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.

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.

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.

scholarly journals Studying the effect of spiral curves and intersection angle, on the accident ratios in two-lane rural highways in Iran

2013 ◽  
Vol 25 (4) ◽  
pp. 343-348 ◽  
Author(s):  
Mohammad Hossain Jalal Kamali ◽  
Mohammad Saeed Monajjem ◽  
Mohammad Sadegh Ayubirad
Keyword(s):  
Transportation Engineering ◽  
Intersection Angle ◽  
Highway Design ◽  
Rural Highways ◽  
Horizontal Curves ◽  
Accident Rates

Safety in highways is one of the most important subjects in Transportation Engineering. Increasing rate of vehicles and the needs to design or geometrically modifying the highways, emphasized on the safe-designing of the roadways more than before. Between the constructive components of the highway, horizontal curves due to the more occurrences of accidents are of great importance. The American ministry of highway and transportation introduced the software IHSDM, with variant capabilities, to predict accidents. In this research, five types of curves (simple circle curve and clothoid-circle-clothoid) at different intersection angles were designed, and accident rates based on the standard specifications on each curve was predicted by using the IHSDM, and the results are compared with each other. Finally, by processing the curves of accident rates versus the curves types and intersection angle, and comparing them with each other, the necessity of using spiral curves in the highway design is emphasized.

Improved speed-profile model for two-lane rural highways

2003 ◽  
Vol 30 (6) ◽  
pp. 1055-1065 ◽  
Author(s):  
Said M Easa
Keyword(s):  
Highway Safety ◽  
Extended Model ◽  
Speed Profile ◽  
Rural Highways ◽  
Profile Model ◽  
Horizontal Curves ◽  
Sight Distance ◽  
Safety Design ◽  
Speed Change ◽  
Design Consistency

The speed-profile model has been suggested as a valuable tool for evaluating geometric design consistency for two-lane rural highways with isolated and combined horizontal and vertical alignments. The model determines the operating speeds on the speed-change (SC) segment, which is the distance between speed-limiting curves. The speed-limiting curves are the horizontal curves and the limited sight-distance crest vertical curves on horizontal tangents, where the sight distance required by the design guides is not satisfied. The model assumes that deceleration begins where required, which implies that the next curve is visible when deceleration starts. This paper presents an extension to the speed-profile model to incorporate the effect of sight obstruction on operating speeds and deceleration rates. The SC segment may include nonlimited sight–distance crest vertical and sag vertical curves. These curves may present sight obstruction. A procedure to determine whether the sight line is obstructed is developed. If it does, simple formulas are applied for revising the operating-speed profile. The extended model is suitable for inclusion in the design consistency module of the interactive highway safety design model.Key words: speed profile, model, two-lane highways, alignments, design consistency.

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.

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.

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.

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