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 Three-dimensional GIS-based approach for highway design consistency evaluation

2021 ◽  
Author(s):  
Yingfeng Li
Keyword(s):  
Traffic Safety ◽  
3D Visualization ◽  
Three Dimensional ◽  
Evaluation Methodology ◽  
Evaluation Procedure ◽  
Highway Design ◽  
Great Ability ◽  
Related Data ◽  
Design Consistency ◽  
Consistency Evaluation

The mission of transportation is to transport people and goods safely and efficiently. Therefore, traffic safety has been one of the most important topics since the birth of the subject of transportation. Improving highway design consistency is considered as an important strategy for improving traffic safety. Geographic information systems (GIS) has been popular for decades due to its great ability to deal with spatial or spatially-related data. Contributions from GIS to transportation have become well known in some aspects. However, GIS, especially its 3D visualization function, has not, in previous studies, been integrated into the core of the highway design consistency evaluation procedure. In contrast, the major objective of this thesis research is to integrate the latest advanced GIS techniques including its 3D visualization function and the state-of-the-art knowledge from previous studies into the highway design consistency evaluation procedure. By adding new functions specifically developed for highway design consistency evaluation, a 3D GIS-based highway design consistency evaluation methodology is developed. This newly developed methodology and associated software tools, as a combination of GIS, including its 3D visualization function, and highway consistency modules, will make significant contributions in the following aspects: highly automated consistency evaluation procedure, 3D-alignment-based consistency level analysis, impressive evaluation result presentation, and spatially based consistency improvement suggestion. Verification of this methodology on a typical 3D-highway segment in Ontario shows very promising results. This study, to a great extent, is convincing that, in the near future, designers could be able to design highways in a regular GIS environment.

scholarly journals Evaluation of Driver Visual Demand on Three-Dimensional Rural Highway Alignments

2021 ◽  
Author(s):  
Wen Long He
Keyword(s):  
Driving Simulator ◽  
3D Visualization ◽  
Three Dimensional ◽  
Highway Design ◽  
K Value ◽  
Rural Highways ◽  
State Highway ◽  
Demand Models ◽  
Driver Workload ◽  
Design Consistency

This research focuses on evaluating driver visual demand on three-dimensional (3D) highway alignments consisting of combined horizontal and vertical alignments which is an important part of highway design consistency research. Using a driving simulator, ten hypothetical 2D and 3D alignments for two-lane rural highways were developed, following the standard guidelines of the Transportation Association of Canada (TAC) and the American Association of State Highway Transportation Officials (AASHTO). Fifteen driver subjects drove in the simulator. The data relating to visual demand information were processed and analysed using Microsoft Excel and SAS statistical software. The results indicated that visual demand on 3D curves varies widely with the inverse of radius of horizontal curvature and the inverse of K value of vertical curvature. Age played another important role on visual demand. Models for evaluating visual demand on 3D highway alignments were developed for curves and tangents. The models developed in this study have been applied to horizontal and 3D alignments to carry out a design consistency evaluation. In addition, GIS virtual reality technique was applied to present the visual demand results for a real highway on the 3D visualization model. 3D visualization not only offers a better understanding of driver workload along the highway, but also represents an important tool to effectively manage information.

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 Three-dimensional GIS-based approach for highway design consistency evaluation

2021 ◽  
Author(s):  
Yingfeng Li
Keyword(s):  
Traffic Safety ◽  
3D Visualization ◽  
Three Dimensional ◽  
Evaluation Methodology ◽  
Evaluation Procedure ◽  
Highway Design ◽  
Great Ability ◽  
Related Data ◽  
Design Consistency ◽  
Consistency Evaluation

The mission of transportation is to transport people and goods safely and efficiently. Therefore, traffic safety has been one of the most important topics since the birth of the subject of transportation. Improving highway design consistency is considered as an important strategy for improving traffic safety. Geographic information systems (GIS) has been popular for decades due to its great ability to deal with spatial or spatially-related data. Contributions from GIS to transportation have become well known in some aspects. However, GIS, especially its 3D visualization function, has not, in previous studies, been integrated into the core of the highway design consistency evaluation procedure. In contrast, the major objective of this thesis research is to integrate the latest advanced GIS techniques including its 3D visualization function and the state-of-the-art knowledge from previous studies into the highway design consistency evaluation procedure. By adding new functions specifically developed for highway design consistency evaluation, a 3D GIS-based highway design consistency evaluation methodology is developed. This newly developed methodology and associated software tools, as a combination of GIS, including its 3D visualization function, and highway consistency modules, will make significant contributions in the following aspects: highly automated consistency evaluation procedure, 3D-alignment-based consistency level analysis, impressive evaluation result presentation, and spatially based consistency improvement suggestion. Verification of this methodology on a typical 3D-highway segment in Ontario shows very promising results. This study, to a great extent, is convincing that, in the near future, designers could be able to design highways in a regular GIS environment.

scholarly journals Evaluation of Driver Visual Demand on Three-Dimensional Rural Highway Alignments

2021 ◽  
Author(s):  
Wen Long He
Keyword(s):  
Driving Simulator ◽  
3D Visualization ◽  
Three Dimensional ◽  
Highway Design ◽  
K Value ◽  
Rural Highways ◽  
State Highway ◽  
Demand Models ◽  
Driver Workload ◽  
Design Consistency

This research focuses on evaluating driver visual demand on three-dimensional (3D) highway alignments consisting of combined horizontal and vertical alignments which is an important part of highway design consistency research. Using a driving simulator, ten hypothetical 2D and 3D alignments for two-lane rural highways were developed, following the standard guidelines of the Transportation Association of Canada (TAC) and the American Association of State Highway Transportation Officials (AASHTO). Fifteen driver subjects drove in the simulator. The data relating to visual demand information were processed and analysed using Microsoft Excel and SAS statistical software. The results indicated that visual demand on 3D curves varies widely with the inverse of radius of horizontal curvature and the inverse of K value of vertical curvature. Age played another important role on visual demand. Models for evaluating visual demand on 3D highway alignments were developed for curves and tangents. The models developed in this study have been applied to horizontal and 3D alignments to carry out a design consistency evaluation. In addition, GIS virtual reality technique was applied to present the visual demand results for a real highway on the 3D visualization model. 3D visualization not only offers a better understanding of driver workload along the highway, but also represents an important tool to effectively manage information.

