Survey and Design Consistency Evaluation in Two-Lane Rural Road Segments

The present research proposes a time and cost-effective methodology to survey and perform a design consistency evaluation in two-lane rural road segments. The implementation of the proposed methodology carried out in Central Greece and more particularly along the national road Volos-Karditsa, from the local community Mikrothives up to the entrance of the Volos municipal unit. The road survey methodology, the process of creating the terrain model as well as the cross-check between the designed road with the requirements included in the Greek Road Design Guidelines Manual-Chapter X, are analytically presented. Similar checks are also performed for the sight distance throughout the road segments aiming to enable the rehabilitation of existing rural roads and enhance their safety level. The design of the road was followed by the execution of an experiment with the participation of a motorcycle rider aiming at the recording of his trajectory throughout the road which was then compared with its geometry. The experiment carried out by exploiting an instrumented vehicle and GPS technology. Several conclusions were drawn regarding the encroachment of the centerline and the deviation from the theoretical trajectory in the middle of the travelled way. Subsequently, the proposed methodology provides a reliable and simple solution of surveying and evaluating a 2-lane rural road in safety terms.

Three-dimensional GIS-based approach for highway design 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.

Evaluation of driver visual demand at different traffic volumes on complex two-dimensional multi-lane highway alignments.

This research focuses on evaluating driver visual demand at different traffic volumes along with geometric design features for two-dimensional (2D) multi-lane highways consisting of horizontal and vertical alignments which is a crucial part of highway design consistency research. Three such alignments, with simple and complex curves were designed to generate desired traffic volume levels. A driving simulator was used to collect date from twenty drivers that participated in roadway alignment experiments at Ryerson University. Statistical Analysis Software (SAS) was used to analyze and process output data. Models were developed for visual demand and volume/capacity ratios, and geometric characteristics of the road, where visual demand was the only dependent variable. The research found that a relationship exists between visual demand and different traffic volumes along with geometric characteristics of the road.

Evaluation of driver visual demand at different traffic volumes on complex two-dimensional multi-lane highway alignments.

This research focuses on evaluating driver visual demand at different traffic volumes along with geometric design features for two-dimensional (2D) multi-lane highways consisting of horizontal and vertical alignments which is a crucial part of highway design consistency research. Three such alignments, with simple and complex curves were designed to generate desired traffic volume levels. A driving simulator was used to collect date from twenty drivers that participated in roadway alignment experiments at Ryerson University. Statistical Analysis Software (SAS) was used to analyze and process output data. Models were developed for visual demand and volume/capacity ratios, and geometric characteristics of the road, where visual demand was the only dependent variable. The research found that a relationship exists between visual demand and different traffic volumes along with geometric characteristics of the road.

Dual-Lane Roundabouts Geometric Design for Optimum Design Consistency and Operation

Dual-lane roundabouts successfully controlling traffic because of their slower entry speeds and fewer conflict points compared to conventional intersections. Operational evaluations of dual-lane roundabouts depend on the average delay at each roundabout entry, and the delay of each entry depends on the entry capacity. An optimization model is developed in this thesis for dual-lane right-angle and skewed-angle roundabouts, which determines the design elements of the roundabout based on design consistency and the least average intersection delay. The design element includes vehicle radii for through, left, and right turn traffic paths. The design consistency of an individual path is considered by minimizing the relative speed difference along each vehicle path for all approaches. Operational analysis gives an estimation of the capacity and level of service in terms of queue length and delay. These models use site conditions as inputs and prove the feasibility of the design.

Evaluation of driver visual demand at different design speeds on complex two-dimensional rural highway alignments

Road crashes are a major cause of loss of human life, property and money throughout the world. One of the reasons behind these crashes is the interaction between drivers and road alignments. The need to understand the factors that affect drivers has become obvious and is now being addressed by researchers. Moreover, driver workload is gaining attention as a measure of highway-design consistency as it directly reveals design features to the driver. This research focuses on evaluating driver visual demand at different design speeds along with other geometric design features for two-dimensional rural horizontal roadway alignments. Twelve such alignments having simple and complex curves were designed following the standards of the American Association of Highway and Transportation Officials (AASHTO) and the Transportation Association of Canada (TAC). The driver simulator at Ryerson University, Toronto, recently modified after the integration of a car, was used for the simulation of roadway alignments. Scenario Definition Language (SDL) was used to develop Event files for simulation and to save the required data. Twelve drivers drove the simulated alignments. The output data relating to driver visual demand were processed using MS Notepad and MS Excel. The visual demand calculations for full-element length (VDF), half-element length (VDH) and the first 30 m of element length (VD30) for curve and tangent sections of alignments were done using MS Excel. Statistical Analysis Software (SAS) was used to anlayze and develop models for VDF, VDH and VD30 for curve and tangent sections, first considering design speed only as explanatory variable and then considering design speed along with other geometric design characteristics as explanatory variables. It has been observed that visual demand increases with the increase in design speed. Besides, the combined effect of design speed an other geometric design characteristics (e.g., the type of preceding element, the turning direction of a curve) has significant effect on visual demand. It was also found that visual demand followed a Log Normalized distribution which was also observed by previous research. The developed models were used to establish the visual demand profile for highway design consistency evaluation. The comparison of visual demand profile and operating speed profile has shown that the visual demand can be an acceptable measure for evaluating the highway design consistency.

Geometric design of single-lane roundabouts for optimum consistency and operation

The objectives while designing roundabout is design consistency and operational performance. Design consistency affects roundabout safety while operational performance affects its level of service. Along with design consistency, roundabout will be more safe if its geometry forces traffic to enter and circulate at less than specified design speed. Vehicle path radii control speeds at each vehicle path. Vehicle path radii are traditionally obtained from drawing freehand each vehicle paths on proposed roundabout geometry. Existing design approaches for roundabouts use a trial-and-error procedure to choose the design parameters in order to satisfy design standards. With this approach it is quite complicated to satisfy design guidelines and site conditions at the same time. A minor change in geometry can result in significant changes in safety and operational performance. Therefore, many iterations of geometric layout would be required to evaluate safety and operational analysis at given traffic conditions. Designer needs to revise and refine the initial geometric layout to enhance safety and its operational performance. In this thesis, an optimization model is developed that predicts optimum design parameters with multiple objectives: maximum design consistency and minimum average intersection delay. At optimum design parameters, this model also provides vehicle path radii for each path. These vehicle path radii were used to predict operating speed along each path using an existing operating speed prediction model. The optimization model takes site conditions as input and satisfies the two objectives for given traffic and geometric conditions. This is a new approach of optimum design of single-lane roundabouts with four legs intersecting at right angle. The model not only satisfies the two objectives, but also limits the operating speed along each path (left, through, and right), below the specified design speed of roundabout.

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

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.

Improved methods for distribution of superelevation

The American Association of State Highway and Transportation Officials (AASHTO) provide 5 methods for distributing highway superelevation (e) and side friction (f). Method 1 (linear) is inferior to Method 5 (curvilinear). AASHTO Method 5 deals with speed variations, but its complex mathematical calculation affects design consistency. Safety margin is the difference between design and maximum limiting speed. This thesis describes distribution of superelevation (e) and side friction factor (f) based on the EAU and SAU methods using AASHTO and two different curves from the unsymmetrical curve; the equal parabolic arcs "EAU Curve" and a single arc unsymmetrical curve "SAU Curve". The thesis also describes e and f distributions based on the optimization model. The EAU and SAU methods and Parametric Cubic Optimization Model improve highway design consistency based on safety margins. Examples show the methods and optimization model are superior to AASHTO methods.