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.

Modeling Headlight Sight Distance on Three-Dimensional Highway Alignments

1997 ◽  
Vol 1579 (1) ◽  
pp. 79-88 ◽  
Author(s):  
Yasser Hassan ◽  
Said M. Easa ◽  
A. O. Abd El Halim
Keyword(s):  
Analytical Model ◽  
Three Dimensional ◽  
Computer Software ◽  
Major Elements ◽  
Geometric Design ◽  
Analytical Models ◽  
Horizontal Curve ◽  
Design Standards ◽  
Sight Distance ◽  
Element Technique

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.

Sight distance red zones on combined horizontal and sag vertical curves

1998 ◽  
Vol 25 (4) ◽  
pp. 621-630 ◽  
Author(s):  
Yasser Hassan ◽  
Said M Easa
Keyword(s):  
Quantitative Analysis ◽  
Three Dimensional ◽  
The Other ◽  
Two Dimensional ◽  
Horizontal Curve ◽  
Sight Distance ◽  
Stopping Sight Distance ◽  
Three Dimensional Models ◽  
Highway Alignment ◽  
Current Standards

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.

State-of-the-art of three-dimensional highway geometric design

1998 ◽  
Vol 25 (3) ◽  
pp. 500-511 ◽  
Author(s):  
Yasser Hassan ◽  
Said M Easa ◽  
A O Abd El Halim
Keyword(s):  
Traffic Safety ◽  
Vehicle Dynamics ◽  
Research Work ◽  
Three Dimensional ◽  
Computer Software ◽  
Design Criterion ◽  
Geometric Design ◽  
Analytical Models ◽  
Sight Distance ◽  
Current Standards

Geometric design is an important phase in the highway design process that is directly related to traffic safety. Highway elements should be jointly designed to account for such design criteria as sight distance, vehicle stability, driver comfort, drainage, and aesthetics. Intuitively, such a design should be based on a three-dimensional (3-D) analysis. This paper reviews the current practice and research work related to each design criterion with emphasis on the conformity with the 3-D nature of the highway. Current standards are based mainly on a two-dimensional (2-D) analysis that does not guarantee a satisfactory design. Recently, several research efforts have been expended in the 3-D highway analysis with sight distance being the most researched area. Analytical models and computer software have been developed to accurately model 3-D daytime and nighttime sight distances. Roads designed using current 2-D standards may compromise safety or economy. Different models are currently available to simulate the forces acting on a vehicle in 3-D. These models show that the point-mass formula for modelling vehicle dynamics in the current standards can be inaccurate. Current standards contain recommendations for drainage of surface water, but explicit quantitative coordination of combined alignments is lacking. Furthermore, research is still needed to study the effect of alignment coordination on highway aesthetics and driver's perception of information.Key words: highway geometric design, three-dimensional analysis, sight distance, vehicle dynamics, drainage, highway aesthetics.

Computer Aided Geometric Design of Motion Interpolants

1991 ◽  
Author(s):  
Q. J. Ge ◽  
B. Ravani
Keyword(s):  
Computer Animation ◽  
Three Dimensional ◽  
Geometric Design ◽  
Computer Aided Geometric Design ◽  
Mapping Space ◽  
Three Dimensional Objects ◽  
Computer Aided ◽  
Point Interpolation ◽  
Curvature And Torsion ◽  
Spatial Kinematics

Abstract This paper studies continuous computational geometry of motions and develops a method for Computer Aided Geometric Design (CAGD) of motion interpolants. The approach uses a mapping of spatial kinematics to convert the problem of interpolating displacements to point interpolation in the space of the mapping. To facilitate the point interpolation, the previously non-oriented mapping space is made orientable. Methods are then developed for designing spline curves in the mapping space with tangent, curvature and torsion continuities. The results have application in computer animation of three dimensional objects used in computer graphics, computer vision and simulation of mechanical systems.

Computer Aided Geometric Design of Motion Interpolants

1994 ◽  
Vol 116 (3) ◽  
pp. 756-762 ◽  
Author(s):  
Q. J. Ge ◽  
B. Ravani
Keyword(s):  
Computer Animation ◽  
Three Dimensional ◽  
Geometric Design ◽  
Computer Aided Geometric Design ◽  
Mapping Space ◽  
Three Dimensional Objects ◽  
Spline Curves ◽  
Computer Aided ◽  
Curvature And Torsion ◽  
Spatial Kinematics

This paper studies continuous computational geometry of motion and develops a method for Computer Aided Geometric Design (CAGD) of motion interpolants. The approach uses a mapping of spatial kinematics to convert the problem of interpolating displacements to that of interpolating points in the space of the mapping. To facilitate the point interpolation, the previously unorientable mapping space is made orientable. Methods are then developed for designing spline curves in the mapping space with tangent, curvature and torsion continuities. The results have application in computer animation of three-dimensional objects used in computer graphics, computer vision and simulation of mechanical systems.

Analytical Model for Sight Distance Analysis on Three-Dimensional Highway Alignments

1996 ◽  
Vol 1523 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Yasser Hassan ◽  
Said M. Easa ◽  
A. O. Abd El Halim
Keyword(s):  
Three Dimensional ◽  
The Finite Element Method ◽  
Horizontal Curve ◽  
Design Standards ◽  
New Model ◽  
Distance Analysis ◽  
Horizontal Curves ◽  
Sight Distance ◽  
Proposed Model ◽  
Standards And Guidelines

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.

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.

Three-Dimensional, Probabilistic Highway Design

2008 ◽  
Vol 2060 (1) ◽  
pp. 10-18 ◽  
Author(s):  
Mohamed Sarhan ◽  
Yasser Hassan
Keyword(s):  
Reliability Analysis ◽  
Probabilistic Approach ◽  
Three Dimensional ◽  
Design Parameters ◽  
Horizontal Curve ◽  
Vertical Alignment ◽  
Highway Design ◽  
Side Slope ◽  
Sight Distance ◽  
Stopping Sight Distance

The potential usefulness of reliability analysis has recently been stressed in many engineering applications. Given the variability in the design parameters, a reliability-based probabilistic approach is well suited to replace the current deterministic highway design practice. However, progress in this regard is generally slow. In this study, the reliability analysis was used to estimate the probability of hazard (POH) that might result from insufficiency of sight distances. As an application, the available sight distance was checked against required stopping sight distance on an assumed road segment. Variation of the design parameters was addressed with Monte Carlo simulation using 100,000 sets of design parameters based on distributions available in the literature. A computer program was developed to use these sets of design parameters to calculate the profiles of available and required stopping sight distances in two- and three-dimensional projections as well as the profile of POH. The approach was applied to a horizontal curve overlapping with flat grade, crest curves, and sag curves in a cut section where the side slope would restrict the sightline. The analysis showed that the current deterministic approach yields very conservative estimates of available and required stopping sight distance, resulting in very low POH. The application example also showed the change of POH with the change of vertical alignment parameters.

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 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.

Sign in / Sign up

Export Citation Format

Share Document