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Journal articles on the topic 'Horizontal Curve'
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1
You, Qing Chong, and Said M. Easa. "Roadside-curve lateral offsets for roadway reverse horizontal curves with intermediate tangents." Canadian Journal of Civil Engineering 47, no. 4 (April 2020): 382–94. http://dx.doi.org/10.1139/cjce-2018-0547.
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Following the roadside design curve of a spiraled roadside curve (SRC) previously proposed by the authors, this paper examines the characteristics of the required lateral offset ratios defined by the SRC on roadway reverse horizontal curves, including two reverse spiraled horizontal curves with and without an intermediate tangent. The radius ratio of two reverse simply horizontal curves, the spiral curve lengths of two reverse spiraled horizontal curves, and the intermediate tangent length were found to be the major influential factors of the offset ratios. A complete set of design tables was developed for reverse simple horizontal curves and reverse spiraled horizontal curves respectively, which would have significant engineering implications to roadside design of roadway reverse horizontal curves.
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Hasan, Moudud, Tarek Sayed, and Yasser Hassan. "Influence of vertical alignment on horizontal curve perception: effect of spirals and position of vertical curve." Canadian Journal of Civil Engineering 32, no. 1 (February 1, 2005): 204–12. http://dx.doi.org/10.1139/l04-090.
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Several studies have shown that the perception of horizontal curves can be influenced by an overlapping vertical alignment. A previous two-phase study investigated the hypothesis that a horizontal curve appears flatter when overlapping with a vertical sag curve and sharper when overlapping with a vertical crest curve. The study concluded that the hypothesis was valid. The study also developed several statistical models to estimate the perceived radius of horizontal curves in a combined alignment. This study extends the earlier work by investigating the effect of additional geometric parameters on the perception. The parameters examined include the presence of spiral curves, the length of the spirals, and the position of the vertical curve midpoint relative to the horizontal curve. It was found that (1) driver misperception of the horizontal curvature increases as the radius of the horizontal curve increases, (2) the presence of a spiral curve affects driver perception of the horizontal curvature in the case of crest combination only, (3) the length of the spiral curve has no effect on the perception whether on crest or sag combinations, and (4) while the effect of the position of the vertical curve midpoint relative to the horizontal curve is not statistically significant, it seems that the perception problem appears to diminish as the positive offsets increases.Key words: highway geometric design, visual perception, combined alignment.
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Said, Dalia, Yasser Hassan, and A. O. Abd El Halim. "Comfort thresholds for horizontal curve design." Canadian Journal of Civil Engineering 36, no. 9 (September 2009): 1391–402. http://dx.doi.org/10.1139/l09-075.
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A key to better geometric design of highways is designing horizontal curves conforming to driver behaviour. The values of side friction factors in the point mass formula, used for the design of the minimum radius of a horizontal curve, are based on the upper threshold of driver comfort. In the current guidelines, these driver comfort levels were established in research work carried out back in the 1930s. Recently, it was found that faster drivers tend to accept higher comfort thresholds to maintain their speed and minimize speed reduction between curve and tangent. An experiment was designed at Carleton University to collect newer data on driver behaviour including speed and lateral acceleration. The results confirmed the need to revise the values of side friction demand especially for sharp curves. In addition, a model was developed to determine the side friction factor to be used in design or in consistency evaluation of horizontal curves on rural roads and ramps.
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Bonneson, James. "Controls for Horizontal Curve Design." Transportation Research Record: Journal of the Transportation Research Board 1751, no. 1 (January 2001): 82–89. http://dx.doi.org/10.3141/1751-10.
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He, Jiao Long, Shu Guang Chen, and Xin Sheng Zhang. "Research on Technology of Highway Curve and Slope Road Segment Alignment Safety Design." Applied Mechanics and Materials 204-208 (October 2012): 1665–68. http://dx.doi.org/10.4028/www.scientific.net/amm.204-208.1665.
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In the paper, Combination curved with slope road segment on the driving experiment , The paper is analyzed the curve and slope road segment on Gradient, Horizontal Curve Radius, Speed and heart rate these variables of the inherent relation and law. The model of the relationship of the longitudinal slope and horizontal curve radius and heart rate is set up. By employing regression analysis, Conduct quantitative analysis, calculation and can be determined by the minimum horizontal curve radius value of vertical slope corresponding to at different vehicle-speeds on curved with longitudinal slope,Theoretical reference is provided for designers in the design technology research.
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Himes, Scott, Richard J. Porter, Ian Hamilton, and Eric Donnell. "Safety Evaluation of Geometric Design Criteria: Horizontal Curve Radius and Side Friction Demand on Rural, Two-Lane Highways." Transportation Research Record: Journal of the Transportation Research Board 2673, no. 3 (March 2019): 516–25. http://dx.doi.org/10.1177/0361198119835514.
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AASHTO’s A Policy on Geometric Design of Highways and Streets, 6th Edition, provides design criteria for horizontal curve elements based on the point-mass model. The model equates the centripetal force needed to navigate a horizontal curve of a specific radius traveling at the design speed to the combination of superelevation rate and side friction needed to achieve that force. Few researchers have examined the safety impacts of horizontal curve radius, superelevation rate, and design speed through crash-based research. None of the research reviewed included the effects of design speed or superelevation rate in the crash modification factors (CMFs) or functions. This research explored these factors using a negative binomial regression modeling approach based on data collected from the SHRP 2 RID 2.0 for 889 horizontal curves on rural two-lane highways in Indiana and Pennsylvania, which resulted in roadway departure crash modification functions for horizontal curve radius and side friction demand. The crash modification function for side friction demand includes an interactive component of horizontal curve radius and speed and a direct effect of superelevation rate on roadway departure crashes. The results showed that roadway departure crashes are expected to increase for decreasing curve radius, increasing posted speed limit, and decreased superelevation rate. Furthermore, curve-related CMFs were sensitive to the curve radii used in their development. CMFs developed from curves with larger radii tended to result in larger CMFs. Sample applications are provided for computing the effects of changing the horizontal curve radius, posted speed limit, or both on proposed alternatives.
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Lemonakis, Panagiotis. "Investigation of Motorcycle Trajectories in 2-lane Horizontal Curves." WSEAS TRANSACTIONS ON SYSTEMS AND CONTROL 16 (December 1, 2021): 610–25. http://dx.doi.org/10.37394/23203.2021.16.57.
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Most of the road design guidelines assume that the vehicles traverse a trajectory that coincides with the midline of the traffic lane. Based on this assumption the thresholds of various features are determined such as the maximum permissible side friction factor. It is therefore important to investigate the extent to which the trajectory of the vehicles is similar to the horizontal alignment of the road or substantial differences exist. To this end, a naturalistic riding study was designed and executed with the use of an instrumented motorcycle which measured the position of the motorcycle with great accuracy in a rural 2-lane road segment. The derived trajectories were then plotted against the horizontal alignment of the road and compared with the 3 consecutive elements which form a typical horizontal curve i.e., the entering spiral curve, the circular curve, and the exiting spiral curve. Linear equations were developed which correlate the traveled curvatures with the distance of each horizontal curve along the road segment under investigation. The process of the data revealed that the riders differ their trajectory compared to the alignment of the road. However, in small radius horizontal curves is more likely to observe curvatures that are similar to the geometric one. Moreover, the riders perform more abrupt maneuvres in the first part of the horizontal curves while they straighten the handlebars of the motorcycle before the end of the curve. The present paper aims to shed light on the behavior of motorcycle riders on horizontal curves and hence to contribute to the reduction of motorcycle accidents, particularly the single-vehicle ones.
