A practical procedure was developed that explicitly considers the driving behavioral and safety rules of a horizontal alignment for the evaluation of roadway new designs; redesigns; and projects of rehabilitation, restoration, and resurfacing. Design classes were developed to classify, from a traffic safety point of view, roadway sections as good, fair, or poor; these design classes are associated with three safety criteria to develop an overall quantitative safety evaluation procedure for two-lane rural roads. The safety criteria are introduced to analyze and evaluate by (a) Safety Criterion (SC) I: the difference between design speed and actual driving behavior as expressed by variations in observed 85th percentile speed; (b) SC II: the difference between observed 85th percentile speeds on successive design elements; and (c) SC III: the difference between side-friction assumed and side-friction demanded at the 85th percentile speed level on curves. Furthermore, the issues discussed include design speed,...

Safety evaluation process for two-lane rural roads: a 10-year review

Stopping sight distance is an important design parameter in that it defines the minimum sight distance that must be provided at all points along the highway. Thus, it influences geometric design values, construction costs, and highway safety. Stopping sight distance is defined as the sum of two components - brake reaction distance and the braking distance. The basic model for calculating stopping sight distances was formalized in 1940, and the model's parameters have been altered to compensate for changes in eye height, object height, and driver behavior over the past 50 years. Recent studies, however, question whether the model's parameters and assumptions represent real-world conditions. This paper presents a new model for determining stopping sight distance requirements for geometric design of highways. The new model is based on parameters describing driver and vehicle capabilities that can be validated with field data and defended as safe driving behavior. More than 50 drivers, 3,000 braking maneuvers, 1,000 driver eye heights, and 1,000 accident narratives were used in developing the recommended parameter values for the new model. The recommended values are attainable by most drivers, vehicles, and roadways. The new model results in stopping sight distances, sag vertical curve lengths, and lateral clearances that are between the current minimum and desirable requirements, and crest vertical curve lengths that are shorter than current minimum requirements.

A new stopping sight distance model for use in highway geometric design

http://owsgip.itc.utwente.nl/projects/complex/images/uploaded_files/Voinov_et_al-Journal_of_Cleaner_Production.pdf

Estimating the potential of roadside vegetation for bioenergy production

Passing maneuvers allow faster drivers to continue driving at their desired speeds without being delayed behind impeding vehicles. On two-lane rural roads, such maneuvers require the passing driver to occupy the opposing lane; this condition has tremendous implications for the safety and operation of two-lane roads. Several studies have investigated the passing behavior of drivers, and some studies have used driving simulators to analyze drivers’ behavior during following and passing maneuvers. However, the validity of simulators has not been ensured, because their results have rarely been compared with real data. The objective of this study was to compare drivers’ passing behavior as observed in the field with passing behavior in a driving simulator. For this purpose, data on passing performance and passing gap acceptance decisions were required. The study carried out a comparative analysis of the most significant variables related to passing behavior. The results showed similarities between passing time...

/pdf/passing-behavior-on-two-lane-roads-in-real-and-simulated-2aptrnn44t.pdf

Passing Behavior on Two-Lane Roads in Real and Simulated Environments

Stopping sight distance is an important design parameter in that it defines the minimum sight distance that must be provided at all points along the highway. Thus, it influences geometric design values, construction costs, and highway safety. Stopping sight distance is defined as the sum of two components—brake reaction distance and braking distance. The basic model for calculating stopping sight distances was formalized in 1940, and the model's parameters have been altered to compensate for changes in eye height, object height, and driver behavior over the past 50 years. Recent studies, however, question whether the model's parameters and assumptions represent real-world conditions. A new model for determining stopping sight distance requirements for geometric design of highways is presented. This model is based on parameters describing driver and vehicle capabilities that can be validated with field data and defended as safe driving behavior. More than 50 drivers, 3,000 braking maneuvers, 1,000 driver e...

New Stopping Sight Distance Model for Use in Highway Geometric Design

This paper reviews the geometric design practices related to sight distance of a number of countries The purpose of this paper is to present the sight distance design practices of a variety of countries as a resource to highway agencies in any country that may be considering possible modifications and updates to their own policies and practices It is hoped that this paper will serve as a resource presenting ideas and concepts that may be new to some, but are in actual use elsewhere in the world International exchanges of this type of information are valuable in that they provide practicing engineers and researchers with a perspective that goes beyond their own country and their own part of the world The ability to see ahead and observe potentially conflicting traffic is critical to safe highway operations Sight distance, an important element in the geometric design of highways, refers to the length of roadway over which a driver has an unobstructed view This paper deals with the criteria used in geometric design for three key aspects of sight distance: (1) stopping sight distance; (2) passing sight distance; and (3) intersection sight distance Each of these types of sight distance is discussed in this paper

H. Joubert

Papers

International sight distance design practices