Particle image velocimetry (PIV) technique and a commercial fluid dynamics solver (CFD) are respectively employed to investigate the fluid dynamics of the impinging jet, with a Reynolds number (Re) of 3462–6125, at a small nozzle-to-plate spacing (H/D) of 0.25–1.25. Experimental data are in well agreement with numerical simulation data. The findings indicate that the H/D ratio significantly influences the formation of backpressure in the flow field. The backpressure then influences the boundary layer velocity on the impingement surface, in turn affecting the impingement surface's heat transfer characteristics. In addition, a turning point in the horizontal velocity curve of H/D = 0.4 is found for an entire range of jet heights, which is independent of the Reynolds number (Re).

Pemodelan Kondisi Geometrik Jalan Terhadap Potensi Kecelakaan Lalu Lintas

Road infrastructure has an impact on the occurrence of road traffic accidents. The geometry of a road is a variable that influences the occurrence of road traffic accidents. Interpreting the observed crashes into an equation that can describe the crashes is one of the most difficult problems faced by scientists and engineers in any research. The traffic accident research conducted is still limited to analyzing the causes of accidents and jumping to handling strategies that do not reveal how much geometric influence on accidents at the location. This research was developed using a comprehensive modeling approach to illustrate how highway geometric design, in this case the alignment, influences crash rates. This study aims to analyze the influence of road geometrics on the incidence of accidents. The method used is multiple liner regression measurement model using R-Studio. The variables to be studied include road geometry planning parameters, especially horizontal alignments which include stopping sight distance (X1), radius of horizontal curve (X2), shoulder width X3, and transition curve length (X4). The results of the study obtained a relationship in the mathematical equation Y = 99.55508-0.02634X1+1.17647X2-0.06999X3-0.03906X4 with the most significant correlation value produced is the transition curve length and radius of horizontal curve. Based on the multiple R-squareed value of 0.8775 this model has a very strong correlation category. Where the ability of X1 to X4 is able to explain Y by 80%.

Analysis and Modelling of Acceleration Behavior on the Horizontal Curves of Two-Lane Undivided Rural Highways Passing Through Mountainous Terrain

Analysis and Modelling of Acceleration Behavior on the Horizontal Curves of Two-Lane Undivided Rural Highways Passing Through Mountainous Terrain

Improving road safety at horizontal curves using V2I speed warning messages

Introduction: According to the Federal Highway Administration, a quarter of fatal collisions has occurred at horizontal curves. The average collision rate at horizontal curves was found to be three times higher than other types of highway segments. The lack of compliance with the speed limit and driver-related factors are among the main contributing factors to those collisions. Vehicle to Infrastructure (V2I) communications can address these limitations by providing drivers with valuable in-vehicle warning messages based on operational and safety data. There is limited effort investigating the impact of different types of V2I warning messages at horizontal curves and among different profiles of drivers. This study aims to thoroughly examine drivers’ behavior and compliance with different V2I warning messages when approaching horizontal curves. Methods: A driving simulator experiment and self-reported survey were conducted. Three main hypotheses were analyzed in this study. First, whether supplying drivers with in-vehicle V2I warning messages will positively affect drivers’ behavior at horizontal curves compared to the standard road signs. Second, whether there will be a significant difference in drivers’ behavior when receiving text and audio V2I warning messages. Third, whether seniors and female drivers will comply more with speed limit advisory provided through V2I message than younger and male drivers. Results: The Analysis of Covariance confirmed the first two hypotheses. Two main measures of drivers’ behavior found to be lower in the V2I communication scenarios compared to the base one. The audio warning message was found to be more promising in increasing drivers’ compliance with speed limit advisory when approaching the curves. Analyzing the third hypothesis revealed that younger and male drivers had higher curve initiation speed compared to females and seniors. Practical Applications: The findings of this study can be used by transportation researchers, authorities, and car manufacturers to improve the effectiveness of in-vehicle V2I warning messages among different profiles of drivers.

ANN deformation prediction model for deep foundation pit with considering the influence of rainfall

Deep foundation pits involving complex soil–water-structure interactions are often at a high risk of failure under heavy rainfall. Predicted deformation is an important index for early risk warning. In the study, an ANN model is proposed based on the Wave Transform (WT), Copula method, Convolutional Neural Network (CNN) and Long Short-Term Memory Neural Network (LSTM). The total deformation was firstly decomposed into low and high frequency components with WT. The CNN and LSTM were then used for prediction of the two components with rolling training and prediction. The input variables of the CNN and LSTM were determined and optimized based on the correlations analysis of Copula method of the two components with different random variables, especially with the rainfall. And finally, the predicted total deformation was obtained by adding the two prediction components. A deep foundation pit in Chengdu, China was taken as a case study, of which the horizontal deformation curves at different measuring points shows three types of developed trend, as unstable, less stable, and stable types. The predictions of the deformations of different development types by the proposed ANN model show high accuracies with a few input variables and can accurately prompt risk warning in advance.

