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.

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.

Highway Alignment: Three-Dimensional Problem and Three-Dimensional Solution

1998 ◽  
Vol 1612 (1) ◽  
pp. 17-25 ◽  
Author(s):  
Yasser Hassan ◽  
Said M. Easa ◽  
A. O. Abd El Halim
Keyword(s):  
Three Dimensional ◽  
Computer Software ◽  
Geometric Design ◽  
Analytical Models ◽  
Dimensional Solution ◽  
Distance Analysis ◽  
Sight Distance ◽  
The Status ◽  
Current Design ◽  
Highway Alignment

Highway geometric design has usually been considered in separate two-dimensional (2-D) projections of horizontal and vertical alignments. Such a practice was followed mainly because three-dimensional (3-D) analysis of combined highway alignments was expected to be difficult. As a result, the effect of ignoring the 3-D nature of the highway alignment could not be quantified. With the long-term objective of developing 3-D design practice, a framework for 3-D highway geometric design was developed and 3-D sight distance was extensively studied as the first design basis. The status of sight distance in current design policies and previous research is summarized, and mainly 2-D analysis was considered. The five main tasks performed to cover the 3-D highway sight distance are presented. ( a) As a preliminary step, the 2-D sight distance on complex separate horizontal and vertical alignments was modeled, and the finite element method was used for the first time in the highway geometric design. ( b) The 2-D models were then expanded to cover the daytime and nighttime sight distances on 3-D combined alignments. ( c) The analytical models were coded into computer software that can determine the available sight distance on actual highway segments. ( d) The models were applied in 3-D design of combined horizontal and vertical curves in cut-and-fill sections, and preliminary design aids were derived. ( e) Finally, a new concept of red zones was suggested to mark the locations on alignments designed according to current practices where the available sight distance will drop below that required. A comprehensive work on 3-D sight distance analysis has been compiled that should be of great importance for highway researchers and professionals.

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.

Stopping Sight Distance and Available Sight Distance: New Model and Reliability Analysis Comparison

2017 ◽  
Vol 2638 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Jonathan S. Wood ◽  
Eric T. Donnell
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Design Criterion ◽  
Geometric Design ◽  
Design Criteria ◽  
Sight Distance ◽  
Stopping Sight Distance ◽  
Future Work ◽  
Important Design ◽  
Design Guidance

Stopping sight distance (SSD) is an important design criterion used in the geometry of highways and streets. Design guidance implies that SSD is used to ensure safety along the roadway. This paper reviews SSD design criteria and develops an updated model to improve consistency between available sight distance and SSD criteria found in geometric design policy. A new variable, the distance from the front of the car to the driver’s eye ( Lfront-eye), is used in the updated model. Distributional values for Lfront-eye are determined. A method accounting for lighted (daytime and lighted nighttime) versus unlighted nighttime conditions is also discussed. A probabilistic analysis of vertical curve SSD uses Monte Carlo simulation. The results of this analysis are compared with the SSD model found in current geometric design policy. Possible values for Lfront-eye that can be used in design guidance are proposed. Potential issues that should be investigated in future work are discussed.

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.

Impact of highway consistency on capacity utilization of two-lane rural highways

1999 ◽  
Vol 26 (6) ◽  
pp. 789-798 ◽  
Author(s):  
Gamal M Gibreel ◽  
Ibrahim A El-Dimeery ◽  
Yasser Hassan ◽  
Said M Easa
Keyword(s):  
Traffic Safety ◽  
Research Work ◽  
Three Dimensional ◽  
Capacity Utilization ◽  
3D Analysis ◽  
Horizontal Curve ◽  
Highway Capacity ◽  
Highway Design ◽  
Rural Highways ◽  
Design Consistency

Consistent highway design is expected to provide safe, economical, and smooth traffic operation. Several studies have been performed to investigate the effect of highway consistency on traffic safety. However, the relationship between design consistency and highway capacity and level of service has not been addressed in current research work and design practices. In addition, the effect of the three-dimensional (3D) nature of highway alignments was not considered, and design consistency was studied based solely on two-dimensional (2D) analysis of highway horizontal alignments. This paper presents a methodology to determine the effect of highway design consistency on highway capacity utilization based on 3D analysis. This methodology will help road designers to estimate highway capacity more accurately. The study was performed on two-lane rural highways in Ontario, where two types of 3D combinations were considered: a horizontal curve combined with a sag vertical curve (sag combination) and a horizontal curve combined with a crest vertical curve (crest combination). An additional adjustment factor that reflects the effect of highway design consistency on capacity utilization was developed. Different statistical models are introduced to estimate this factor based on geometric or traffic data. In addition, typical values of the consistency factor were developed based on an overall consistency evaluation criterion and can be easily used in capacity analysis.Key words: three-dimensional, alignments, capacity, geometric design, operating speed, design consistency.

scholarly journals Reliability-Based Analysis of Sight Distance Modelling for Traffic Safety

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
César de Santos-Berbel ◽  
Mohamed Essa ◽  
Tarek Sayed ◽  
María Castro
Keyword(s):  
Traffic Safety ◽  
Three Dimensional ◽  
Estimation Methods ◽  
Risk Level ◽  
Highway Design ◽  
Rural Highways ◽  
Horizontal Curves ◽  
Sight Distance ◽  
3D Methods ◽  
Geometric Elements

