00753984

Component

https://doi.org/10.3141/1612-03

http://scholar.google.com...alim&publication_year=1998

Highway geometric design has usually been considered in separate two-dimensional (2-D) projections of horizontal and vertical alignments. Such a practice was followed mainly because three-dimensional (3-D) analysis of combined highway alignments was expected to be difficult. As a result, the effect of ignoring the 3-D nature of the highway alignment could not be quantified. With the long-term objective of developing 3-D design practice, a framework for 3-D highway geometric design was developed and 3-D sight distance was extensively studied as the first design basis. The status of sight distance in current design policies and previous research is summarized, and mainly 2-D analysis was considered. The five main tasks performed to cover the 3-D highway sight distance are presented. (a) As a preliminary step, the 2-D sight distance on complex separate horizontal and vertical alignments was modeled, and the finite element method was used for the first time in the highway geometric design. (b) The 2-D models were then expanded to cover the daytime and nighttime sight distances on 3-D combined alignments. (c) The analytical models were coded into computer software that can determine the available sight distance on actual highway segments. (d) The models were applied in 3-D design of combined horizontal and vertical curves in cut-and-fill sections, and preliminary design aids were derived. (e) Finally, a new concept of red zones was suggested to mark the locations on alignments designed according to current practices where the available sight distance will drop below that required. A comprehensive work on 3-D sight distance analysis has been compiled that should be of great importance for highway researchers and professionals.

This paper appears in Transportation Research Record No. 1612, Highway Geometric Design Issues.

English

p. 17-25

1998

Transportation Research Record

0309064570

Figures (5) ; References (19) ; Tables (5)

Alignment; Curves (Geometry); Finite element method; Geometric design; Highway design; Mathematical models; Sight distance; Software

Analytical models; Horizontal curvature; Two dimensional; Vertical curvature

Design; Highways; I20: Design and Planning of Transport Infrastructure

TRIS, TRB, ATRI

Sep 30 1998 12:00AM

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