Influence of vertical alignment on horizontal curve perception: effect of spirals and position of vertical curve

2005 ◽  
Vol 32 (1) ◽  
pp. 204-212 ◽  
Author(s):  
Moudud Hasan ◽  
Tarek Sayed ◽  
Yasser Hassan
Keyword(s):  
Visual Perception ◽  
Statistical Models ◽  
Geometric Design ◽  
Geometric Parameters ◽  
Horizontal Curve ◽  
Vertical Alignment ◽  
Two Phase ◽  
Horizontal Curves ◽  
Phase Study ◽  
Horizontal Curvature

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.

Effect of driver and road characteristics on required preview sight distance

2002 ◽  
Vol 29 (2) ◽  
pp. 276-288 ◽  
Author(s):  
Yasser Hassan ◽  
Tarek Sayed
Keyword(s):  
Computer Animation ◽  
Linear Regression Analysis ◽  
Three Dimensional ◽  
Human Perception ◽  
Physical Modelling ◽  
Geometric Design ◽  
Geometric Parameters ◽  
Horizontal Curve ◽  
Sight Distance ◽  
Road Characteristics

Highway geometric design is a complex process that is closely related to human perception and behaviour. Among the human perception issues that can affect highway geometric design is the preview sight distance, which has been defined as the distance required to perceive a horizontal curve and react properly to it. Previous attempts to quantify preview sight distance included measurement on actual roads, physical modelling, and computer animation. This paper presents a computer animation experiment that was designed to examine the effects of geometric parameters and driver characteristics on preview sight distance and to statistically model preview sight distance. Statistical analysis showed that preview sight distance depends on geometric parameters such as the horizontal curve radius, use of spiral curve and its length, presence of crest vertical curve, algebraic difference of vertical grades, vertical curvature, and road delineation. On the other hand, driver characteristics were mostly found to be insignificant parameters. Finally, statistical models were developed to predict the value of preview sight distance using linear regression analysis. The models vary in simplicity and accuracy and were formulated as a function of the general alignment configuration or as a function of the exact geometric parameters.Key words: highway geometric design, sight distance, driver characteristics, three-dimensional alignment.

scholarly journals OPERATING SPEED PREDICTION MODEL AS A TOOL FOR CONSISTENCY BASED GEOMETRIC DESIGN OF FOUR-LANE DIVIDED HIGHWAYS

Transport ◽  
2019 ◽  
Vol 34 (4) ◽  
pp. 425-436 ◽  
Author(s):  
Gourab Sil ◽  
Avijit Maji ◽  
Suresh Nama ◽  
Akhilesh Kumar Maurya
Keyword(s):  
Prediction Model ◽  
Lateral Position ◽  
Geometric Design ◽  
Operating Speed ◽  
Vehicle Speed ◽  
Horizontal Curve ◽  
Passenger Cars ◽  
Horizontal Curves ◽  
Speed Prediction ◽  
Design Consistency

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.

scholarly journals Modelling of Three-Dimensional Intersection Sight Distance

2021 ◽  
Author(s):  
Muhammad Zain Abrahim Ali
Keyword(s):  
Three Dimensional ◽  
Design Element ◽  
Major Road ◽  
Horizontal Curve ◽  
Vertical Alignment ◽  
Left Turn ◽  
Horizontal Curves ◽  
Sight Distance ◽  
Minor Road ◽  
Left Turns

Intersection sight distance(ISD) is an important design element. Each intersection has a potential for several different types of vehicular conflicts that can be greatly reduced through the provision of proper sight distance. Current guidelines do not adequately address sight distance requirements for intersections located on horizontal curves alone or horizontal curves combined with vertical alignments. In many practical situations, however, sight distance is required to be checked for an existing or proposed three-dimensional(3D) intersection alignments. In this thesis, models were developed to check sight (2001) were considered on 3D alignment: (1)Departure from stop-control minor-road and (2) Left-turns from major-road. For stop-control intersections, several cases were addressed. These include Case 1(a): Intersection and approaching vehicle (object) lie on the curve, Case 2: Intersection lies on the tangent and object lies on the curve. For both cases (1) and (2), obstruction may lie inside or outside the horizontal curve and the intersection and object can be anywhere with respect to the vertical alignment. In many practical situations, however, sight distance is required to be checked for an existing or proposed three-dimensional(3D) intersection alignments. In this thesis, models were developed to check sight (2001) were considered on 3D alignment: (1)Departure from stop-control minor-road and (2) Left-turns from major-road. For stop-control intersections, several cases were addressed. These include Case 1(a): Intersection and approaching vehicle (object) lie on the curve, Case 2: Intersection lies on the tangent and object lies on the curve. For both cases (1) and (2), obstruction may lie inside or outside the horizontal curve and the intersection and object can be anywhere with respect to the vertical alignment. Design aids for required minimum lateral clearance (from the minor and major roads) are presented for different radii of intersections located on horizontal curves, guidelines are presented for offsetting opposing left-turn lanes to provide unobstructed required sight distance. Applications of the methodologies are illustrated using numerical examples.