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Fitzpatrick, Kay, C. Brian Shamburger, Raymond A. Krammes, and Daniel B. Fambro. "Operating Speed on Suburban Arterial Curves." Transportation Research Record: Journal of the Transportation Research Board 1579, no. 1 (January 1997): 89–96. http://dx.doi.org/10.3141/1579-11.
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Free-flow speeds were collected at both a control section and a curve section at 14 surburban sites with horizontal curves and 10 suburban sites with vertical curves. The scatter plots of the 85th percentile speed versus approach density indicate that when the approach density is between 3 and 15 approaches per km, approach density does not influence speed. Regression analysis indicated that the curve radius for horizontal curves and the inferred design speed for vertical curves can be used to predict the 85th percentile speed on curves for vehicles on the outside lane of a four-lane divided suburban arterial. For horizontal-curve sites, a curvilinear relationship exists between curve radius and the 85th percentile speed. A linear relationship provided the best fit between the inferred design speed and the 85th percentile speed for the vertical curve sites. For the horizontal and vertical curve sites, the speed at which 85th percentile speed becomes less than the inferred design speed is lower for suburban arterials than for rural highways. Drivers on suburban horizontal curves operate at speeds greater than the inferred design speed for curves designed for speeds of 70 kph or less, whereas on rural, two-lane roadways, drivers operate at speeds greater than the inferred design speed for curves designed for speeds of 90 kph or less. For vertical curves, the speeds at which drivers operate greater than the inferred design speed are 90 kph for suburban arterials and 105 kph for rural highways. These results are within 12 kph of the observed 85th percentile speeds on nearby control sections (approximately 80 kph for suburban arterials and 100 kph on rural highways).
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Qin, Jiazheng, Shiqing Cheng, Youwei He, Dingyi Li, Jia Zhang, Dong Feng, and Haiyang Yu. "Rate Decline Analysis for Horizontal Wells with Multiple Sections." Geofluids 2018 (November 19, 2018): 1–9. http://dx.doi.org/10.1155/2018/2047365.
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The widely used application of horizontal well makes it significant to effectively evaluate rate performance of horizontal well in oil and gas reservoir. However, most models in previous work only focus on rate decline analysis (RDA) of horizontal well with single section (HWSS); they hardly address the problem that production rate distributes nonuniformly along horizontal wellbore in analyzing rate transient behaviors. However, only some horizontal segments contribute to the total production rates, and the production of each section along horizontal wellbore is not the same in fact, which may be caused by reservoir heterogeneity, selective completion, and nonuniform formation damage along horizontal wellbore. Therefore, the effect of these phenomena on rate decline characteristics cannot be ignored. The aim of this paper is to propose an analytical model to investigate transient rate response of a horizontal well with multiple sections (HWMS). The compound type curves, including the normalized production curve, the normalized production integral curve, and the production integral derivative curve, are developed to distinguish the different cases. The influences of some sensitive parameters on decline curves are further discussed. Results show obvious differences on the decline curves between the HWMS and HWSS. The parameters are sensitive on decline curves, which explore the feasible application on production performance evaluation and parameters interpretation through history matching the production data with the compound type curves in this paper.
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Himes, Scott, and Eric Donnell. "Safety Effects of Horizontal Curve Reliability Index." Transportation Research Record: Journal of the Transportation Research Board 2674, no. 9 (July 12, 2020): 627–36. http://dx.doi.org/10.1177/0361198120930715.
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Recent advancements in analytical processes have used probabilistic approaches to examine the efficacy of the point mass model (and other Green Book models) to develop reliability-based approaches for geometric design. However, there has been minimal research establishing the link between reliability measures and substantive safety (expressed through crash frequency). The objective of this paper is to use empirical data supporting the calculation of reliability index for existing horizontal curves and to estimate the relationship between reliability index and crash frequency. Other horizontal curve-related characteristics that may have an impact on crash frequency on horizontal curves for rural two-lane highways and rural freeway facilities are controlled for in the evaluation. The safety analysis showed that the wet pavement reliability index was significantly associated with crash frequency for total curve-related crashes, single-vehicle run-off-road crashes, rollover crashes, truck-related crashes, and weather-related crashes. The relationship was strongest for the reliability index in its continuous form, meaning that the effect is continuous across the range of wet pavement reliability that was observed.
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Ryan, Alyssa, Emily Hennessy, Chengbo Ai, Wooseong Kwon, Cole Fitzpatrick, and Michael Knodler. "Driver performance at horizontal curves: bridging critical research gaps to increase safety." Traffic Safety Research 3 (October 19, 2022): 000014. http://dx.doi.org/10.55329/lmji8901.
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Horizontal curve segments are locations of critical safety concern given their high crash rates. Extensive research has identified that behavioral factors influence the occurrence of such crashes. However, the most beneficial countermeasure for a curve is not always implemented or is implemented inefficiently due to a lack of full understanding of driver behavior at curves compared to tangent roadway segments. The aim of this research is to identify the conditions that impact safety at curve locations compared to tangent segment locations. This is completed through a literature review of current research relating to curve safety issues and a safety analysis of curve and tangent segment data using a novel dataset that includes curve data throughout a region. The results of this study revealed several factors that cause horizontal curves to have a higher crash rate related to driver performance, including the increased task load and demand required at curve segments compared to tangent segments, and that horizontal curve segments have an increased rate of crashes per mile with an increasing AADT compared to tangent segments. Further, horizontal curve segments along one-way operations are of increased safety concern for drivers compared to tangent segments and two-way operations. The results of this study present the conditions that can be more carefully considered in future studies and analyses to consider the human factor cause behind the increased safety issue at curve segments.
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Gattis, J. L., B. Finley Vinson, and Lynette K. Duncan. "Low-Speed Horizontal Curve Friction Factors." Journal of Transportation Engineering 131, no. 2 (February 2005): 112–19. http://dx.doi.org/10.1061/(asce)0733-947x(2005)131:2(112).
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Himes, Scott C., and Eric T. Donnell. "Reliability Approach to Horizontal Curve Design." Transportation Research Record: Journal of the Transportation Research Board 2436, no. 1 (January 2014): 51–59. http://dx.doi.org/10.3141/2436-06.
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Felipe, Emmanuel, and Francis Navin. "Automobiles on Horizontal Curves: Experiments and Observations." Transportation Research Record: Journal of the Transportation Research Board 1628, no. 1 (January 1998): 50–56. http://dx.doi.org/10.3141/1628-07.