Limited Response of Curve Safety Level to Friction Factor and Superelevation Variation under Repeated Traffic Loads

Although road horizontal curves are high-risk sections for accidents, current road safety assessments often neglect the dynamic evolution of superelevation and the friction factor. The connotation for road safety level was clarified by examining the significance of road factors in traffic safety through the systemic characteristics of roads. Among these characteristics, curve safety level is determined by the ratio of the supply and demand of the lateral friction factor. On the basis of international standards and specifications, this study clarified the design supply and demand of friction factors for curve by considering the distribution of tangential and lateral friction factors. Expanding on the steady-state bicycle model while accounting for road geometric parameters and vehicle operation characteristics, the lateral friction factor demanded for vehicles was quantified. Meanwhile, the characteristics of the friction factor supplied and the superelevation variation were analyzed by using the road service life as a variable, along with their influence on the actual supply of the friction factor and the curve safety level. The results of the analysis indicate a rapid decrease in curve safety level during the first two years of road utilization, followed by a slower declining trend, with a significant 27% reduction in curve safety level by the end of the second year. Furthermore, the decline in the curve safety level is mainly attributed to variations in the road surface friction factor, whereas the influence of superelevation variation on the curve safety level is restricted. In the absence of maintenance interventions, the curve safety level will decrease by over 30% after three years of operation. Controlling operational speed is one of the effective measures for ensuring traffic safety. Meanwhile, the impact of the friction factor and the superelevation variation on the curve safety level accumulates over time, thus causing drivers to have difficulty perceiving these alterations. Therefore, dynamic safety evaluations that account for the fluctuation in the friction factor and superelevation induced by repetitive vehicle loading must be undertaken.

A methodological procedure for evaluating curve-related misclassifications in motor vehicle crash databases

Motor vehicle crashes have been identified as a leading cause of death all over the world. To better promote traffic safety and protect lives of the traveling public, transportation agencies develop crash databases to effectively manage reportable motor vehicle crashes. Crash reports from law enforcement authorities usually serve as the primary source for motor vehicle crash data. However, unintentional errors in law enforcement crash reports, errors in state-maintained crash databases, and the migration and rearrangement of data could introduce problems of data consistency in crash databases. One such identified data inconsistency is regarding horizontal curves. It can result in misidentifications of curve-related crashes, which can affect safety analysis using these data. This is significant since many studies have related horizontal curves to crash frequency and severity. To solve this problem, this study proposed a methodological procedure for evaluating (i.e., identifying, classifying, and quantifying) curve-related misclassifications in crash databases. The applicability of the proposed methodological procedure was illustrated through a case study using the Crash Records Information System (CRIS) maintained by the Texas Department of Transportation (TxDOT). The results indicated that transportation agencies could employ the proposed methodological procedure to evaluate inconsistencies associated with curve-related crash data both effectively and efficiently.

A Case Study on the Effect of Geometric Design Consistency on Road Crashes on Narayanghat-Muglin Road Section

Design consistency is overlooked while designing roads, resulting in unsafe road facilities. The safety performance of a highway can be greatly enhanced by detecting and addressing any inconsistencies present on the road. Over time, the application of geometric standards shifted from new road construction to upgrading, which could result in limited design options. Due to the emerging importance of design consistency in geometric design, this research has been initiated to evaluate horizontal curve consistency based on an established operating speed prediction model.
 Horizontal curve data of the Narayanghat–Mugling Road section has been collected from the Division Road Office, Bharatpur, and accident data has been obtained from the District Traffic Police, Chitwan. Out of 242 horizontal curves in the Narayanghat-Muglin road section, the design consistency of 223 horizontal curves was evaluated, while 19 horizontal curves with posted speed limits were not considered because these curves are not within the range of design criteria set out in Asian Highways Design Standards (1993).
 The average, maximum, and minimum 85th percentile speed was found to be 78, 101, and 32 kmph respectively. Out of 223 horizontal curves evaluated for individual consistency based on operating speed, 75% of the curves were categorized as “poor”, 16% as “fair”, and 9% as “good”. It was found that under successive element consistency evaluation based on operating speed, 22% of horizontal curves were categorized as “poor”, 23% as “fair”, and 55% as “good”. When studied under vehicle stability consistency evaluation criteria, 88% of the curves were classified as “fair” and 12% as “good”. It was found that the predicted accidents caused by geometric design inconsistency and vehicle stability are 5.12% of total accidents per year.
 From the safety standpoint, if the condition |V85-Vd|>20 is met, critical discrepancies between the design speed and operating speed arise, resulting in unsafe operations. Therefore, it is generally advisable to consider redesigning those road sections.