Sight distance is of the utmost importance for traffic safety. The consideration of three-dimensional (3D) available sight distance (ASD) in geometric design has been supported by several researchers. However, existing ASD estimation methods are two-dimensional (2D) in nature, which do not evaluate varying visibility conditions. This paper compares different methodologies of modelling the ASD. The ASD of 402 horizontal curves, located in twelve in-service two-lane rural highways, was analyzed. Three ASD estimation methods were used which include a 2D method and two different 3D methods. The ASD results obtained through 2D and 3D methodologies are compared. Also, the different conditions of the existing roadside features or geometric elements, under which the 3D ASD estimation is important, were identified. Next, reliability theory is utilized to evaluate the risk level (probability of noncompliance,Pnc) associated with limited sight distance for each ASD modelling method. The results of the comparison emphasized the importance of considering the 3D modelled sight distance when evaluating the associated risk either in highway design or during the service life. In addition, the results indicated that the ASD modelling approach can have a significant impact on the estimation of the safety of highway design.

scholarly journals Impacts of Different Driving Automation Levels on Highway Geometric Design from the Perspective of Trucks

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Shuyi Wang ◽  
Bin Yu ◽  
Yang Ma ◽  
Jinzhou Liu ◽  
Wen Zhou
Keyword(s):  
Traffic Safety ◽  
Geometric Design ◽  
Driving Safety ◽  
Innovative Technology ◽  
Design Elements ◽  
The Road ◽  
Positive Effects ◽  
Sight Distance ◽  
Automation Systems ◽  
On The Road

Truck automation is emerging as an innovative technology with benefits in traffic safety and the economy to revolutionize freight traffic. Despite these benefits, the potential negative or positive effects of different driving automation levels (from no automation to full automation) on highway geometry remained to be determined. In this study, differences related to sight distance characteristics among varied automation levels were firstly discussed and calibrated. Then, seven analysis scenarios of typical levels were proposed. Based on each level with tailored characteristics, the current models of geometric design elements including the required stopping sight distance, horizontal sight line offset, and lengths of vertical curves were revised. Finally, impacts of each level on computed values of those elements were evaluated. Results show that high or full driving automation could substantially lower the requirements of geometric design. Active safety systems have a similar role but with less significant effects. Differently, the driver assistance and partial or conditional automation systems put a higher demand on the road geometric design in terms of driving safety. Outcomes of this study can be used to design real-world geometry of dedicated lanes and provide a methodological basis for the operation of different driving automation features.

An approach for auditing highway sections for safety improvements

1999 ◽  
Vol 26 (6) ◽  
pp. 724-735 ◽  
Author(s):  
Said M Easa ◽  
Yasser Hassan ◽  
Dennis Siczkar
Keyword(s):  
Traffic Safety ◽  
Three Dimensional ◽  
Evaluation Process ◽  
Mean Value ◽  
Road Maintenance ◽  
Pavement Rehabilitation ◽  
Rural Highways ◽  
Sight Distance ◽  
Long Run ◽  
Mto Process

The objective of this paper is to present a framework for the evaluation of traffic safety improvements on rural highways based on the existing process of the Ministry of Transportation of Ontario (MTO). The framework includes four steps to identify hazardous locations and determine the most feasible improvements. The framework was applied to a 2.2 km segment on Highway 17 (Ontario, Canada) to illustrate how the framework might be implemented in practice. The first step is defining the highway section to be studied. This section is usually a segment that was constructed in the same contract, and its surface conditions require major maintenance. The evaluation of traffic safety on sections that are undergoing major pavement rehabilitation will reduce the overall cost of road maintenance. The second step is to collect and analyze collision data, along with traffic and geometric data. The purpose of this step is to compare the actual number of collisions on the section with the expected long-run mean value and identify the causes of collisions. Based on this analysis, the third step identifies the possible improvements that would eliminate or minimize the number of collisions. These improvements can be as simple as signing improvement or as complex as a major realignment. Finally, these improvements are evaluated economically and environmentally. For this study, several sections of the Ministry of Transportation of Ontario, other ministries and levels of government, and interest groups participated in the evaluation process. A refined MTO process, currently being considered for implementation, is briefly described along with a discussion of its key features.Key words: evaluation, highway improvements, safety, three-dimensional alignments, sight distance, collision frequency.

Validation of a Belt Model for Prediction of Hub Forces from a Rolling Tire4

2009 ◽  
Vol 37 (2) ◽  
pp. 62-102 ◽  
Author(s):  
C. Lecomte ◽  
W. R. Graham ◽  
D. J. O’Boy
Keyword(s):  
Internal Pressure ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Prediction Method ◽  
Analytical Models ◽  
Beam Model ◽  
Impedance Boundary ◽  
Bending Waves ◽  
Tire Rotation ◽  
Three Dimensional Models

Abstract An integrated model is under development which will be able to predict the interior noise due to the vibrations of a rolling tire structurally transmitted to the hub of a vehicle. Here, the tire belt model used as part of this prediction method is first briefly presented and discussed, and it is then compared to other models available in the literature. This component will be linked to the tread blocks through normal and tangential forces and to the sidewalls through impedance boundary conditions. The tire belt is modeled as an orthotropic cylindrical ring of negligible thickness with rotational effects, internal pressure, and prestresses included. The associated equations of motion are derived by a variational approach and are investigated for both unforced and forced motions. The model supports extensional and bending waves, which are believed to be the important features to correctly predict the hub forces in the midfrequency (50–500 Hz) range of interest. The predicted waves and forced responses of a benchmark structure are compared to the predictions of several alternative analytical models: two three dimensional models that can support multiple isotropic layers, one of these models include curvature and the other one is flat; a one-dimensional beam model which does not consider axial variations; and several shell models. Finally, the effects of internal pressure, prestress, curvature, and tire rotation on free waves are discussed.

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