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Statistical information on the basic variables involved in driving through a horizontal curve was obtained using a 4×4 Latin square design experiment to measure the action of automobile drivers in test track horizontal curves. The independent variables used in the test curves were speed (comfortable, fast); pavement surface (dry, wet); driver (male, female); and curve radius (16 m, 26 m, 60 m, 100 m). The measured output was the driver’s selected speed and corresponding lateral acceleration. In addition, the passengers indicated their comfort level on a four-point semantic scale. Expert drivers also drove the test curves to establish the upper limits of the driver-vehicle-tire system. Field observations of four curves along a two-lane rural mountain highway measured driver vehicle speed, lateral acceleration, and lateral position. The results indicate that, for a comfortable ride, drivers are limited by their comfortable lateral acceleration on small radius curves and seek the “environmental speed” on large radius curves.
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Šeporaitis, Mindaugas, Viktoras Vorobjovas, and Audrius Vaitkus. "Evaluation of Horizontal Curve Radius Effect on Driving Speed in Two Lane Rural Road. Pilot Study." Baltic Journal of Road and Bridge Engineering 15, no. 4 (September 28, 2020): 252–70. http://dx.doi.org/10.7250/bjrbe.2020-15.503.
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This paper presents a case study of driving speed at horizontal curves in the regional road. The literature review of operating speed at horizontal curves in regional roads expresses the difference between design speed and driving speed. Driving speed was measured in ten horizontal curves on regional road No. 2610. Collected data was compared to the design speed, various design standards, and Operating Speed Prediction Models for traffic in low-volume roads. Based on result analysis, was proposed initial adjusted minimum radius of the horizontal curve based on operating speed. It is justified that proposed corrections based on operating speed ensure a credible speed limit effect on road safety. The performed experiment showed different tendencies comparing measured driving speed with permitted and design speeds. It was determined that dependent on specific curved section drivers tend to exceed posted speed limit from 17% to 98% of cases, and from 41% to 100% − the design speed in the horizontal curve. This research led to identifying the limitations of experimental research methodology. These limitations are related to experimental Site selection with different combinations of alignment elements, traffic, and accident data. A pilot study showed significant results and gave essential insights into the full-scale research plan. The results are expected to benefit both other researchers and the organisations responsible for the development and implementation of normative technical documents for road design.
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You, Qing Chong, and Said M. Easa. "Innovative Roadside Design Curve of Lateral Clearance: Roadway Spiraled Horizontal Curves." Journal of Transportation Engineering, Part A: Systems 143, no. 8 (August 2017): 04017031. http://dx.doi.org/10.1061/jtepbs.0000046.
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You, Qing Chong, and Said M. Easa. "Innovative roadside design curve of lateral clearance: Roadway reverse horizontal curves." Journal of Traffic and Transportation Engineering (English Edition) 5, no. 4 (August 2018): 268–83. http://dx.doi.org/10.1016/j.jtte.2017.09.004.
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You, Qing Chong, and Said M. Easa. "Innovative Roadside Design Curve of Lateral Clearance: Roadway Simple Horizontal Curves." Journal of Transportation Engineering 142, no. 11 (November 2016): 04016055. http://dx.doi.org/10.1061/(asce)te.1943-5436.0000889.
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Sil, Gourab, Avijit Maji, Suresh Nama, and Akhilesh Kumar Maurya. "OPERATING SPEED PREDICTION MODEL AS A TOOL FOR CONSISTENCY BASED GEOMETRIC DESIGN OF FOUR-LANE DIVIDED HIGHWAYS." Transport 34, no. 4 (July 17, 2019): 425–36. http://dx.doi.org/10.3846/transport.2019.10715.
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Researchers have studied two-lane rural highways to predict the operating speed on horizontal curves and correlated it with safety. However, the driving characteristics of four-lane-divided highways are different. Weak lane discipline is observed in these facilities, which influences vehicle speed in adjacent lane or space. So, irrespective of its lane or lateral position, vehicles in four-lane divided highways are considered free flowing only when it maintains the minimum threshold headway from any lead vehicle. Examination of two conditions is proposed to ensure the free flow. Vehicles meeting both conditions, when tracked from the preceding tangent section till the centre of the horizontal curve, are considered as free flowing. The speed data of such free flowing passenger cars at the centre of eighteen horizontal curves on four-lane divided highways is analysed to develop a linear operating speed prediction model. The developed model depends on curve radius and preceding tangent length. The operating speed of passenger car in four-lane divided highways is influenced by horizontal curve of radius 360 m or less. Further, longer tangent would yield higher operating speed at the centre of the curve. Finally, two nomograms are suggested for conventional design, consistency based design and geometric design consistency evaluation of four-lane divided horizontal curves.
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Xu, Guilong, Jinliang Xu, Chao Gao, Rishuang Sun, Huagang Shan, Yongji Ma, and Jinsong Ran. "A Novel Safety Assessment Framework for Pavement Friction Evolution Due to Traffic on Horizontal Curves." Sustainability 14, no. 17 (August 28, 2022): 10714. http://dx.doi.org/10.3390/su141710714.
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The friction coefficient is one of the dominant parameters affecting vehicle driving stability on horizontal curves. However, there is no comprehensive framework to assess the traffic safety on the horizontal curve with the evolution of the friction coefficient caused by the traffic flow. In light of this, this paper developed an integrated risk-assessment framework to evaluate the safety on the horizontal curve with the friction coefficient evolving under different traffic characteristics. The speed distribution on the horizontal curve of the freeway is obtained through field experiments that serve as the basic parameters of the model. A new multi-vehicle risk index (MRI) is introduced to assess the traffic safety risk for the horizontal curve by coupling the reliability theory and negative binomial. Three traffic characteristics are considered in the analysis: cumulative traffic volume (CTV), annual average daily traffic (AADT), and average daily traffic of heavy goods vehicles (AADTHGV). The results show that the AADT and AADTHGV have a considerable impact on the road risk level. When the truck traffic volume is less than 1000 veh/d, the risk of horizontal curves changes less as road operational time goes. The research results can provide a reference for the road maintenance department to determine the timing of road maintenance.
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Hassan, Yasser, Said M. Easa, and A. O. Abd El Halim. "Analytical Model for Sight Distance Analysis on Three-Dimensional Highway Alignments." Transportation Research Record: Journal of the Transportation Research Board 1523, no. 1 (January 1996): 1–10. http://dx.doi.org/10.1177/0361198196152300101.
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Existing sight distance models are applicable only to two-dimensional (2-D) separate horizontal and vertical alignments or simple elements of these separate alignments (vertical curve, horizontal curve). A new model is presented for determining the available sight distance on 3-D combined horizontal and vertical alignments. The model is based on the curved parametric elements that have been used in the finite element method. The elements presented are rectangular (4-node, 6-node, and 8-node elements) and triangular. These elements are used to represent various features of the highway surface and sight obstructions, including tangents (grades), horizontal curves, vertical curves, traveled lanes, shoulders, side slopes, cross slopes, superelevation, lateral obstructions, and overpasses. The available sight distance is found analytically by examining the intersection between the sight line and the elements representing the highway surface and the sight obstructions. Application of the new model is illustrated using numerical examples, and the results show that existing 2-D models may underestimate or overestimate the available sight distance. The proposed model should be valuable in establishing design standards and guidelines for 3-D highway alignments and determining the effect of various highway features on sight distance.