Safety impact of highway geometrics and pavement parameters on crashes along mountainous roads

Having the capability of estimating both the number of crashes and their severity levels, crash prediction models are a precious tool in highway safety. However, there hasn't been any research on predicting traffic crashes on Indian mountainous rural highways. The primary objective of this research is to develop safety performance functions (SPFs) for traffic crashes occurring on rural roads located in the mountainous region of Uttarakhand, India.For analysis, the study utilized five years of crash data collected from different types of rural roads. The road network was divided into constant segments of 500m each, and separate models were developed for single (TSVC) and multi-vehicle (TMVC) crashes using the negative binomial regression approach. These SPFs highlight important significant variables in terms of positive and negative association and a potential change in subject crash frequencies. The results concluded that different types of risk factors impact both types of crashes, with horizontal (HC) and vertical curves (VC) in common. For instance, spot speed increases TSVC crashes by 3.87 %, whereas HC and VC tend to increase subject crashes by 8.32 % and 29.95 %, respectively.Similarly, TMVC is influenced by carriageway (CW) and shoulder width (SW). The result proposed that an increase in CW and SW can decrease frequencies by 0.668 times and 0.819, respectively. Additionally, the model highlighted the importance of rut-depth and the presence of pavement markings in the road safety analysis. At last, further research scope is suggested based on the limitations of this study.

Optimal eco-driving scheme for reducing energy consumption and carbon emissions on curved roads

Energy consumption and emissions of a vehicle are highly influenced by road contexts and driving behavior. Especially, driving on horizontal curves often necessitates a driver to brake and accelerate, which causes additional fuel consumption and emissions. This paper proposes a novel optimal ecological (eco) driving scheme (EDS) using nonlinear model predictive control (MPC) considering various road contexts, i.e., curvatures and surface conditions. Firstly, a nonlinear optimization problem is formulated considering a suitable prediction horizon and an objective function based on factors affecting fuel consumption, emissions, and driving safety. Secondly, the EDS dynamically computes the optimal velocity trajectory for the host vehicle considering its dynamics model, the state of the preceding vehicle, and information of road contexts that reduces fuel consumption and carbon emissions. Finally, we analyze the effect of different penetration rates of the EDS on overall traffic performance. The effectiveness of the proposed scheme is demonstrated using microscopic traffic simulations under dense and mixed traffic environment, and it is found that the proposed EDS substantially reduces the fuel consumption and carbon emissions of the host vehicle compared to the traditional (human-based) driving system (TDS), while ensuring driving safety. The proposed scheme can be employed as an advanced driver assistance system (ADAS) for semi-autonomous vehicles.

Safety performance analysis of horizontal curves in urban areas

While numerous studies have examined horizontal curve risk factors in rural areas, there is only one study for urban areas. Moreover, previous studies have used limited datasets, which tend to generate an intrinsic bias on results either by the sample size or due to a lack of understanding of all the risk factors associated with curve safety.This study aims to narrow this knowledge gap in three aspects: it focuses on urban areas; it uses a large novel GIS dataset of about 25,000 urban curves; and it expands the traditional curve risk factor pool by examining the spatial relationship of curves to adjacent curves and intersections. Using this curve dataset and six years of statewide fatal and injury crash data in the state of Florida, the study develops customized safety performance functions (SPFs) for urban curves based on different spatial relationships of curves to intersections.The results confirm that the traditional risk factors for rural curves, such as traffic volume, curve radius and length, speed limit, functional classification, and the number of lanes, also apply to curves in urban areas. However, the new finding is that curve safety in urban areas is affected by the proximity of curves to adjacent curves and intersections. The curves with intersections and isolated curves (with no adjacent nearby curves) are at high risk. There are also risk factor differences between single and dual-centerline roads. We also observed differences between the travel directions on divided roadway curves, but these differences will require more research.

Three-Dimensional Profiling of Drilled Shafts Based on Four-Point Ultrasonic Measurement

Drilled piles are one of the most important foundation systems, and the shapes of the shafts prior to casting have a significant impact on their quality. In order to better obtain geometrical information on the shafts, this study proposes a profiling approach based on four-point ultrasonic measurement. First, data from horizontal sections are fitted using least squares to obtain sectional contour curves. Vertical contours are generated by iterative fitting to ensure the smoothness of the curves. Data-processing software is then used to merge the horizontal sectional curves and the vertical curves into a three-dimensional image that approximates the actual contours of the shaft.