Simplifying Delineator Applications for Horizontal Curves

2005 ◽  
Vol 1918 (1) ◽  
pp. 68-75 ◽  
Author(s):  
Susan T. Chrysler ◽  
Paul J. Carlson ◽  
Alicia A. Williams
Keyword(s):  
Human Factors ◽  
Traffic Control ◽  
Horizontal Curve ◽  
Horizontal Curves ◽  
Spacing Pattern ◽  
Variable Approach ◽  
Control Devices ◽  
The Difference ◽  
Horizontal Curvature ◽  
Single Versus

The human factors study being reported measured drivers’ estimates of horizontal curvature as a function of the size and spacing characteristics of post-mounted delineators. The study also assessed drivers’ understanding of delineator color applications. The main objective of this study was to provide support for simplifying delineator applications of FHWA's Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD), particularly the need to distinguish between single and double delineators and the need to have variable approach and departure horizontal curve delineator spacing. A closed-course nighttime study was conducted with 24 drivers aged 22 to 72 in a passenger sedan with low-beam headlights. Drivers rated their estimates of curvature for large- and small-radii curves from three stationary viewing distances. In addition, participants completed a test of their memory for the proper placement of yellow and white reflectors using photographs of roadways. Results from the visibility study show that drivers cannot distinguish between single and double delineators and they cannot distinguish between variable spacing and fixed spacing on approaches to horizontal curves. The results from the photograph test show that drivers do not understand the difference in placement for yellow and white delineators. As a result, the recommendations include the elimination of the single versus double delineator distinction in MUTCD and the use of a fixed spacing pattern for delineators on the approach to and departure from horizontal curves.

scholarly journals Modelling of Three-Dimensional Intersection Sight Distance

2021 ◽  
Author(s):  
Muhammad Zain Abrahim Ali
Keyword(s):  
Three Dimensional ◽  
Design Element ◽  
Major Road ◽  
Horizontal Curve ◽  
Vertical Alignment ◽  
Left Turn ◽  
Horizontal Curves ◽  
Sight Distance ◽  
Minor Road ◽  
Left Turns

Intersection sight distance(ISD) is an important design element. Each intersection has a potential for several different types of vehicular conflicts that can be greatly reduced through the provision of proper sight distance. Current guidelines do not adequately address sight distance requirements for intersections located on horizontal curves alone or horizontal curves combined with vertical alignments. In many practical situations, however, sight distance is required to be checked for an existing or proposed three-dimensional(3D) intersection alignments. In this thesis, models were developed to check sight (2001) were considered on 3D alignment: (1)Departure from stop-control minor-road and (2) Left-turns from major-road. For stop-control intersections, several cases were addressed. These include Case 1(a): Intersection and approaching vehicle (object) lie on the curve, Case 2: Intersection lies on the tangent and object lies on the curve. For both cases (1) and (2), obstruction may lie inside or outside the horizontal curve and the intersection and object can be anywhere with respect to the vertical alignment. In many practical situations, however, sight distance is required to be checked for an existing or proposed three-dimensional(3D) intersection alignments. In this thesis, models were developed to check sight (2001) were considered on 3D alignment: (1)Departure from stop-control minor-road and (2) Left-turns from major-road. For stop-control intersections, several cases were addressed. These include Case 1(a): Intersection and approaching vehicle (object) lie on the curve, Case 2: Intersection lies on the tangent and object lies on the curve. For both cases (1) and (2), obstruction may lie inside or outside the horizontal curve and the intersection and object can be anywhere with respect to the vertical alignment. Design aids for required minimum lateral clearance (from the minor and major roads) are presented for different radii of intersections located on horizontal curves, guidelines are presented for offsetting opposing left-turn lanes to provide unobstructed required sight distance. Applications of the methodologies are illustrated using numerical examples.

scholarly journals Three-Dimensional Analysis of the In Vivo Motion of Implantable Cardioverter Defibrillator Leads

2021 ◽  
Author(s):  
Tamas Szili-Torok ◽  
Jens Rump ◽  
Torsten Luther ◽  
Sing-Chien Yap
Keyword(s):  
Three Dimensional ◽  
Second Phase ◽  
Two Phase ◽  
Maximum Curvature ◽  
Phase Study ◽  
Absolute Curvature ◽  
Icd Leads ◽  
Lead Testing ◽  
Design And Testing