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Gülci, Sercan, Hafiz Hulusi Acar, Abdullah E. Akay, and Neşe Gülci. "Evaluation of Automatic Prediction of Small Horizontal Curve Attributes of Mountain Roads in GIS Environments." ISPRS International Journal of Geo-Information 11, no. 11 (November 9, 2022): 560. http://dx.doi.org/10.3390/ijgi11110560.
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Road curve attributes can be determined by using Geographic Information System (GIS) to be used in road vehicle traffic safety and planning studies. This study involves analyzing the GIS-based estimation accuracy in the length, radius and the number of small horizontal road curves on a two-lane rural road and a forest road. The prediction success of horizontal curve attributes was investigated using digitized raw and generalized/simplified road segments. Two different roads were examined, involving 20 test groups and two control groups, using 22 datasets obtained from digitized and surveyed roads based on satellite imagery, GIS estimates, and field measurements. Confusion matrix tables were also used to evaluate the prediction accuracy of horizontal curve geometry. F-score, Mathews Correlation Coefficient, Bookmaker Informedness and Balanced Accuracy were used to investigate the performance of test groups. The Kruskal–Wallis test was used to analyze the statistical relationships between the data. Compared to the Bezier generalization algorithm, the Douglas–Peucker algorithm showed the most accurate horizontal curve predictions at generalization tolerances of 0.8 m and 1 m. The results show that the generalization tolerance level contributes to the prediction accuracy of the number, curve radius, and length of the horizontal curves, which vary with the tolerance value. Thus, this study underlined the importance of calculating generalizations and tolerances following a manual road digitization.
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Collins, Kent M., and Raymond A. Krammes. "Preliminary Validation of a Speed-Profile Model for Design Consistency Evaluation." Transportation Research Record: Journal of the Transportation Research Board 1523, no. 1 (January 1996): 11–21. http://dx.doi.org/10.1177/0361198196152300102.
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The validity of a speed-profile model for design consistency evaluation was tested, including (a) the speed reduction estimation ability of the model and (b) assumptions about deceleration and acceleration characteristics approaching and departing horizontal curves. Detailed speed data were collected at a sample of 10 horizontal tangent-curve sections on two-lane rural highways in Texas. The results indicate that the model provides a reasonable, albeit simplified, representation of speed profiles on horizontal alignments consisting of long tangents and isolated curves. The model provides reasonable estimates of speed reductions from long approach tangents to curves but does not account for the effect of nearby intersections on speeds. The results also indicate that the assumed 0.85 m/sec2 value is reasonable for deceleration rates approaching curves that require speed reductions but may overestimate acceleration rates departing curves. The model's assumptions that deceleration occurs entirely on the approach tangent and that speeds are constant throughout a curve were not confirmed by observed speed behavior. The observations that deceleration continues after entering a curve and that speed adjustments occur throughout a curve are indicators of the difficulty drivers experience in judging appropriate speeds through curves.
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Xin, Chunfu, Zhenyu Wang, Chanyoung Lee, and Pei-Sung Lin. "Modeling Safety Effects of Horizontal Curve Design on Injury Severity of Single-Motorcycle Crashes with Mixed-Effects Logistic Model." Transportation Research Record: Journal of the Transportation Research Board 2637, no. 1 (January 2017): 38–46. http://dx.doi.org/10.3141/2637-05.
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Horizontal curves have been of great interest to transportation researchers because of expected safety hazards for motorcyclists. The impacts of horizontal curve design on motorcycle crash injuries are not well documented in previous studies. The current study aimed to investigate and to quantify the effects of horizontal curve design and associated factors on the injury severity of single-motorcycle crashes with consideration of the issue of unobserved heterogeneity. A mixed-effects logistic model was developed on the basis of 2,168 single-motorcycle crashes, which were collected on 8,597 horizontal curves in Florida for a period of 11 years (2005 to 2015). Four normally distributed random parameters (moderate curves, reverse curves, older riders, and male riders) were identified. The modeling results showed that sharp curves (radius <1,500 ft) compared with flat curves (radius ≥4,000 ft) tended to increase significantly the probability of severe injury (fatal or incapacitating injury) by 7.7%. In total, 63.8% of single-motorcycle crashes occurring on reverse curves are more likely to result in severe injury, and the remaining 26.2% are less likely to result in severe injury. Motorcyclist safety compensation behaviors (psychologically feeling safe, and then riding aggressively, or vice versa) may result in counterintuitive effects (e.g., vegetation and paved medians, full-access-controlled roads, and pavement conditions) or random parameters (e.g., moderate curve and reverse curve). Other significant factors include lighting conditions (darkness and darkness with lights), weekends, speed or speeding, collision type, alcohol or drug impairment, rider age, and helmet use.
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Kronprasert, Nopadon, Katesirint Boontan, and Patipat Kanha. "Crash Prediction Models for Horizontal Curve Segments on Two-Lane Rural Roads in Thailand." Sustainability 13, no. 16 (August 12, 2021): 9011. http://dx.doi.org/10.3390/su13169011.
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The number of road crashes continues to rise significantly in Thailand. Curve segments on two-lane rural roads are among the most hazardous locations which lead to road crashes and tremendous economic losses; therefore, a detailed examination of its risk is required. This study aims to develop crash prediction models using Safety Performance Functions (SPFs) as a tool to identify the relationship among road alignment, road geometric and traffic conditions, and crash frequency for two-lane rural horizontal curve segments. Relevant data associated with 86,599 curve segments on two-lane rural road networks in Thailand were collected including road alignment data from a GPS vehicle tracking technology, road attribute data from rural road asset databases, and historical crash data from crash reports. Safety Performance Functions (SPFs) for horizontal curve segments were developed, using Poisson regression, negative binomial regression, and calibrated Highway Safety Manual models. The results showed that the most significant parameter affecting crash frequency is lane width, followed by curve length, traffic volume, curve radius, and types of curves (i.e., circular curves, compound curves, reverse curves, and broken-back curves). Comparing among crash prediction models developed, the calibrated Highway Safety Manual SPF outperforms the others in prediction accuracy.
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Wang, Dan, Wei Gang Song, and Jie Liu. "Dynamic Design and Computer Imitation of Belt Conveyor with Horizontal Curves." Advanced Engineering Forum 2-3 (December 2011): 833–37. http://dx.doi.org/10.4028/www.scientific.net/aef.2-3.833.
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The dynamic design of a large belt conveyor with horizontal curves was studied in this paper. The method of calculating its running resistance was obtained by analyzing the orienting force and resistance on the curving parts of the belt conveyors. Dynamic equation of belt conveyor with horizontal curves by using discrete finite element model was established integrating the line-running parts and the curve-running parts. Additionally, dynamic analysis software of belt conveyor with horizontal curves was developed. Through simulation on real time system, start-up process and braking process were analyzed. The deviation of the belt was analyzed based on the tension, and the effect of curve running on belt conveyor was discussed.