Establishing highway horizontal alignment to maximize design consistency

2007 ◽  
Vol 34 (9) ◽  
pp. 1159-1168 ◽  
Author(s):  
Said M Easa ◽  
Atif Mehmood
Keyword(s):  
Geometric Features ◽  
Trial And Error ◽  
Highway Design ◽  
Rural Highways ◽  
Physical Constraints ◽  
Horizontal Alignment ◽  
Horizontal Curves ◽  
Decision Variables ◽  
Acceleration And Deceleration ◽  
Design Consistency

Highway design consistency is one of the important criteria in selecting the geometric features of proposed or existing alignments of two-lane rural highways. Operating-speed (OS) profile models have been used to evaluate design consistency by trial and error. For a proposed new highway, however, there may be geometric and physical constraints, and selection of these elements by trial and error to achieve optimal design consistency would be difficult, if not impossible. This paper presents an optimization model that establishes highway horizontal alignment to achieve maximum design consistency based on the OS profile. The decision variables of the model include radius of horizontal curves, spiral curve lengths, length of speed-change (SC) segments, and acceleration and deceleration rates. The objective function of the model minimizes the mean OS difference or the maximum OS difference for successive geometric features along the highway section. Application examples and sensitivity analysis are presented to illustrate the capabilities of the model in evaluating improvement strategies and to ensure that the model produces sound optimum alignments. The proposed model, which complements existing optimization models that mainly address highway construction cost, should be of interest to highway practitioners and engineers.Key words: design consistency, highway, geometric, horizontal alignment, optimization modeling, speed profile.

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.

Continuous Speed Profiles to Investigate Drivers' Behavior on Two-Lane Rural Highways

2015 ◽  
Vol 2521 (1) ◽  
pp. 3-11 ◽  
Author(s):  
Alfonso Montella ◽  
Francesco Galante ◽  
Filomena Mauriello ◽  
Massimo Aria
Keyword(s):  
Driving Simulator ◽  
Prediction Models ◽  
Piecewise Linear ◽  
Small Radius ◽  
Operating Speed ◽  
Data Set ◽  
Highway Design ◽  
Rural Highways ◽  
Acceleration And Deceleration ◽  
Design Consistency

To improve highway design consistency, several studies developed operating speed prediction models and investigated drivers' speed behavior. Most existing models are based on spot speed data that assume constant operating speed throughout the horizontal curves and occurrence of acceleration and deceleration only on tangents. To overcome limitations associated with existing models, this study investigated continuous speed profiles with an experiment that used a high-fidelity dynamic-driving simulator on a two-lane highway. A piecewise linear regression model and locally weighted regression scatter-plot smoothing were used to remove noise in the data set while preserving underlying patterns and to identify significant changes in the speed profile. Based on the smoothed speed profiles, models to predict operating speed in curves and in tangents, deceleration and acceleration rates to be used in the operating speed profiles, and starting and ending points of constant operating speed in curve were developed. Radius of the curve notably affected not only the operating speed in the curve but also the operating speed of the tangent following the curve: the smaller the radius, the lower the operating speed of the exit tangent. Both acceleration and deceleration rates increased with curvature. This study found that operating speed was not constant along curves. On small radius curves, deceleration ended close to the center of the curve, and acceleration starts, close to the end of the curve. Increasing the curve radius, the end point of deceleration moves toward the curve's beginning, whereas the start of acceleration moves toward the center of the curve.

Effect of geometric design consistency on road safety

2004 ◽  
Vol 31 (2) ◽  
pp. 218-227 ◽  
Author(s):  
Joanne C.W Ng ◽  
Tarek Sayed
Keyword(s):  
Road Safety ◽  
Prediction Models ◽  
Model Development ◽  
Geometric Design ◽  
Highway Design ◽  
Rural Highways ◽  
Accident Prediction ◽  
Design Characteristics ◽  
Design Consistency ◽  
The Impact

Geometric design consistency is emerging as an important rule in highway design. Identifying and treating any inconsistency on a highway can significantly improve its safety performance. Considerable research has been undertaken to explore this concept including identifying potential consistency measures and developing models to estimate them. However, little work has been carried out to quantify the safety benefits of geometric design consistency. The objectives of this study are to investigate and quantify the relationship between design consistency and road safety. A comprehensive accident and geometric design database of two-lane rural highways is used to investigate the effect of several design consistency measures on road safety. Several accident prediction models that incorporate design consistency measures are developed. The generalized linear regression approach is used for model development. The models can be used as a quantitative tool for the evaluation of the impact of design consistency on road safety. An application is presented where the ability of accident prediction models that incorporate design consistency measures is compared with those that rely on geometric design characteristics. It is found that models that explicitly consider design consistency may identify the inconsistencies more effectively and reflect the resulting impacts on safety more accurately than those that do not.Key words: geometric design consistency, road safety, quantification, accident prediction models.

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.

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