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Highway-freeway interchanges can be a source of confusion to unfamiliar drivers. Typically, freeway entrance ramp information is provided by means of trailblazer assemblies (interstate or highway shield, cardinal direction, and a small white arrow on a blue shield). Trailblazer assemblies are generally located right at the interchange location, giving unfamiliar drivers very little advance notification as to the proper lane choice needed to gain access to the freeway entrance. Advance located ground mounted diagrammatic guide signs provide this much needed information well in advance of the interchange entrance, thus giving drivers more time to change lanes, if needed. Diagrammatic signs have been used in Europe for many years with great success. The present study investigated the effectiveness of ground mounted diagrammatic signs in the context of urban multi-lane arterials leading to a freeway. The diagrammatic sign layout was designed as part of this project in collaboration with ODOT. Six highway-freeway interchanges were selected in the Greater Columbus, Ohio, area to determine the effectiveness of the diagrammatic signs in the field. Traffic flow video footage was collected at the selected sites before the diagrammatic signs were installed. The finalized diagrammatic sign designs were then installed and the traffic flow videotaping was repeated. The collected video footage was automatically analyzed with Mobilizer PC. The resulting vehicle count, speed, and headway data was used as input to a closed form analytical model to determine the probability that drivers could successfully change lanes as needed, prior to reaching the gore of the freeway entrance. The theoretical analysis indicated a much higher probability that an unfamiliar driver could execute a required lane change when diagrammatic signs are used. ODOT/FHWA evaluators visited the six interchange sites and provided their input and opinions as to the use of diagrammatic signs. The vast majority of the evaluators fully embraced the idea of diagrammatic signs. Eye movement recordings were performed at night at the six sites in order to determine if the presence of the diagrammatic signs was distracting. The results of the eye movement analysis indicate that the diagrammatic signs are not looked at excessively often or excessively long. The overall median first look distance to the diagrammatic signs was found to be 125m. An evaluation with unfamiliar test drivers corroborated the findings of the theoretical model analysis, in that drivers were able to execute a needed lane change much earlier when diagrammatic signs were provided. A set of application guidelines for diagrammatic signs is provided.
Effective use of driving simulators requires considerable technical and methodological skill along with considerable background knowledge. Acquiring the requisite knowledge and skills can be extraordinarily time consuming, yet there has been no single convenient and comprehensive source of information on the driving simulation research being conduc
(a) Design and construction. (1) Each facility or part of a facility constructed by, on behalf of, or for the use of a public entity shall be designed and constructed in such manner that the facility or part of the facility is readily accessible to and usable by individuals with disabilities, if the construction was commenced after January 26, 1992. (2) Exception for structural impracticability. (i) Full compliance with the requirements of this section is not required where a public entity can demonstrate that it is structurally impracticable to meet the requirements. Full compliance will be considered structurally impracticable only in those rare circumstances when the unique characteristics of terrain prevent the incorporation of accessibility features. (ii) If full compliance with this section would be structurally impracticable, compliance with this section is required to the extent that it is not structurally impracticable. In that case, any portion of the facility that can be made accessible shall be made accessible to the extent that it is not structurally impracticable. (iii) If providing accessibility in conformance with this section to individuals with certain disabilities (e.g., those who use wheelchairs) would be structurally impracticable, accessibility shall nonetheless be ensured to persons with other types of disabilities, (e.g., those who use crutches or who have sight, hearing, or mental impairments) in accordance with this section.
This document presents a synthesis of current information and operating practices related to roadside safety and is developed in metric units. The roadside is defined as that area beyond the traveled way (driving lanes) and the shoulder (if any) of the roadway itself. The focus of this guide is on safety treatments that minimize the likelihood of serious injuries when a driver runs off the road. This guide replaces the 1989 AASHTO "Roadside Design Guide."
TRB's National Cooperative Highway Research Program (NCHRP) Report 672: Roundabouts: An Informational Guide - Second Edition explores the planning, design, construction, maintenance, and operation of roundabouts. The report also addresses issues that may be useful in helping to explain the trade-offs associated with roundabouts. This report updates the U.S. Federal Highway Administration's Roundabouts: An Informational Guide, based on experience gained in the United States since that guide was published in 2000.
Expectancy relates to a driver's readiness to respond to situations, events, and information in predictable and successful ways. This report describes the concept of driver expectancy in the context of the driving task, and provides examples of expectancy and expectancy violations. It includes a procedure for identifying general and specific expectancy violations to enable engineers to develop remedial treatments to deal with expectancy problems.