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Sharf Aldeen, Asame, Ali Abdi Kordani, Seyed Mohsen Hosseinian, and Mehdi Mehdi Nazar. "Evaluation of the Application of Maximum Radius in Horizontal Curves Using Vehicle Dynamic Simulation." Advances in Civil Engineering 2022 (March 22, 2022): 1–19. http://dx.doi.org/10.1155/2022/5237541.
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Most road design standards recommend using a spiral curve for transitions. The main advantages of using this curve are the gradual increase in the centrifugal force, creating a suitable space for presenting superelevation, and providing a correct perception of the curve for the driver. In this research, vehicle dynamic simulation software CarSim and TruckSim is used to assess the forces imposed on the vehicles. In this regard, 360 scenarios are considered for sedans, SUVs, and trucks, which consist of variations of the road geometry (simple or spiral horizontal curve), curve radius, and type and speed of the vehicle. In addition, the regression analysis is performed to examine the relationships between the lateral acceleration (as a dependent variable) and the vehicle speed, curve radius, and vehicle type (as independent variables). The results indicate that in all cases, safety in the spiral horizontal curve is greater than that in the simple horizontal curve, and the maximum side friction factor, lateral acceleration, roll rate, roll angle, yaw rate, and lateral distance in the simple horizontal curve are higher than those in the spiral horizontal curve. Moreover, the difference percentage of the side friction factor, lateral acceleration, yaw rate, and lateral distance between the simple and spiral horizontal curves is the highest in SUVs, followed by sedans and trucks, while the difference percentage of the roll rate and roll angle is the highest in sedans, followed by SUVs and trucks. The results of regression analysis illustrate that the coefficient of determination (R2) in the proposed model is 0.972, 0.964, and 0.981 for sedans, SUVs, and trucks, respectively, indicating the strong relationships between the dependent and the explanatory variables as well as the capability of the model to cover the data.
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Hassan, Yasser, Said M. Easa, and A. O. Abd El Halim. "Modeling Headlight Sight Distance on Three-Dimensional Highway Alignments." Transportation Research Record: Journal of the Transportation Research Board 1579, no. 1 (January 1997): 79–88. http://dx.doi.org/10.3141/1579-10.
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Sight distance is one of the major elements that must be considered in the geometric design to achieve safe and comfortable highways. Daytime sight distance has been extensively studied, and analytical models for two-dimensional (2-D) and three-dimensional (3-D) alignments have been developed. However, nighttime (headlight) sight distance has received less attention. Despite the higher accident rate during nighttime than during daytime, existing analytical models evaluating headlight sight distance are very primitive. Moreover, the interaction between the horizontal and vertical alignments has not been modeled. A four-phase analytical model for headlight sight distance on 3-D combined alignments is presented. The model is an application of the finite-element technique in highway geometric design. The model can determine the maximum distance that can be covered by the vehicle’s headlights and that is not obstructed by any sight obstructions including the road surface. On the basis of this analytical model, computer software was developed and used in a preliminary application for 3-D headlight sight distances on a sag or crest vertical curve combined with a horizontal curve. The application showed that the 3-D sight distance on sag vertical curves was generally lower than the corresponding 2-D value when the sag curve was overlapping with a horizontal curve. On the other hand, the overlapping of horizontal curves with crest vertical curves enhanced the 3-D sight distance. The difference between 2-D and 3-D sight distance values in both cases increased with a decrease in the horizontal curve radius and an increase in the pavement cross slope. The model was proved to be extremely valuable in establishing 3-D highway geometric design standards.
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Hallmark, Shauna, Amrita Goswamy, Theresa Litteral, Neal Hawkins, Omar Smadi, and Skylar Knickerbocker. "Evaluation of Sequential Dynamic Chevron Warning Systems on Rural Two-Lane Curves." Transportation Research Record: Journal of the Transportation Research Board 2674, no. 10 (July 29, 2020): 648–57. http://dx.doi.org/10.1177/0361198120935872.
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Roadway departure crashes are a significant safety concern. The majority of these crashes occur on rural two-lane roadways, with a disproportionate number occurring on horizontal curves. The average crash rate for horizontal curves is about three times that of other highway segments. Curve-related crashes involve a number of roadway and driver causative factors, with speed being a preeminent factor. Implementing safety countermeasures on rural horizontal curves to address these crash types can improve the safety performance. Chevron alignment signs provide additional emphasis and guidance for drivers negotiating curves. To further emphasize the curve, some agencies have started using a sequential dynamic chevron warning system (SDCWS) which uses light emitting diode (LED) lights within each chevron sign to provide sequential lighted guidance through the curve. The research team evaluated 18 rural horizontal two-lane curves where a SDCWS had been implemented. Reference sites with similar characteristics were selected and included in the study. Models were developed using an empirical Bayes methodology for non-intersection (total) crashes and injury crashes. Additional countermeasures were present at some of the sites and were included in the model. Using these data, the study developed crash modification factors (CMFs) for SDCWS with a resulting CMF of 0.34 for total crashes (non-intersection) and 0.49 for injury crashes.
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Zheng, Xue Lian, Xian Sheng Li, Cheng Wu Jiao, Gang Bai, and Yuan Yuan Ren. "Study on Road Geometric Alignment Parameters Based on Vehicle Handling Stability Simulation." Applied Mechanics and Materials 404 (September 2013): 273–79. http://dx.doi.org/10.4028/www.scientific.net/amm.404.273.
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Unreasonable road geometric alignment has a negative influence on vehicle handling stability, especially when vehicle drives with a high speed. For horizontal road alignment, radius and banking of circular curve are the most popular and important parameters. To investigate the influence of horizontal road alignment on vehicle handling stability, a 3 degrees-of-freedom vehicle dynamic model is established. Three road horizontal curves with different radius are established in Carsim environment to investigate the influence of curve radius on vehicle handling stability and four different banking curve roads are built to study the impact of road banking on vehicle roll stability. The research achievement will provide theoretical basis and technical support for road geometric alignment design.
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Bonneson, James A. "Kinematic Approach to Horizontal Curve Transition Design." Transportation Research Record: Journal of the Transportation Research Board 1737, no. 1 (January 2000): 1–8. http://dx.doi.org/10.3141/1737-01.
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Research has shown that vehicles shift laterally in the traffic lane during their entry to (or exit from) a horizontal curve. In addition, research indicates that most drivers momentarily adopt a path radius that is sharper than that of the roadway curve. A study was undertaken to investigate the causes of lateral shift and sharp path radii and to determine if they can be minimized (or eliminated) by modifying the horizontal curve transition design. From a review of the driver–vehicle control process, it was concluded that lane shift is due to unbalanced lateral accelerations that act on the vehicle as it enters the curve. These accelerations result from gravity, as effected through roadway superelevation, and side friction, caused by the steer angle of the vehicle. Kinematic models of lateral acceleration, velocity, and shift were developed. The calibrated models were used to develop design guidelines for superelevation rate and superelevation runoff location.
