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Citation |
Neuman TR. Transp. Res. Rec. 1989; 1208: 14-22. |
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Copyright |
(Copyright © 1989, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing) |
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DOI |
unavailable |
PMID |
unavailable |
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Abstract |
Design for stopping sight distance (SSD) is among the most basic, critical considerations in the total design of a highway. SSD requirements affect all geometric elements--horizontal and vertical alignment and cross section. Despite the importance of SSD, there is continuing, growing dissatisfaction among many design engineers with the current policy and general approach toward SSD. Such dissatisfaction can be attributed to the problems and costs of meeting current design policy, which have changed in recent years, coupled with a lack of evidence of the safety effectiveness of the policy. This paper presents a new approach to SSD design. It involves the abandonment of the concept that a single operational model for SSD is appropriate for all highway types under all conditions. Instead, the approach presented here suggests functional highway classification as the foundation for determining SSD design policy and values. A range of different operational models and driver, vehicle, and roadway parameters would be possible for different classes of highways. This, in turn, allows a range of design values for SSD for a given design speed, rather than just one value for all conditions. The paper presents examples of such models, with assumed values for driver reaction time, pavement friction, and object height. Illustrative calculations of SSD for five different classes of highways are shown. The calculations indicate the potential for SSD design values to vary significantly from those currently shown by the AASHTO policy. Language: en |
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Keywords |
Vision; Highway Systems; Roads and Streets--Visibility; Transportation--Accident Prevention; Highway Engineering--Standards |