Abstract Better understanding of the lead curvature, movement and their spatial distribution may be beneficial in developing lead testing methods, guiding implantations and improving life expectancy of implanted leads. Objective The aim of this two-phase study was to develop and test a novel biplane cine-fluoroscopy-based method to evaluate input parameters for bending stress in leads based on their in vivo 3D motion using precisely determined spatial distributions of lead curvatures. Potential tensile, compressive or torque forces were not subjects of this study. Methods A method to measure lead curvature and curvature evolution was initially tested in a phantom study. In the second phase using this model 51 patients with implanted ICD leads were included. A biplane cine-fluoroscopy recording of the intracardiac region of the lead was performed. The lead centerline and its motion were reconstructed in 3D and used to define lead curvature and curvature changes. The maximum absolute curvature Cmax during a cardiac cycle, the maximum curvature amplitude Camp and the maximum curvature Cmax@amp at the location of Camp were calculated. These parameters can be used to characterize fatigue stress in a lead under cyclical bending. Results The medians of Camp and Cmax@amp were 0.18 cm−1 and 0.42 cm−1, respectively. The median location of Cmax was in the atrium whereas the median location of Camp occurred close to where the transit through the tricuspid valve can be assumed. Increased curvatures were found for higher slack grades. Conclusion Our results suggest that reconstruction of 3D ICD lead motion is feasible using biplane cine-fluoroscopy. Lead curvatures can be computed with high accuracy and the results can be implemented to improve lead design and testing.

Modeling Safety Effects of Horizontal Curve Design on Injury Severity of Single-Motorcycle Crashes with Mixed-Effects Logistic Model

2017 ◽  
Vol 2637 (1) ◽  
pp. 38-46 ◽  
Author(s):  
Chunfu Xin ◽  
Zhenyu Wang ◽  
Chanyoung Lee ◽  
Pei-Sung Lin
Keyword(s):  
Logistic Model ◽  
Injury Severity ◽  
Unobserved Heterogeneity ◽  
Mixed Effects ◽  
Severe Injury ◽  
Horizontal Curve ◽  
Random Parameters ◽  
Horizontal Curves ◽  
Curve Design ◽  
Motorcycle Crashes

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.

Multicenter Transversal Two-Phase Study to Determine a National Prevalence of Epilepsy in Algeria

2012 ◽  
Vol 39 (2) ◽  
pp. 131-134 ◽  
Author(s):  
Dalila Moualek ◽  
Lamia Ali Pacha ◽  
Samira Abrouk ◽  
Mohamed Islam Kediha ◽  
Sonia Nouioua ◽  
...  
Keyword(s):  
Two Phase ◽  
Phase Study ◽  
National Prevalence

Endometrial Adenocarcinoma in SurePath™ Cervical Samples: Cytological Features Revisited

2016 ◽  
Vol 60 (1) ◽  
pp. 46-52 ◽  
Author(s):  
Nalini Gupta ◽  
John Crossley ◽  
Nick Dudding ◽  
John H.F. Smith
Keyword(s):  
Phase 1 ◽  
Endometrial Adenocarcinoma ◽  
Nuclear Chromatin ◽  
Phase 2 ◽  
Cervical Lesions ◽  
Two Phase ◽  
Endometrial Cells ◽  
Phase Study ◽  
Cytological Features ◽  
Liquid Based Cytology

Objective: The cytomorphological criteria of malignant endometrial lesions in cervical samples are less well described than those of cervical lesions. We wished to investigate if there were features in SurePath™ liquid-based cytology samples that would facilitate more accurate differentiation between benign and malignant endometrial cells. Study Design: This was a two-phase study, with a review of all SurePath™ samples reported as endometrial adenocarcinoma (n = 42) evaluating 12 cytological features in the first phase. In phase 2 (test set), all initial cases plus an additional 83 cases were reviewed using these 12 cytological features to predict the outcome. Results: Out of 12 cytological features evaluated in phase 1 (training set), nuclear chromatin pattern, apoptotic bodies and tingible body macrophages were found to be the most significant features determining malignant histological outcome. These 12 cytological features were re-evaluated in phase 2 (n = 125). Of 125 cases, 54 had a benign and 71 had a malignant or premalignant histological outcome, with a positive predictive value of 56.8%. Conclusion: Granular nuclear chromatin, tingible body macrophages and apoptosis in the background are the most significant factors in determining whether endometrial cells present in cervical samples represent malignancy or are benign. Using these features, relatively accurate predictions of endometrial pathology can be made.

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