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Grunberg, J. "The horizontal curve of the dental arch." European Journal of Orthodontics 32, no. 6 (November 24, 2010): e158-e160. http://dx.doi.org/10.1093/ejo/cjq136.
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Musey, K., and S. Park. "Pavement Skid Number and Horizontal Curve Safety." Procedia Engineering 145 (2016): 828–35. http://dx.doi.org/10.1016/j.proeng.2016.04.108.
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Cvitanić, Dražen, and Biljana Maljković. "Determination of Applicable Adjacent Horizontal Curve Radii Using Operating Speed." PROMET - Traffic&Transportation 31, no. 4 (August 23, 2019): 443–52. http://dx.doi.org/10.7307/ptt.v31i4.3088.
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Design of curves and their adjacent elements presents the greatest safety problem on rural two-lane roads. The use of the existing alignment consistency safety criteria (design, operating speed, and driving dynamic consistency) could have some shortcomings, especially in countries where the project or design speed is in use instead of (higher) operating speed. The consequence is that the designer should use smaller cross fall on curves than needed, while the calculated side friction is lower than in reality. Further, the existing graphs of adjacent curve radii do not take into account that there is a maximum operating speed achieved for a certain radius or long tangent above which it does not increase. This paper presents a methodology for determination of adjacent horizontal curve radii, with and without tangent between, based on the operating speed models which include dependence of operating speeds on tangents and curves on speed of adjacent alignment elements as well as maximum tangent and curve speed. The developed graphs of adjacent radii at the same time include the limiting values of driving dynamic consistency criteria, so the road designer does not need to calculate permissible and demand side friction for every combination of adjacent alignment elements.
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Wood, Jonathan S., and Shaohu Zhang. "Identification and Calculation of Horizontal Curves for Low-Volume Roadways Using Smartphone Sensors." Transportation Research Record: Journal of the Transportation Research Board 2672, no. 39 (April 27, 2018): 1–10. http://dx.doi.org/10.1177/0361198118759005.
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Horizontal curves are a contributing factor to the number of observed roadway crashes. Identifying locations and geometric characteristics of horizontal curves plays a crucial role in crash prediction and prevention. However, most states in the USA face a challenge in maintaining detailed and high-quality roadway inventory databases for low-volume rural roads due to the labor-intensive and time-consuming nature of collecting and maintaining the data. This paper proposes a low-cost mobile road inventory system for two-lane horizontal curves based on off-the-shelf smartphones. The proposed system is capable of accurately detecting horizontal curves by exploiting a K-means machine learning technique. Butterworth low-pass filtering is applied to reduce sensor noise. Extended Kalman filtering is adopted to improve the GPS accuracy. Chord method-based radius computation and superelevation estimation are introduced to achieve accurate and robust results despite the low-frequency GPS and noisy sensor signals obtained from smartphones. This study implements this method using an Android-based smartphone and tests 21 horizontal curves in South Dakota. The results demonstrate that the proposed system achieves high curve identification accuracy as well as high accuracy for calculating curve radius and superelevation.
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Wooldridge, Mark D., Kay Fitzpatrick, Rodger Koppa, and Karin Bauer. "Effects of Horizontal Curvature on Driver Visual Demand." Transportation Research Record: Journal of the Transportation Research Board 1737, no. 1 (January 2000): 71–77. http://dx.doi.org/10.3141/1737-09.
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A consistent design allows drivers to perform safely the task of driving, allowing attention or capacity to be dedicated to obstacle avoidance and navigation. A measure of the consistency of a design is the amount of visual information needed by a driver to maintain an acceptable path on the roadway. Vision occlusion is a technique that measures driver visual demand on a roadway. It allows a more direct evaluation of the effects of various geometric elements on the driver. Studies of the effects of variations of curve radius, deflection angle, spacing, and sequences revealed several relationships between roadway geometry and visual demand. Curve radius and its reciprocal were found to be significantly related to visual demand in both on-road and test track studies. Small changes in visual demand were also found between types of curve pairs (S and broken back) with differing spacing between the curves. Visual demand was found to be a promising measure of effectiveness for use in studies of design consistency.
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Cook, Aaron A., Mitsuru Saito, and Grant G. Schultz. "Heuristic Approach to Identifying Horizontal Curves and Their Parameters Given Lidar Point Cloud Data." Transportation Research Record: Journal of the Transportation Research Board 2521, no. 1 (January 2015): 22–30. http://dx.doi.org/10.3141/2521-03.
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Information on the location and characteristics of highways has many applications to highway engineering, such as highway safety analysis, asset management, and highway improvement planning. However, the task of creating an inventory of highway curves in a state is a daunting task, which cannot be done efficiently by field visits. The alternative approach that processes light detection and ranging or GPS data sets to identify highway curves has shown promise as a more efficient method but has also proved to be a difficult task. This paper presents a procedure for curve detection and analysis and also examines the success rate for identification and classification of those curves identified by this method. The basic process began with the roadway divided into segments, each with assigned attributes. The segments with similar attributes were combined into larger sections, each classified as either a curve or a tangent. Segments that were too short to be a true curve were removed. The heuristic analysis used to optimize threshold values for the analysis of these curves was also discussed. It was found that the curve identification success rate of this process, depending on calibration, ranged from 84.4% to 92.9% accuracy (e.g., the segment identified correctly as a curve or tangent), and curve geometries (e.g., points of curvature or points of tangency location correctly found) could be expected to have an accuracy rate of 78.7% to 89.9%.
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Rose, Elisabeth R., and Paul J. Carlson. "Spacing Chevrons on Horizontal Curves." Transportation Research Record: Journal of the Transportation Research Board 1918, no. 1 (January 2005): 84–91. http://dx.doi.org/10.1177/0361198105191800111.
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The chevron alignment sign is an important traffic control device used to warn drivers of the severity of a curve by delineating the alignment of the road around that curve. FHWA's Manual on Uniform Traffic Control Devices for Streets and Highways provides the following guidance on the spacing of chevrons around a curve: “The Chevron Alignment sign should be spaced such that the road user always has at least two in view, until the change in alignment eliminates the need for the signs” and “the Chevrons should be visible for a sufficient distance to provide the road user with adequate time to react to the change in alignment.” This guidance is broad to account for geometric design features and site obstructions such as steep vertical curvature or heavy vegetation. It also allows flexibility based on site characteristics and available funds, and the use of this verbiage creates a lower liability risk than there would be if a spacing chart were used. However, the broad wording allows for inconsistencies in the roadway system and provides little guidance for maintenance personnel. A field study was conducted to investigate the impacts of varying the number of chevrons in view around a curve. A spacing chart was then developed to simplify maintenance personnel's responsibility for choosing appropriate chevron spacing. The results of the field study indicated that having more than two chevrons in view around the curve provided a benefit in the form of a reduction in speed of about 3 mph at night. Smaller speed reductions were observed during daylight.