The impact of the combination equilibrium of horizontal and sag-vertical curves on safety

The impact of the combination equilibrium of horizontal and sag-vertical curves on safety

Influence of coupling vertical and lateral loads on the centre negative flexural behaviour of prestressed monoblock concrete sleepers

At horizontal railway curves, the track is frequently subject to coinciding vertical and lateral wheel loads, which in some cases could be of high intensity. Currently, the influence of such loading pattern on the centre negative flexural response of prestressed monoblock concrete sleepers (PMCS) is not clearly analysed. As a result, the current codes of practice provide limited guidance pertinent to the design of PMCS under this loading condition. To address these issues, finite element models were accomplished and rigorously verified against analytical and experimental studies existing in the literature. The noteworthiness of the numerical findings, based on the considered loading scenarios, is that the presence of lateral load could increase the flexural stress at the top fibre of midspan sections by 223% compared to the influence of vertical load alone. Based on the numerical outputs, an equation has been proposed to quantify the increased flexural stress of PMCS due to lateral load, and further studies are recommended to complement the results expressed in this research.

Relationship between Horizontal Curve Geometry and Single-Vehicle Crash Occurrence on Rural Secondary Highways

Single-vehicle crashes are overrepresented on rural two-lane highway curves. While prior work investigated the relationship between crash occurrence and aggregate curve characteristics, several important aspects related to curve geometry remain uninvestigated. To this end, research was undertaken to evaluate the safety effects associated with several specific horizontal curve-related geometric characteristics (including curve type, curve direction, tangent distance between curves, and curve design speed) on rural two-lane undivided highways, considering non-animal single-vehicle crashes. Eight years of crash data were obtained for 277 mi and 557 mi of curved state and county highway segments, respectively, within Michigan. Several mixed-effects negative binomial models, with county- and site-specific random intercepts, were developed separately for state and county highways. The model results indicated that several key geometric factors were associated with crash occurrence on rural two-lane highways, including curve type, curve direction, tangent distance approaching the curve, inner-curve tangent distance, and curve design speed. Each of the following geometric characteristics was associated with elevated single-vehicle crash occurrence: (1) compound and reverse curves (compared with simple curves); (2) left-turning curves (compared with right-turning); (3) curves with design speeds lower than the speed limit (compared with curves with higher design speeds); (4) longer tangent distances approaching a simple curve or the initial curve in a series; and (5) shorter inner-curve distances between successive compound or reverse curves. Compound or reverse curves should be avoided in favor of simple curves with an elongated inner-curve distance. Enhanced warning signage should be considered where such curve designs cannot be avoided.

Determining 3D coordinates based on the track geometry description

This paper is focused on the data description of the railway infrastructure. Its aim is to present the possibilities of constructing of linear elements representing tracks in 2D and their subsequent transformation into 3D using the parametric description of horizontal and vertical curves. The transformation is based on determining the spatial coordinates of the newly emerging 3D linear elements. This process is supposed to be implemented in such a graphical editor environment that allows the relevant data to be transferred to the the database based on the Multipurpose Railway Infrastructure Model. With the use of this data, it is possible to perform, among other things, the visualization of the railway infrastructure.

Synthetic Drivers’ Performance Measures Related to Vehicle Dynamics to Control Road Safety in Curves

The road alignment design relies on the knowledge of vehicle dynamics variables. However, it assumes that drivers faithfully follow the lane axis on straights and curves. Deviating from this assumption leads to unexpected outcomes and can significantly impact users’ safety. In this context, vehicle speed and longitudinal acceleration play a crucial role as key references in the international standards. They provide insights into critical driving aspects; therefore, it is essential to thoroughly analyze their real trends. Broad data collection campaigns should derive synthetic indicators in order to highlight eventual significant deviations between the ideal and real dynamics. To achieve this objective, the authors propose some indexes deduced during an experimental study with a Sim-Easy driving simulator, by AVSimulation. Importantly, these indicators can be freely applied in real driving scenarios without limitations. These indexes were tested on four different horizontal curves and proved effective in identifying relevant characteristics related to longitudinal acceleration and speed. Looking ahead, by analyzing similar data for numerous driving contexts on real roads, infrastructure managers could use this methodology to identify those sections with increased vulnerability for users’ safety. Moreover, the collected data from sensors, processed using these indicators, can be filtered and transmitted to users (via ADAS tools) while driving on a specific road to provide timely warnings about potential difficulties. The indicators control the physical variable (acceleration or speed) on a certain geometric element with reference to what is prescribed by the standard. For example, the acceleration indicators are normalized with respect to a threshold value while for speed indexes, the result depends on the difference between the end control points of the geometrical element. In both cases, international regulations report prescribed or recommended reference values, so the analyst is immediately aware of any critical issues in the maneuver.