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Echaveguren, Tomás, Marcelo Bustos, and Hernán de Solminihac. "Assessment of horizontal curves of an existing road using reliability concepts." Canadian Journal of Civil Engineering 32, no. 6 (December 1, 2005): 1030–38. http://dx.doi.org/10.1139/l05-056.
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Horizontal curves on road are commonly analyzed under design speed point of view, where it is assumed that the maximum speed of a vehicle in a curve is the design speed. The empirical evidence has demonstrated that when the design speed is low, the operating speed tends to be higher. This happens because of an available remaining lateral (or transverse) friction for speeds over design speed. This condition is determined by a speed limit, obtained from the demand and supply equilibrium of friction of a pavement. The difference between operating and design speeds is usually considered as the margin of safety of a horizontal curve on a road. In this study, a methodology to determine the margin of safety of an existing curve is proposed. The methodology is based on the reliability theory by which reliability of operational conditions can be analyzed by using a reliability index as a margin of safety. A case study for light vehicles is evaluated to determine high impact variables over reliability, such as, macrotexture, skid resistance, curve radius, and superelevation. The results obtained in this study demonstrated that curve radius, skid resistance, and macrotexture are variables with high impact over failure probability. In constrast, superelevation has little effect on the failure probability.Key words: reliability, horizontal curves, operating speed, skid resistance, pavement texture.
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Gargoum, Suliman, Karim El-Basyouny, and Joseph Sabbagh. "Automated Extraction of Horizontal Curve Attributes using LiDAR Data." Transportation Research Record: Journal of the Transportation Research Board 2672, no. 39 (May 7, 2018): 98–106. http://dx.doi.org/10.1177/0361198118758685.
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Horizontal curves are designed to provide a safe and smooth transition between straight segments on a highway network. Although curves are often designed to meet very stringent standards, imperfections during construction and high operating speeds mean that they are still prone to collisions. Therefore, it is essential that attributes of curves are surveyed to ensure they meet design requirements. Moreover, knowledge of the locations of horizontal curves and their attributes is also required to provide drivers with accurate information in advanced curve-warning systems, which are expected to enhance safety. Unfortunately, conventional techniques to obtain information about horizontal alignments are extremely tedious and, in some cases, impractical. This paper proposes a method by which horizontal curves can be automatically detected and their attributes automatically measured on scans of the highways obtained using light detection and ranging (LiDAR) technology. The proposed method is tested on two different highway segments at the Province of Alberta, Canada, where LiDAR data were collected. Moreover, testing was also conducted using virtual highways with curves with known attributes generated in AutoCAD Civil 3D. The results show that the code is successful in detecting all curves on a highway segment; moreover, the attributes of those curves were estimated with a high degree of accuracy (average difference <3%).
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Faiz, Rizwan Ullah, Nordiana Mashros, and Sitti Asmah Hassan. "Speed Behavior of Heterogeneous Traffic on Two-Lane Rural Roads in Malaysia." Sustainability 14, no. 23 (December 2, 2022): 16144. http://dx.doi.org/10.3390/su142316144.
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Highway geometry is a significant factor that affects the efficiency and safety of highway systems. The present study aims to investigate the speed behavior of various vehicle classes on the horizontal alignment of two-lane rural roads. An automatic data collection system based on a pressure sensor was employed to collect the speed of each individual vehicle, vehicle type, and headway at seven sites in each travel direction. The 85th percentile speed under free-flow conditions was used to observe the relationship between the operating speeds of various vehicle classes at consecutive curve points and the effect of the travel direction, time of day, and curve radius on the operating speed of the vehicle. A one-way ANOVA was employed to evaluate whether there is a significant difference in speed on horizontal curves. Then, a Tukey post hoc test was used to assess the significance of the difference in speed across four classes of vehicles. The results revealed that the horizontal curve affects the operating speed for all vehicle classes. A curve radius of less than 500 m, the travel direction, and the time of day are significant variables that affect the speed of all vehicle classes. The findings from this study can provide insight to transportation engineers for safer road design of horizontal curves and to assess traffic safety based on actual speed behavior.
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Wang, Song, and Zhixia Li. "Roadside Sensing Information Enabled Horizontal Curve Crash Avoidance System Based on Connected and Autonomous Vehicle Technology." Transportation Research Record: Journal of the Transportation Research Board 2673, no. 5 (March 22, 2019): 49–60. http://dx.doi.org/10.1177/0361198119837957.
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Horizontal curves are a major cause of road departure crashes that lead to fatal and severe injuries. Existing curve crash avoidance systems are typically enabled by displaying safety messages via in-vehicle heads-up/down display. However, these systems just pass the information to drivers. The final decision to reduce or maintain speed in response to the safety message is still the human driver’s. Because of the involvement of the human factor, there is potential for road departure crashes to happen if human drivers do not respond to safety messages appropriately. Autonomous vehicle (AV) technology targets elimination of human error in driving through an automated driving system. In this context, this paper proposes a conceptual prototype of a connected and AV-based horizontal curve crash avoidance system (CAV-HCCAS), aiming at achieving a permanent solution to horizontal curve safety by excluding human error through automated driving. In CAV-HCCAS, a roadside sensor detects pavement wetness level at the horizontal curve and communicates it to the vehicle via dedicated short-range communication. By processing the pavement wetness information, the AV applies a safe curve travel speed that reflects the real-time pavement conditions. An automated driving simulation experiment was performed to prove the concept. Dry and wet pavement conditions were simulated for a horizontal curve. Lane deviation data and the resulting lane departure conflicts were measured as safety performance measures. Results indicate a significant reduction of lane departure conflicts when CAV-HCCAS is implemented under both dry and wet pavement conditions, which reflects a substantial safety benefit.
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Turhan, Essin, and Talat Körpinar. "On Characterization Canal Surfaces around Timelike Horizontal Biharmonic Curves in Lorentzian Heisenberg Group Heis3." Zeitschrift für Naturforschung A 66, no. 6-7 (July 1, 2011): 441–49. http://dx.doi.org/10.1515/zna-2011-6-709.
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In this paper, we describe a new method for constructing a canal surface surrounding a timelike horizontal biharmonic curve in the Lorentzian Heisenberg group Heis3. Firstly, we characterize timelike biharmonic curves in terms of their curvature and torsion. Also, by using timelike horizontal biharmonic curves, we give explicit parametrizations of canal surfaces in the Lorentzian Heisenberg group Heis3
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Jeong, Heejin, and Yili Liu. "Horizontal Curve Driving Performance and Safety Affected by Road Geometry and Lead Vehicle." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 61, no. 1 (September 2017): 1629–33. http://dx.doi.org/10.1177/1541931213601893.
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To help enhance safety and reduce crashes occurred on horizontal curved roads, it is important to understand their potential causes. The study reported in this paper aimed to examine the effects of road geometry (i.e., road curvature and curve direction) and lead vehicle on horizontal curve driving performance. Twenty-four participants performed two driving tasks (i.e., car-following and free- flow conditions) in simulated driving scenarios including curved roads in both right and left directions to measure their driving performance (e.g., speed, lane position, steering wheel angle, and time and distance headways). The results showed that road curvature affected driving performance, especially in mean speed, variability of lane-keeping performance, and headway. Moreover, the mean speed was affected by both road curvature and whether a lead vehicle existed. Findings from this study provide empirical data that can be used for driving safety on horizontal curved roads.
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Easa, Said, and Essam Dabbour. "Establishing design guidelines for compound horizontal curves on three-dimensional alignments." Canadian Journal of Civil Engineering 32, no. 4 (August 1, 2005): 615–26. http://dx.doi.org/10.1139/l05-016.
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In current design guides, the minimum radii of compound horizontal curves are based on the design requirements of simple horizontal curves for each arc on flat terrain. Such a design ignores the effects of compound curvature and vertical alignment. This paper uses computer simulation software to establish the minimum radius requirements for compound curves, considering these effects. The actual lateral acceleration experienced by a vehicle negotiating a two-dimensional (2-D) simple curve is recorded as a base scenario to facilitate the analysis of a compound curve on a flat terrain or combined with vertical alignment (three-dimensional (3-D) compound curves). The vertical alignments examined include upgrades, downgrades, crest curves, and sag curves. Mathematical models for minimum radius requirements were developed for flat and 3-D compound curves. Three types of design vehicles were used. The results show that an increase in the minimum radius ranging from 5% to 26% is required to compensate for the effects of both compound curvature and vertical alignment.Key words: highway geometric design, compound horizontal alignments, side friction, vehicle simulation, 3-D alignments.
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Liu, Jiang. "Highway Alignment Parameters Design and Capacity Analysis on Two-Lane Highway." Applied Mechanics and Materials 539 (July 2014): 860–66. http://dx.doi.org/10.4028/www.scientific.net/amm.539.860.
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A two-lane highway is an undivided highway with only one lane of traffic in each direction. Two-lane highways are one of the most common roadways at mountainous areas in China. Due to the wider range to choose the horizontal and vertical curves in the design of two-lane highways, the combination of both leads to larger differences on two-lane highway capacities. Thus, the highway alignments are one of the key factors which affect the two-lane highway capacities. According to the empirical data and existing studies, it is regarded that there is no impacts on the capacity for horizontal curves with a radius more than 400m and vertical curves with the gradient less than 3%. Two concepts are defined as effective bending and effective gradient which represent the extent the horizontal curve bends and the steepness of vertical curve respectively. The method to calculate effective bending of horizontal curve and steepness of vertical curve is given and its relevant properties are also discussed. According to the simulation results and the principle of speed differences, the effective bending and effective gradient have been classified into 7 and 6 levels, separately. As a result, there will be 42 combinations of different highway alignments of two-lane highways based on the different combinations of the effective bending and effective gradient. Under this circumstance, the relationship of speed-volume and volume-PTSF (percent time spend following) are obtained from the simulation results. Finally, the capacity of two-lane highway is given under different highway alignments of two-lane highway at mountainous areas in China.
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Rohani, Munzilah Md, Rosnawati Buhari, Basil David Daniel, Joewono Prestijo, Kamaruddin Ambak, Norsabahiah Abd Sukor, and Sitti Asmah Hasan. "Car Driving Behaviour on Road Curves: A Study Case in Universiti Tun Hussein Onn Malaysia." Applied Mechanics and Materials 773-774 (July 2015): 990–95. http://dx.doi.org/10.4028/www.scientific.net/amm.773-774.990.
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The World Health Organization (WHO) predicted that in 2020, road accidents will become the third cause of deaths in the world. Several factors contribute to road accidents, among them are human error, speeding, irregularities in road design and period of driving (either nighttime or daytime). In road design, horizontal curves are of particular interest to the designer, given that accidents are very likely to occur at such locations if drivers lose control of their vehicles due to inappropriate speed choices. This study was conducted to investigate the variation of driving behaviour on horizontal curves. The test car was fitted with a Global Positioning System (GPS) device and driven by 30 participants. The research findings show that drivers’ choice of speed varies while approaching horizontal curve, on the curve and just after leaving the curve. Apart from this, although drivers were found to have driven at a slightly higher speed during daytime compare to evening driving, however the difference was not significant. A comparison between genders also revealed that female and male drivers drive at similar speed behaviour
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Huang, Zhi Lu, and Kuan Min Chen. "Research on the Quantitative Technical Index of Combining Horizontal and Vertical Curves of Expressway." Applied Mechanics and Materials 668-669 (October 2014): 1442–48. http://dx.doi.org/10.4028/www.scientific.net/amm.668-669.1442.
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The factors of combining horizontal and vertical curves are analyzed for guiding road design on expressway in practice and ensuring the safety and comfort of vehicle. The influences on drivers' by all kinds of flat vertical combination characteristics are researched. The necessary conditions meeting the horizontal and vertical combination rationality are proposed through the highway and driver characteristics. The identification sight on convex and concave vertical curve under driving at night and overpass are studied based on driver's sight guidance; the indexes of the vertical curve radius and length that my not meet horizontal including vertical combination are raised. Based on road surface drainage, the indexes that may not meet horizontal including vertical combination is proposed from the aspects of longitudinal slope, cross slope drainage and pavement structure. Comprehensive the design of flat vertical combination put forward the quantitative technical indicators that may not meet horizontal including vertical combination.
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Buddhavarapu, Prasad, Ambarish Banerjee, and Jorge A. Prozzi. "Influence of pavement condition on horizontal curve safety." Accident Analysis & Prevention 52 (March 2013): 9–18. http://dx.doi.org/10.1016/j.aap.2012.12.010.
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Hassan, Yasser, and Said M. Easa. "Sight distance red zones on combined horizontal and sag vertical curves." Canadian Journal of Civil Engineering 25, no. 4 (August 1, 1998): 621–30. http://dx.doi.org/10.1139/l97-127.
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Coordination of highway horizontal and vertical alignments is based on subjective guidelines in current standards. This paper presents a quantitative analysis of coordinating horizontal and sag vertical curves that are designed using two-dimensional standards. The locations where a horizontal curve should not be positioned relative to a sag vertical curve (called red zones) are identified. In the red zone, the available sight distance (computed using three-dimensional models) is less than the required sight distance. Two types of red zones, based on stopping sight distance (SSD) and preview sight distance (PVSD), are examined. The SSD red zone corresponds to the locations where an overlap between a horizontal curve and a sag vertical curve should be avoided because the three-dimensional sight distance will be less than the required SSD. The PVSD red zone corresponds to the locations where a horizontal curve should not start because drivers will not be able to perceive it and safely react to it. The SSD red zones exist for practical highway alignment parameters, and therefore designers should check the alignments for potential SSD red zones. The range of SSD red zones was found to depend on the different alignment parameters, especially the superelevation rate. On the other hand, the results showed that the PVSD red zones exist only for large values of the required PVSD, and therefore this type of red zones is not critical. This paper should be of particular interest to the highway designers and professionals concerned with highway safety.Key words: sight distance, red zone, combined alignment.